DOI: 10.1161/CIRCEP.114.001781
Telomere Length and the Risk of Atrial Fibrillation: Insights into the Role of
Biological versus Chronological Aging
Running title: Roberts et al.; Telomere Length and Atrial Fibrillation Risk
Jason D. Roberts, MD1; Thomas A. Dewland, MD1; James Longoria, MD2; Annette L.
Fitzpatrick, PhD3; Elad Ziv, MD4; Donglei Hu, PhD4; Jue Lin, PhD5; David V. Glidden,, PhD6;
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
Eliz
El
i ab
abet
ethh H. Blackburn,
et
Blaack
ckbu
bu
Bruce M. Psaty, MD, PhD7,8; Esteban G. Burchard, MD, MPH9,10; Elizabeth
PhD5; Jeffrey
rey E. Olgin
O
Olgin,
lgin
lg
in, MD
in
M 1; Susan R.
R Heckbert,
Heckbert MD
MD, PhD3,7,8; Gregory
Greg
gor
o yM
M. Marcus,
Marcus MD,
MD MAS1
1
Section of
o C
Cardiac
ardi
ar
diac
di
acc E
Electrophysiology,
lectro
oph
hyssiolo
ogy
gy, Di
Divisi
Division
sion
n ooff Ca
Card
Cardiology,
rdio
rd
iolo
io
l gy
lo
gy, De
Department
epa
p rt
r me
ment
ntt off Me
Medi
Medicine,
diicine
ne, 4In
Institute
nstiitu of
5
n s & Depa
netics
p rtmeent of Medicine,
pa
Meedi
d cine, Depa
Human Genetics
Department
Department
paart
r me
ment
n of Bioc
nt
Biochemistry
o hemistry
ry
y & Biophysics,
Bio
oph
p yssic
i s, 6Departm
Department
m of
Epidemiology
Biostatistics,
o & Bios
ogy
Bi
ios
osta
tati
ta
tiisttiiccs,
s, 9De
Department
D
part
pa
rtme
mentt of
o Medicine,
Med
e icin
ne,
e, 100De
Department
Depa
p rt
pa
rtme
m nt
me
nt ooff Bioengineering
B oe
Bi
oeng
ngin
ngin
inee
eeri
ee
ring
ri
n & Th
ng
Thera
Therapeutic
a
Univ
Un
iver
ersi
er
sity
ty of
of California
C li
Ca
lifo
forn
rnia
rn
ia San
San Francisco,
Fra
ranc
ncis
nc
isco
co,, San
co
San Francisco;
Fran
Fr
anci
an
cisc
scoo; 2Di
sc
Sciences, University
Division
Divi
viisi
sion
on ooff Ca
Card
Cardiovascular
rdio
iova
vasc
va
scul
sc
ullar S
Surgery,
urr
Sutter Health,
Sacramento,
a
alth,
Sacraame
m nt
n o,
o CA;
CA; 3De
Department
Depa
part
pa
r me
rt
ment
ntt of
of Epidemiology,
Epid
Ep
idem
id
emio
em
io
iolo
o ogy
gy,, 7Ca
Cardiovascular
Card
rdio
rd
iova
io
v sc
va
s ul
ular
ar Health
Hea
ealt
lthh Research Unit,
lt
8
University off Washington;
W hhii t
Departments
D
t
t off Medicine
M ddii i and
dH
Health
llth
th
hS
Services,
i
U
University
i
iitt off Washington
W hi
&
Group Health Research Institute, Group Health, Seattle, WA
Correspondence:
Gregory M. Marcus, MD, MAS
University of California San Francisco
505 Parnassus Ave, M1180B
San Francisco, CA 94143-0124
Tel: (415) 476-5706
Fax: (415) 476-3505
E-mail: [email protected]
Journal Subject Codes: [5] Arrhythmias, clinical electrophysiology, drugs
1
DOI: 10.1161/CIRCEP.114.001781
Abstract:
Background - Advanced age is the most important risk factor for atrial fibrillation (AF),
however the mechanism remains unknown. Telomeres, regions of DNA that shorten with cell
division, are considered reliable markers of biological aging. We sought to examine the
association between leukocyte telomere length (LTL) and incident AF in a large populationbased cohort using direct LTL measurements and genetic data. To further explore our findings,
we compared atrial cell telomere length (ATL) and LTL in cardiac surgery patients.
Methods and Results - Mean LTL and the TERT rs2736100 single nucleotide polymorphism
(SNP) were assessed as predictors of incident AF in the Cardiovascular Health Studyy (CHS).
(
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
Among the surgical patients, within subject comparison of ATL versuss LTL
LTL was
was aassessed.
sses
ss
esse
es
seed.
Among 1639 CHS participants, we observed no relationship between mean
incident
n LT
LTL
L an
andd in
inci
c de
ci
d AF
prior to andd after
95% CI:
aft
f er aadjustment
djus
dj
ustm
ment for potential confounders
confoundder
e s (adjusted ha
hhazard
zaard ratio [HR] 1.09; 95
0.92-1.29, p=0.299);
strongly
with
AF
same
model.
p=0
0.299); chronologic
chr
hron
hr
o olog
on
ollog
ogic
i age
ic
aggee remained
rem
emai
a nedd strong
ngly
y aassociated
ssoc
o iate
oc
tedd w
te
ith
hA
F in
n tthe
he sam
am
me m
o
No association
observed
the
TERT
SNP
(adjusted
attiion was obs
b errved bbetween
etw
wee
een th
he TE
T
RT
T rrs2736100
s273
7361100 S
NP
P and
and incident
incid
den
ent AF
A (ad
adjussteed HR:
0.95; 95% CI: 0.88-1.04,
cardiac
0.88-1.0
0.
.04,, p=0.265).
.0
p=0
=0.265).
).. In 35 cardia
i c su
ia
ssurgery
r eryy pa
rg
patients (26
(26
2 withh AF),
AF),
AF
) ATL was
),
longer than
n LTL
LT
TL (1
(1.1
(1.19
19 ± 00.20
.220 versus 11.02
.022 ± 0.25
0.225 [T/S
[T
T/S ratio],
ratio
i ], p<0.001),
p<0
0.0001
01),
), a finding
findiingg that
tha
hatt remained
remaii
re
consistent within
wit
ithi
hinn the
th
he AF subgroup.
subbgr
grou
oup.
p.
Conclusions - Our study revealed no evidence of an association between LTL and incident AF
and no evidence of relative atrial cell telomere shortening in AF. Chronological aging
independent of biological markers of aging is the primary risk factor for AF.
Key words: atrial fibrillation, aging, genetics, telomere genetics
2
DOI: 10.1161/CIRCEP.114.001781
Introduction
Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, is a growing health
epidemic associated with increased risks of heart failure, stroke, and death.1–3 The direct costs
for treating the arrhythmia in the United States alone have been estimated to be $6.65 billion
dollars annually.4 The clinical and economic burdens of AF are anticipated to grow dramatically
in the coming years secondary to its expanding prevalence.5 The devastating impact of the
arrhythmia is further exacerbated by a lack of highly effective treatment strategies, which likely
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
stems from our limited understanding of its underlying pathophysiology.
gy.6
gy
Advancing age is the most critical risk factor for the development
ent ooff AF
AF, re
refl
reflected
fleecte
fl
tedd bby its
te
ranging
angi
an
giing
ng from
fro
rom
m le
lless
ss than 0.1% among ind
individuals
div
ivid
i uals younger
youngger tha
than
h n 55 years of age to
ha
prevalence ran
77,8
,88
upwards off 10
10%
0% among ooctogenarians.
ctoggenarriaans.7,
Despite
D
esppitte the
he dra
dramatic
rama
ra
matiic im
ma
impac
impact
ct off aage
ge onn tthe
he riskk off AF,
n s responsible
nisms
resp
re
sponsiible ffor
sp
or this relationship
rellationnsh
re
ship
ip rem
ip
aiin un
uunclear.
cllea
ear. Ou
Our iinsight
nsigh
ghht in
into tthe
he bbiology
iollo
the mechanisms
remain
governing the ag
aging
ging pr
pprocess
occess also
l remains incomplete,
incompl
plete, however
pl
however str
strong
rongg ev
evid
evidence
idence hhas
id
as eemerge
emerged
merg
me
ge
9
supporting a role
oll for
f telomeres.
ttelomeres
ell
Telomeres
T
ello
are repetiti
repetitive
titi
ti
ti e DNA
DNA sequences
seq ences ([TTAGGG]
([TT
TTAG
AGGG
GG]]n)
located at the ends of chromosomes that shorten with advancing age as a result of repeated
somatic cell division.10 These chromosomal “caps” function to prevent DNA degradation,
however this ability becomes increasingly limited as telomere length shortens, resulting in
cellular senescence, apoptosis, and an increased susceptibility to oxidative stress.11
Telomere length and the rate of telomeric shortening, termed telomere attrition, varies
widely within the population and has been suggested to influence inter-individual variability in
the aging process and susceptibility to age-related diseases.12 Links have been established
between telomere length and multiple age-related cardiovascular disorders including
atherosclerosis, heart failure, and left ventricular hypertrophy.13–16 Notably, telomere length is
3
DOI: 10.1161/CIRCEP.114.001781
also highly heritable and could also potentially account for a portion of the missing heritability
within AF that remains unexplained following large scale genome wide association studies
(GWAS) dedicated to the arrhythmia.17–22 Given the critical importance of aging in AF, we
sought to investigate the impact of leukocyte telomere length (LTL) on the risk of incident AF in
a large population-based cohort using both direct LTL measurements and a single nucleotide
polymorphism (SNP) previously associated with reduced LTL. In order to determine the relative
relationship between atrial cell telomere length (ATL) and LTL, we performed additional
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
analyses among patients undergoing cardiac surgery.
Methods
a on betwee
atio
at
en LT
TL an
andd in
cide
ide
dent
ntt A
F wa
w
exam
min
ined
e in th
ed
he C
Ca
ardio
io
ovasc
scul
sc
u ar H
eaalt
lth Study
The association
between
LTL
incident
AF
wass ex
examined
the
Cardiovascular
Health
(CHS), a prospective
r sppec
rosp
ecti
t ve population-based
ti
pop
o ullat
atio
onn baase
sed
d ccohort
oho
hort
rt sstudy.
tu
udy
d .233 A cr
cros
cross-sectional
o s-ssecctiion
os
onal
al comparison
com
ompa
parriso
pa
s n of ATL
so
AT and
LTL was performed
erfor
o me
or
medd in
n a ccohort
ohor
oh
ortt of ppatients
or
atiient
at
ntss who
who underwent
unnde
d rw
wen
entt ca
ccardiac
rddia
i c su
surg
surgery
rg
ger
eryy and
an
nd left
left
f aatrial
tria
tr
iaal
appendage ex
eexcision
c si
ci
s on
o at
at S
Sutter
uttte
t r Hosp
H
Ho
Hospital,
osppitall, Sacramento,
Sacr
Sa
c am
a en
e to,
to, CA
CA..
Cardiovascular Health Study (CHS)
The CHS is a population-based cohort study designed to investigate risk factors for
cardiovascular disease in the elderly. The design, recruitment, baseline characterization, and
outcome ascertainment procedures for CHS have been previously described in detail.23,24
Briefly, a total of 5,201 participants aged 65 years and older were recruited in 1989-1990 from
Medicare eligibility lists in four US communities: Forsyth County, North Carolina; Washington
County, Maryland; Sacramento County, California; and Pittsburgh, Pennsylvania. An additional
687 participants, almost all African Americans, were recruited into the study in 1992-1993.
Written informed consent was obtained, and all procedures were conducted under institutionally
approved protocols for use of human subjects.
4
DOI: 10.1161/CIRCEP.114.001781
Examinations and Event Ascertainment
Participants underwent comprehensive examinations at study entry to document baseline
demographics and medical co-morbidities. Self-identified race was dichotomized as white and
non-white. Hypertension was defined as a reported history of physician-diagnosed hypertension
and use of antihypertensive medications, or systolic blood pressure greater than or equal to 140
mm Hg, or diastolic blood pressure greater than or equal to 90. Participants were classified as
diabetic if they used an anti-hyperglycemic medication or had a fasting glucose concentration
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
greater than or equal to 126 mg/dL. Prevalent heart failure was diagnosed
osed byy pparticipant
articipa
p nt sselfe
report and confirmed by medical record verification, while prevalent coronary
corona
nary
ry artery
arttery
ar
ery
y disease
diise
seaas was
defined as angi
angina,
gina
gi
n , pprevious
na
revi
re
v ou
ous myocardial infarction, previous
preevious coronary
corona
n ry ar
aartery
tery bypass grafting
grafting,
g or
previous angioplasty,
ng oplasty, all bby
ngi
y pparticipant
articiipant sself-report
elff-repoort an
and
nd co
confirmed
onf
nfir
irm
ir
med
d by me
m
medical
diical re
record
eco
ordd ver
verification.
riffic
bsequent
bsequ
uen
entt follow-up
follow-upp was performed
peerf
rformedd wi
with
th alt
lternaati
lt
tingg cli
ini
nic vi
isiits and
nd phone
phone calls
callls every
e
Subsequent
alternating
clinic
visits
six months untill 1999
199
9999 and
an
nd semi-annual
semi-annual
i
l phone
phhone calls th
thereafter.
hereafft
fter. Re
R
Resting
s in
st
i g 12
12-lead
dE
ECGs
CGss we
CG
w
were
re
performed att each
h cli
clinic
liniic visit.
iisit
sit
it P
Pre
Prevalent
alent
lentt AF
AF att bbaseline
eli
line was
as ddoc
documented
mented
tedd using
sing
in the
th baseline
ba li
ECG, while incident AF was ascertained on the basis of clinic visit ECGs and hospital discharge
diagnosis codes that were supplemented with Medicare inpatient and outpatient claims data 25,26.
Previous work on selected subgroups of CHS participants demonstrated that this approach to
incident AF ascertainment had positive and negative predictive values of 98.6% and 99.9%,
respectively.27,28
Cardiac Surgery Cohort
&RQVHFXWLYHFRQVHQWLQJDGXOWSDWLHQWV•\HDUVROGXQGHUJRLQJFDUGLDFVXUJHU\ZLWKOHIWDWUial
appendage excision at Sutter Hospital, Sacramento Medical Center were recruited between
October 1, 2010 and November 1, 2012. Patients were excluded if they had congenital heart
5
DOI: 10.1161/CIRCEP.114.001781
disease, any history of rheumatic valve disease or mitral stenosis, if a right thoracotomy
approach was employed, if they were unable to provide informed and witnessed signed consent,
or if they were pregnant or incarcerated. Participant demographics and medical details were
obtained using a study questionnaire and were verified with a subsequent chart review. All study
participants provided informed written consent under protocols that were approved by both the
University of California, San Francisco (UCSF) and Sutter Hospital, Sacramento, CA.
Telomere Analyses
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
Different techniques were utilized for telomere length measurements inn the different co
cohorts,
oho
hort
r
namely Southern blot analysis of terminal restriction fragment lengths in CHS
CHS and
and quantitative
q an
qu
nti
titta
ta
polymerasee chain
surgery
performed
cha
hain
ha
in rreaction
e ct
ea
c io
on (qPCR) in the cardiac su
urg
r ery cohort. Thee llaboratories
a oratories that perf
ab
f
these measurements
our
study
previously
satisfactory
reproducibility
and
urements in ou
ur stud
udy had
ud
haad pr
reviouusly
y ddocumented
occumen
ente
en
tedd sat
te
tissfacto
tory
ry
y re
eprod
odducib
ibilityy an
n
2
correlation of bboth
methods.
othh m
ot
eth
hodds.29
CHS
30,31
,31
31
Details regarding
arding
rdi
din LTL
LTL meas
measurements
rements
ts within
ithi
it
ithin
hi CHS
CHS have
hhaa e been
b
pre
previously
iio
o sll ddescribed
described.
ibed
d 30
Briefly,
Bri
B
rii
1675 participants were randomly selected for LTL analysis among a subgroup of the cohort that
had completed the 1992-93 and 1997-98 clinic examinations, had stored genetic samples
collected at these visits, and had signed consent for DNA analysis. LTL measurement was
performed on blood collected at the 1992–93 clinic visit using Southern blot analysis of terminal
restriction fragment lengths and reported in kilobases.32 Telomere measurements were
performed in duplicate, and the mean was used for statistical analyses. The Pearson’s
Correlation Coefficient for duplicates was 0.96, with an average coefficient of variation for
paired sets of 2.5%. The laboratory conducting the LTL measurements was blinded to all
characteristics of participants.
6
DOI: 10.1161/CIRCEP.114.001781
Cardiac Surgery Cohort
Lymphocyte DNA was purified from the buffy coat using the Gentra Puregene Blood Kit
(Qiagen Inc., Valencia, CA) obtained from phlebotomy performed prior to surgery.
Intraoperatively, left atrial appendage samples were immediately flash frozen in liquid nitrogen.
All samples were shipped to UCSF in dry ice, stored in a -80°C freezer, and analyses were
batched. Genomic DNA was isolated from atrial tissue using the AllPrep DNA/RNA Mini Kit
(Qiagen Inc.). Telomere length analysis for all samples was adapted from the qPCR technique
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
originally described by Cawthon.33 The qPCR reaction conditions and
d pr
pprimers
imers utilized
d for
for
o the
telomere and single copy gene (human beta-globin) have been previously
usly re
repo
reported.
p rtted
po
d.34 Th
Thee qPCR
cond
nduc
nd
uccte
t d us
sin
i g the Roche Lightcycle
er 48
4480
0 real-timee PCR
CR
R machine (Roche,
assays weree co
conducted
using
Lightcycler
Indianapolis,
is, IIN).
is
N). Telome
Telomere
mere le
lengths
engtths aree rep
reported
porteed as th
the
he T
T/S
/S
S ra
ratio,
atio
o, the ra
ratio
atioo of m
mean
eaan ttelomere
elo
ome
m r
u e ccopy
uence
opy
op
py nu
mb
ber ((T)
T to th
T)
the refe
f re
fe
rencce si
ing
ngle
l -co
copy
co
py gene
gen
en
ne copy num
umbe
um
ber (S
be
((S).
).
repeat sequence
number
reference
single-copy
number
LTL SNPss and
d CHS
CHS Genotyping
Genotyp
typ
ypiingg
In order to further
f rth
rther
the iin
investigate
n estigate
sti
tigatt th
the potential
tenti
tiall relationship
lati
ti shi
hip between
bbet
ett een L
LTL
TL and
ndd A
AF,
AF
F wee so
sought
ght
ht tto
examine for associations between single nucleotide polymorphisms (SNPs) linked to reduced
LTL and incident AF. Review of 9 SNPs previously associated with LTL through genome wide
association studies revealed a single SNP that had also been directly genotyped within the CHS
cohort using a DNA microarray.17,35 In a recent large meta-analysis of genome wide association
studies, the minor allele (C>A) was shown to be associated with reduced telomere length (beta
coefficient: -0.078, p-value = 4.38 x 10-19).17 The genotyping methodology for rs2736100 within
CHS has been previously described.22 SNP genotyping was performed using the Illumina 370
CNV DNA microarray and analyzed using the BeadStudio variant calling algorithm (Illumina,
San Diego, CA). Genetic analyses were restricted to individuals of Western European ancestry.
7
DOI: 10.1161/CIRCEP.114.001781
Statistical Analysis
Normally distributed continuous variables are presented as means + standard deviation and were
compared using the Student’s t-test. Comparison of categorical values was performed using the
Chi-squared test. In CHS, time-to-event analyses using Cox proportional hazards models were
employed to evaluate the association of LTL with incident AF. The primary predictor, LTL, was
treated as both an ordinal and a categorical variable divided into tertiles (to maintain consistency
with previous literature).13,14 Multivariable Cox regression analyses were performed to adjust for
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
potential confounding. Covariates added to these models included baseline
seline age,
age
g , sex, selfsel
ellfreported race, hypertension, diabetes, body mass index, coronary artery
disease,
y dise
seas
ase,
e aand
ndd ccongestive
onnges
ge
heart failure.
r Si
re.
S
Similar
m la
mi
larr analyses
an
nallyses restricted to a subgro
subgroup
roupp of particip
ro
participants
pantss w
within
ithin the overall cohort
coh
h
that had noo baseline
failure
ba
hyper
hypertension,
ertennsiion, diabetes,
diabeetes, coronary
corronnaryy arte
artery
tery
te
ry ddisease,
iseeasse, oorr con
congestive
ongesttiv
i e he
heartt ffai
ai
were also perf
pperformed.
forrme
med
ed. E
Examinations
xamiinati
tions fo
ti
for an iinteraction
n erracti
nt
t on between
ti
bet
etw
ween
ween
we
e age
gee andd LTL
LTL
L were
were perf
performed
formee
using baseline
l age
line
g dichotomized
dic
i ho
hoto
tomiizedd by its
to
its median
it
medi
dian value
di
vallue in
in both
botth unadjusted
unad
adju
justed
ju
ed
d andd mul
multivariate
ltiivar
aria
iatte models.
ia
m
An additivee genetic
ti model
dell was
as emplo
employed
pll ed
d ffor tthe
he genetic
eti
tic S
SNP
NP anal
analyses.
l ses Li
Linear regression
io
analysis was performed in order to examine for an association between the SNP and LTL.
Bivariate and multivariable Cox regression models, as described above, were utilized to examine
for an association between the SNP and incident AF. For the adjusted survival curves,
categorical covariates were set at 0 and continuous covariates were set at their mean values. For
the surgical cohort, ATL and LTL were compared using mixed effects regression models
adjusting for age and gender. Assessment for association and correlation between ATL and LTL
was performed using linear regression adjusting for the same covariates and the Pearson pairwise
correlation coefficient, respectively. Two-tailed p-values < 0.05 were considered statistically
significant. Statistical analyses were performed using Stata version 12 (College Station, TX).
8
DOI: 10.1161/CIRCEP.114.001781
Results
CHS Participant Characteristics
A total of 1675 individuals from the CHS cohort underwent LTL measurement. Among this
group, 36 had prevalent AF and were excluded from the analysis. At baseline, the mean age of
the cohort was 72.2 years, 41.3% were male, and 71.3% were classified as white. The remaining
baseline clinical characteristics of the cohort, stratified by the presence or absence of incident
AF, are summarized in Table 1. During a mean follow-up period of 11.6 years, a total of 476 of
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
the 1639 individuals were diagnosed with incident AF.
LTL and the Risk of Incident AF in CHS
Mean LTL w
with a
within
ithi
it
hinn the
hi
the cohort
co
oho
h rt was 6.33 kb. Each decade
deecade of advanc
advancing
cingg aage
ge was associated w
significant 21%
LTL
Bivariate
treating
LTL
21% lower mean
meaan L
TL ((p<0.001).
p<0.00011).. B
ivvariiatte an
aanalysis
nal
alys
al
ysis tr
reatingg LT
L
L ass a ccontinuous
ontinu
nuo
nu
variable revealed
vealed
veale
l d noo statistically
le
stati
tistic
ti allly significant
sig
gni
n fi
ficantt association
assoc
o iati
tion between
ti
bet
etwe
weeen llonger
we
onge
on
ger ttelomere
elome
mere llength
me
ength
th and
incident AF
ratio
[HR]
each
LTL,
CI:
F (hazard
(hhazardd rati
tioo [H
ti
HR] 00.91
.991 for
for ea
ch
h kilobase
kil
i obbase increase
i crease iin
in
n LT
L
L 995%
L,
5 C
5%
I: 00.78-1.06,
.7788 1.
1 06,
p=0.226). Following
statistically
significant
Follo
F
oll
llo ing
i adjustment
adj
dj stment
tm t for
fo pre-specified
pre specified
ifiiedd covariates,
if
co ariates
riiatt again
aii no statisticall
tati
tisti
ticall
ll significa
ignifi
ifi
relationship between telomere length and AF was observed, with a HR close to 1 (HR 1.09 for
each kilobase increase in LTL, 95% CI: 0.92-1.29, p=0.299). Similar results were obtained when
the analysis was restricted to 705 individuals with no baseline risk factors for AF including
hypertension, diabetes, coronary artery disease, and congestive heart failure (unadjusted HR:
0.95, 95% CI: 0.74-1.22, p =0.684; adjusted HR: 1.12, 95% CI: 0.87-1.45, p=0.378).
The results examining LTL in tertiles as an ordinal and a categorical variable are
presented in Figures 1 and 2, respectively. No significant associations were observed. Of note,
in each multivariable model, age remained a statistically significant predictor of incident AF
following adjustment for LTL. Examination for an impact of age on the association of LTL with
9
DOI: 10.1161/CIRCEP.114.001781
incident AF revealed no evidence of an interaction in both unadjusted (p=0.522) and adjusted
(p=0.765) models when dichotomizing age based on the median value of 72 years. Consistent
with these results, the HRs for incident AF among individuals less than 72 years (unadjusted HR:
0.96 [95% CI: 0.77-1.20; p = 0.719], adjusted HR: 1.09 [95% CI: 0.86-1.38; p = 0.484]) were
nearly identical to those among individuals older than 72 years (unadjusted HR: 0.96 [95% CI:
0.77-1.19; p = 0.699], adjusted HR: 1.09 [95% CI: 0.86 - 1.39; p = 0.475]).
LTL associated SNP and the Risk of Incident AF in CHS
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
A total of 3794 individuals of Western European ancestry underwent successful SNP ge
genotyping
eno
not
of rs2736100. Within this subgroup, 1235 had also undergone LTL measurement.
Linear
measuure
reme
mentt. L
inea
in
earr
ea
regression analysis
rs2736100
ana
naaly
lysi
siis using
u in
us
i g an
an additive genetic model
modeel confirmed
co
onfirmed an association
assoc
ociation between rs27
oc
and LTL (ȕ-coefficient:
ȕ-co
ȕoefficient: -0
-0.065
-0.065,
65, 95
65
95%
5% CI
CI:
I: -0
-0.111
0.1111 - -0.
-0.018,
.018,
8 pp=0.006).
=0..0006).
=0
06 Co
Cons
Consistent
sis
istentt w
with
ithh previous
prev
evioo
ev
work, our find
ffindings
din
ngs aalso
lso de
ddemonstrated
monsttrated
ed tthat
hat th
the
he mi
minor
i
allele
al
lle
l le was
as ass
associated
sssoc
o ia
i tedd wi
with
th
h a red
reduced
duced
dL
LTL.
Among thee 3794
37794 individuals
inddivid
iduuals that
id
thhat had
had undergone
unde
d rg
gone successful
successful
f genotyping,
genot
otyp
y in
yp
i g, Cox
Cox regression
reg
gresssio
on analysis
ana
revealed no
AF
HR: 00.96
o association
ciiati
tio bet
bbetween
ett een th
the SN
SNP
P and
d incident
incid
identt A
F ((unadjusted
nadj
dj sted
tedd HR
96 [[95%
95%
95
% CI
CI: 00.89.104, p = 0.338], adjusted HR: 0.95 [95% CI: 0.88-1.04, p=0.265]) (Figure 3).
Cardiac Surgery Cohort Participant Characteristics
A total of 35 patients undergoing cardiac surgery with left atrial appendage excision at Sutter
Hospital, Sacramento provided both atrial tissue and peripheral blood for telomere length
analysis. Within this cohort, 74% of individuals had a history of AF and 60% were undergoing
cardiac surgery for a minimally invasive AF ablation. The remaining baseline characteristics are
summarized in Table 2.
Atrial Cell Telomere Length and Leukocyte Telomere Length
Among the surgical cohort of patients, the mean atrial cell telomere T/S ratio was 1.19 + 0.20 in
10
DOI: 10.1161/CIRCEP.114.001781
comparison with a mean leukocyte telomere T/S ratio of 1.02 + 0.24 (Figure 4). Mixed effects
regression modeling adjusting for age and gender revealed that ATL was significantly longer
than LTL (ȕ-coefficient 0.17, 95% CI: 0.09-0.25, p<0.001). In the multivariate model, neither
DJHȕ-coefficient -0.001, 95% CI: -0.006-S QRUJHQGHUȕ-coefficient -0.012, 95%
CI: -0.15-0.122, p=0.862) exhibited statistically significant associations with telomere length.
Multivariate linear regression analysis revealed a statistically significant association between
$7/DQG/7/ȕ-coefficient 0.30, 95% CI: 0.03-0.57, p=0.030), while their calculated pairwise
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
correlation coefficient (R2) was 0.37. Within the subgroup of patients with AF,, the mean
meaan atrial
a
cell telomere T/S ratio (1.19 + 0.21) was again longer than LTL (1.03 + 0.25)
0.25
25)) after
25
affte
aft
ter adju
ad
adjusting
djust
ju
ust
stiin
in for
age and gender
nder ((p=0.001).
nd
p=0.
p=
0 00
0.
0 1)
1). Similar results were also
so observed
observed forr the 9 patients without AF
F (1.21
+ 0.16 in the
he atria
he
atria versuss 11.00
.000 + 0.
0.25
.2255 in leukocytes;
leuk
ukocyytees; adjusted
ad
dju
ust
sted
ed
d p=0.08).
p=0
0.008).
Discussion
n
igation
ig
gat
atio
on involving
invo
in
volv
l in
lv
ingg 1639
1639 elderly
eld
der
e ly
ly subjects
subbjjeectts from
from
fr
o a ppopulation-based
opul
op
ullattio
ion-ba
b se
ba
sedd co
coho
cohort
h rtt sstudy
ho
tudy
tu
dy
Our investigation
identified no association between LTL and the risk of incident AF. Further strengthening this
finding, we also found no association between rs2736100, a SNP associated with reduced LTL,
and incident AF among 3794 individuals from the same cohort. In an effort to advance our
insights into atrial biology with respect to telomere length, we compared ATL and LTL among
patients with and without AF undergoing cardiac surgery. ATL was longer than LTL in both the
overall group and among the subgroup of patients with AF. Because ATL correlated with LTL,
it appears unlikely that ATL alone is important in the development of AF. Collectively, these
findings suggest that telomere shortening does not account for the increased risk of AF
associated with aging.
The importance of advancing age in the pathogenesis of AF is highlighted by its
11
DOI: 10.1161/CIRCEP.114.001781
dramatically increased prevalence within older populations. Although extremely rare among
individuals less than 50 years of age, the arrhythmia affects upwards of 10% of octo- and
nonagenerians.7 This age-dependent increase in its frequency, in association with our aging
population, is leading to a surge in its overall prevalence. Indeed, a recent study projected that
the number of affected Americans may grow nearly 8-fold from approximately 2.3 million in the
year 2000 to nearly 16 million by 2050.5 This worrisome forecast, further aggravated by our
lack of preventive strategies and definitive therapies for the arrhythmia, emphasizes the need for
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
an improved understanding into the pathophysiology of the arrhythmia.
a. Insig
Insight
ght into thee
pathophysiological mechanisms through which age predisposes to the arrhythmia
arrhhytthm
hmia
i has
ia
has tthe
he
potential to
therapeutic
o uunveil
nvei
nv
eill cr
ei
crit
critical
itical
it
all biological pathways thatt co
ccould
uld serve ass targe
targets
gets for novel therapeu
ge
interventions.
ns.
Telomeres,
omeres,
omere
ress, rrepetitive
re
ep
pettit
itiive DNA
DN el
elem
elements
ementss llocated
em
ocated
oc
d att th
the
he ends
en
nds ooff ch
chromosomes,
hromosoomes, hhave
ave bbeen
een
implicated as po
ppotential
tentiial me
m
mediators
diators off bbiological
di
iologi
gicall ag
gi
aging.
ging.
g 10 Co
Consistent
C
nsiiste
t nt with
wit
ithh this
it
th
his hypothesis,
hyp
ypotthe
hesi
s s, reduced
si
redd
telomere length
ength
gth
th has
ha bbeen
e associated
iattedd with
iith
th an iincreased
n
d ri
risk
iskk ffor multiple
m lltiple
tipll age-dependent
agee ddependent
dentt
cardiovascular conditions. Telomere shortening is felt to contribute to biological aging through
an increased vulnerability to oxidative stress and subsequent fibrosis secondary to reduced
genomic stability.12 Notably, atrial fibrosis is considered critical for the initiation and
maintenance of AF through its role as a substrate that promotes regional conduction velocity
heterogeneity.36,37 Despite this apparent overlapping pathophysiology, we identified no evidence
of an association between LTL and the risk of incident AF among CHS participants. Given the
large size of our study and the persistence of statistically significant relationships between
known risk factors (such as age) and AF despite adjustment for LTL, we have provided strong
evidence suggesting the absence of an independent clinically significant impact of LTL on the
12
DOI: 10.1161/CIRCEP.114.001781
risk of AF.
In an effort to further explore for a potential link between LTL and AF, we examined for
an association between a SNP associated with reduced LTL and the arrhythmia. The rs2736100
SNP lies in the vicinity of the TERT gene which encodes for the enzyme telomerase reverse
transcriptase. Telomerase reverse transcriptase functions to elongate telomeres following
cellular division in an effort to preserve telomere length over time. For this analysis, the TERT
SNP effectively functions as an instrumental variable in the relationship between LTL and AF,
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
thus serving to minimize the potential impact of confounding variabless on the analysis.
The
analys
y is. T
h lack
of association between the SNP and incident AF further reinforces ourr init
initial
LTL
tia
i l findings
find
ndin
dings
g tthat
hatt L
ha
does not influence
risk
population.
n uen
nflu
ence
ce tthe
he ris
sk of the AF in this popula
ati
tion.
Following
lowing
lo
owing these rresults,
esults
ts, furt
further
rthher ex
rt
eexploration
ploooration
rattio
on iinto
ntto tthe
h rrelationship
he
ellatio
ionshhipp be
io
between
etweeen telo
telomere
lomeeree llength
and atrial biology
through
LTL
cohort
gy was
gy
was performed
perfformed
d thr
h ou
hr
ough comparison
com
ompa
om
parison off ATL
pa
ATL and
nd L
TL iinn a separate
seepa
paratte coh
cohor
hor of
individualss that had
had
d undergone
und
nder
nd
e go
g ne left
left
f atrial
attriial appendage
app
ppenddage
pp
g excisi
excision
ion during
d ri
du
ring
n cardiac
ng
car
arrdi
diac surgery.
surge
g ry.
ry
y ATL
ATL was
noted to bee longer
than
individuals
lo
tha LTL
LTL among the
th entire
ti cohort
ohh t and
d within
iithin
thiin the
th
the subgroup
s bbgro p off iindi
ndi
di id all with
AF. Because ATL correlated with LTL, extrapolation of these observations in combination with
the LTL findings above argues against an important telomere length phenomenon localized to
the atria. This relative preservation of ATL may potentially account for the apparent lack of
impact of telomere length on the risk of AF.
Of note, a longer telomere length within atrial cells relative to leukocytes is consistent
with our understanding of both atrial biology and the mechanism of telomere attrition. Telomere
length shortens progressively with age secondary to an inability of the telomerase enzyme to
fully replicate telomeres following repeated somatic cell division.38 Atrial tissue samples are
composed of a combination of cell types including myocytes, fibroblasts, endothelial and
13
DOI: 10.1161/CIRCEP.114.001781
vascular smooth muscles cells. Notably, atrial and ventricular myocytes undergo very limited
cell division following embryogenesis, which may potentially protect them from the adverse
consequences of telomere shortening.39,40 To our knowledge, our study is the first to document
that telomere length is longer in atrial tissue relative to leukocytes.
Our findings suggest that aging increases the risk of AF through biological pathways that
are independent of LTL or through a mechanism restricted to chronological aging. Examining
for a potential role of telomere biology in the pathogenesis of AF was particularly important
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
given the critical, yet largely unexplained impact of advancing age on the risk of the arrhythmia.
arrrhy
hyth
t
Future work can now focus on other biological pathways associated with aaging
ging
gi
ing that
that
hat may
may
th
he development
deeve
v lopm
pment of AF. As telomeree le
pm
llength
ngth is gene
generally
era
r llyy considered
considered the prima
predispose to the
primary
marker of bi
bbiological
iollogical aging,
aging
ng, our
ouur results
resu
sults may
su
m y also
ma
alsoo suggest
sugggeest that
tha
hatt tthere
herre is something
somet
ethingg specific
spe
peccificc ttoo
cal, rrather
athe
at
hee th
her
han bbiological,
i logicall, aage
io
ge tha
hatt is
ha
is inherently
inhherentl
tlyy im
tl
mport
rtan
rt
a t. As
an
As a hy
hypo
poth
hetic
ti all
chronological,
than
that
important.
hypothetical
erha
h ps
p the
there
h re iiss a cumula
l tively
i ly growing
growiingg pprobability
roba
b bi
bili
ili
l ty off AF
A iinduction
ndductiion as mo
ore
r aand
nd more
example, pperhaps
cumulatively
more
premature at
atrial
triiall contractions
tr ti
(k
(known
(kno n tto be
be an iimportant
m rtt t AF risk
iskk factor)
factt ) are iintrod
introduced
nttrodd ced
ed
d att
different times into the atrial substrate.41 An improved understanding of the mechanisms
governing the relationship between advanced age and the risk of AF will likely be critical for the
development of preventive and therapeutic treatment modalities necessary to combat this
growing health epidemic.
Our study has several limitations. Because our population-based analysis was restricted
WRLQGLYLGXDOV•\HDUVRIDJHLWGRHVQRWUXOHRXWDQLPSDFWRI/7/LQ\RXQJHUDJHJURXps.
Although this may limit the generalizability of our findings, we would highlight that the vast
majority of individuals affected by AF are elderly, emphasizing the importance of furthering our
understanding of the arrhythmia within this subgroup of the population. Second, it is
14
DOI: 10.1161/CIRCEP.114.001781
conceivable that our study was inadequately powered to detect an association between LTL and
AF. It should be noted that we failed to detect an association between hypertension and AF in
our multivariate model (HR: 1.10, 95% CI: 0.90-1.35, p=0.342), though an association was
observed on unadjusted analysis (HR: 1.19, 95% CI: 1.07-1.32, p=0.001). The magnitude of
association between hypertension and AF in our study was comparable to previous work
involving the CHS cohort and the association on multivariate analysis would likely have been
statistically significant had our cohort had been larger. Despite these observations, we feel that it
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
is unlikely that inadequate power was responsible for our lack of association
LTL
ciation between LT
TL and
AF given that the direction of association identified was opposite the expectation
expeccta
t tion
tiion that
that
hat older
olde
ol
der
de
biological age
AF
rs2736100
agee increased
inc
n reeas
a ed
e A
F risk. Third, the rs2736
610
100 SNP is a modest
m de
mo
d st predictor of LTL
variability aand
genetic
association
nd should not
noot be viewed
viiew
wed
d as ddefinitive
efinnitive
vee gen
enetic
icc evidence
evidennce
nc to ru
rule
ulee oout
ut aan
n ass
associatio
ssociaatio
between LTL
between
TL an
and
nd th
the risk
riiskk off AF.
AF Fourth,
Fou
ourt
rth,
rt
t wee cannot
cannnott rulee out
ca
out a potential
poote
tenttiall association
assooci
ciation betwee
betwee the
rate of telomere
mere attrition
attriitiionn and
andd AF
AF given
gi
that
th
hatt telomere
telomere
l
length
lenggth
h was only
onl
n y measured
me
d at a single
sing
si
nggle ttime
point. Finally,
than
all
ll although
altho
lthho gh
lt
h ATL
ATL was
as clearly
cl
clearl
l rll and
d consistently
consistentl
isttentl
tl longer
l
th LTL,
L
LTL
TL wee were
ere nott
adequately powered to examine for an association between ATL (alone) and the risk of AF in our
relatively small surgical cohort. Although the correlation between ATL and LTL would support
the notion that ATL is unlikely to be critical to AF development, the modest R2 value of 0.37
suggests we cannot exclude the possibility that ATL might yet be important in AF.
Our study has several limitations. Because our population-based analysis was restricted
to indivLGXDOV•\HDUVRIDJHLWGRHVQRWUXOHRXWDQLPSDFWRI/7/LQ\RXQJHUDJHJURXSV
Although this may limit the generalizability of our findings, we would highlight that the vast
majority of individuals affected by AF are elderly, emphasizing the importance of furthering our
understanding of the arrhythmia within this subgroup of the population. Second, it is
15
DOI: 10.1161/CIRCEP.114.001781
conceivable that our study was inadequately powered to detect an association between LTL and
AF. It should be noted that we failed to detect an association between hypertension and AF in
our multivariate model (HR: 1.10, 95% CI: 0.90-1.35, p=0.342), though an association was
observed on unadjusted analysis (HR: 1.19, 95% CI: 1.07-1.32, p=0.001). The magnitude of
association between hypertension and AF in our study was comparable to previous work
involving the CHS cohort and the association on multivariate analysis would likely have been
statistically significant had our cohort had been larger. Given that the point estimate for LTL as
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
a predictor of AF was in the opposite direction of what would be expected
biological
cted if older biolo
ogi
gicc age
increased AF risk, we feel it is unlikely that inadequate power was responsible
negative
ponsi
siibl
blee for
f r ou
fo
ourr ne
neg
ga
findings. Third,
association
between
the
attrition
Thir
ird,
ir
d, we
d,
we cannot
cannnot rule out a potential asso
ca
ociiation betwee
en th
he rate of telomere attr
and AF given
telomere
length
measured
although
ven that telome
ven
ere len
engthh was
was on
oonly
ly
y me
eassureed att a ssingle
iinnglee ttime
imee point.
poiint. Finally,
Fiinaallly, al
lthhouu
ATL was clearl
consistently
longer
than
LTL,
were
adequately
examine
cclearly
ly an
and
nd consi
istently
tl lon
onnger
ge th
han
nL
TL, we w
TL
ere nnot
er
ot ad
adeq
equattely
y po
poweredd to
t exa
a
for an association
small
ciation
ciati
ion between
betweeen
e ATL
ATL (alone)
(allone)
e) aand
ndd the
h riskk off A
AF
F in
i our relatively
rellativ
iv
velly smal
ll surgical
suurg
rgic
iccal ccohort.
Although the
ATL
LTL
that
ATL
hhee correlation
lati
ti bbetween
bet
ett een A
TL and
ndd L
TL would
o ld support
s pport
rtt tthe
he notion
oti
tio th
att A
TL iis unlikely
nlik
likk
li
to be critical to AF development, the modest R2 value of 0.37 suggests we cannot exclude the
possibility that ATL might yet be important in AF.
Conclusions
Our study found no evidence that LTL influences the risk of incident AF. ATL was noted to be
longer than LTL among subjects with and without AF undergoing cardiac surgery. Reduced
telomere attrition secondary to limited somatic cell division among atrial myocytes may account
for the lack of association between LTL and the risk of AF. Our findings suggest that other
factors associated with biological aging or properties inherent to chronological aging
16
DOI: 10.1161/CIRCEP.114.001781
independent of cell division or telomere shortening are responsible for the association between
advancing age and the risk of AF.
Funding Sources: This work was made possible by an American Heart Association National
Innovative Research Grant (G.M.M) and the Joseph Drown Foundation (G.M.M.). J.D.R. is
supported by a Research Fellowship Grant from the Heart & Stroke Foundation of Canada.
Grants for the Cardiovascular Health Study include: R01 HL80698-01, NHLBI contracts
HHSN268201200036C, HHSN268200800007C, N01 HC55222, N01HC85079, N01HC85080,
N01HC85081, N01HC85082, N01HC85083, N01HC85086, and grants HL080295 and
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
HL102214, with additional contribution from the National Institute of Neurological
Neur
Ne
urol
ur
olog
ol
ogic
og
ical
ic
al D
Disorders
isor
is
ordd
or
and Stroke (NINDS). Additional support was provided by AG023629 from
m tthe
he N
he
National
attiona
onall In
Ins
Institute
on Aging (NIA).
NIA).
) A fu
).
full li
list of principal CHS investigators
investi
tiga
ig tors and institu
institutions
uttiions can be found at CHSNHLBI.org.
g.
g.
Conflict off Interest
Inte
teere
rest
st Dis
Disclosures:
i closures:
l
None.
Noone.
ne
References:
s
s:
1. Wang TJ, Larson MG, Levy D, Vasan RS, Leip EP, Wolf PA, D'Agostino RB, Murabito JM,
Kannel WB, Benjamin EJ. Temporal relations of atrial fibrillation and congestive heart failure
and their joint influence on mortality: the Framingham Heart Study. Circulation.
2003;107:2920–2925.
2. Wolf PA, Abbott RD, Kannel WB. Atrial fibrillation as an independent risk factor for stroke:
the Framingham Study. Stroke. 1991;22:983–988.
3. Benjamin EJ, Wolf PA, D’Agostino RB, Silbershatz H, Kannel WB, Levy D. Impact of atrial
fibrillation on the risk of death: the Framingham Heart Study. Circulation. 1998;98:946–952.
4. Coyne KS, Paramore C, Grandy S, Mercader M, Reynolds M, Zimetbaum P. Assessing the
direct costs of treating nonvalvular atrial fibrillation in the United States. Value Health.
2006;9:348–356.
5. Miyasaka Y, Barnes ME, Gersh BJ, Cha SS, Bailey KR, Abhayaratna WP, Seward JB, Tsang
TS. Secular trends in incidence of atrial fibrillation in Olmsted County, Minnesota, 1980 to 2000,
and implications on the projections for future prevalence. Circulation. 2006;114:119–125.
17
DOI: 10.1161/CIRCEP.114.001781
6. Nattel S. New ideas about atrial fibrillation 50 years on. Nature. 2002;415:219–226.
7. Go AS, Hylek EM, Phillips KA, Chang Y, Henault LE, Selby JV, Singer DE. Prevalence of
diagnosed atrial fibrillation in adults: national implications for rhythm management and stroke
prevention: the AnTicoagulation and Risk Factors in Atrial Fibrillation (ATRIA) Study. JAMA.
2001;285:2370–2375.
8. Lloyd-Jones DM, Wang TJ, Leip EP, Larson MG, Levy D, Vasan RS, D'Agostino RB,
Massaro JM, Beiser A, Wolf PA, Benjamin EJ. Lifetime risk for development of atrial
fibrillation: the Framingham Heart Study. Circulation. 2004;110:1042–1046.
9. Blackburn EH. Structure and function of telomeres. Nature. 1991;350:569–573.
10. Blackburn EH. Switching and signaling at the telomere. Cell. 2001;106:661–673.
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
11. O’Sullivan RJ, Karlseder J. Telomeres: protecting chromosomes against
gai
ains
nstt genome
ns
geno
ge
nome
no
me iinstability.
nssta
t b
Nat Rev Mol Cell Biol. 2010;11:171–181.
12. Blasco M
MA.
Telomeres
beyond.
A. T
ellom
o erres and human disease: ageing,
agei
eing
ei
ng, cancer andd bey
ey
yond. Nat Rev Genet.
2005;6:611–622.
1–6
1–6
–6222.
13. Brouilette
Thompson
CJ,
e te SW,
ette
SW, Moore
Moorre JS, McMahon
Mo
McMa
Mahonn AD
Ma
AD, Th
Thom
mpsonn JR,
JR, Ford
Forrd I,, Shepherd
Sheph
p er
ph
e d J,
J Packard
Pac
ackard
rd C
Samani NJ;
Scotland
Prevention
Study
risk
J; West
Wes
estt of Scotl
tlandd Coronary
tl
Corona
naary Preve
vent
ve
ntiio
nt
ion St
uddy Group.
Grou
Gr
oup. Telomere
ou
Telo
Te
l mere llength,
engt
en
g h,
h ri
iskk off
coronary heart
Study: a
eartt disease,
dissea
ease
se,, and
se
an
nd statin
sttat
atin
in treatment
tre
reat
a meent
at
n in
in the
tthhe We
W
West
st ooff Sc
Scot
Scotland
otla
ot
land
la
nd P
Primary
rima
ri
mary
ma
r P
ry
Prevention
reve
re
veent
n io
ionn Stu
nested case-control
study.
2007;369:107–114.
e
e-control
study
dyy. Lancet.
L ncet. 20
La
007;3
369
69:1
107
0 –1114
14.
14. Samanii N
NJ,
Boultby
R, Butler
R, Thompson
JR,
Telomere
shortening
NJ
J Bo
B
ltb
ltb R
B tler
tl R
Th
JR
JR Goodall
G dall
ll AH.
A
AH
H T
ell
sh
h tenii iin
atherosclerosis. Lancet. 2001;358:472–473.
15. Van der Harst P, van der Steege G, de Boer RA, Voors AA, Hall AS, Mulder MJ, van Gilst
WH, van Veldhuisen DJ; MERIT-HF Study Group. Telomere length of circulating leukocytes is
decreased in patients with chronic heart failure. J Am Coll Cardiol. 2007;49:1459–1464.
16. Vasan RS, Demissie S, Kimura M, Cupples LA, White C, Gardner JP, Cao X, Levy D,
Benjamin EJ, Aviv A. Association of leukocyte telomere length with echocardiographic left
ventricular mass: the Framingham heart study. Circulation. 2009;120:1195–1202.
17. Codd V, Nelson CP, Albrecht E, Mangino M, Deelen J, Buxton JL, Hottenga JJ, Fischer K,
Esko T, Surakka I, Broer L, Nyholt DR, Mateo Leach I, Salo P, Hägg S, Matthews MK, Palmen
J, Norata GD, O'Reilly PF, Saleheen D, Amin N, Balmforth AJ, Beekman M, de Boer RA,
Böhringer S, Braund PS, Burton PR, de Craen AJ, Denniff M, Dong Y, Douroudis K, Dubinina
E, Eriksson JG, Garlaschelli K, Guo D, Hartikainen AL, Henders AK, Houwing-Duistermaat JJ,
Kananen L, Karssen LC, Kettunen J, Klopp N, Lagou V, van Leeuwen EM, Madden PA, Mägi
R, Magnusson PK, Männistö S, McCarthy MI, Medland SE, Mihailov E, Montgomery GW,
Oostra BA, Palotie A, Peters A, Pollard H, Pouta A, Prokopenko I, Ripatti S, Salomaa V,
Suchiman HE, Valdes AM, Verweij N, Viñuela A, Wang X, Wichmann HE, Widen E,
18
DOI: 10.1161/CIRCEP.114.001781
Willemsen G, Wright MJ, Xia K, Xiao X, van Veldhuisen DJ, Catapano AL, Tobin MD, Hall
AS, Blakemore AI, van Gilst WH, Zhu H, Consortium C, Erdmann J, Reilly MP, Kathiresan S,
Schunkert H, Talmud PJ, Pedersen NL, Perola M, Ouwehand W, Kaprio J, Martin NG, van
Duijn CM, Hovatta I, Gieger C, Metspalu A, Boomsma DI, Jarvelin MR, Slagboom PE,
Thompson JR, Spector TD, van der Harst P, Samani NJ. Identification of seven loci affecting
mean telomere length and their association with disease. Nat Genet. 2013;45:422–427.
18. Gudbjartsson DF, Arnar DO, Helgadottir A, Gretarsdottir S, Holm H, Sigurdsson A,
Jonasdottir A, Baker A, Thorleifsson G, Kristjansson K, Palsson A, Blondal T, Sulem P,
Backman VM, Hardarson GA, Palsdottir E, Helgason A, Sigurjonsdottir R, Sverrisson JT,
Kostulas K, Ng MC, Baum L, So WY, Wong KS, Chan JC, Furie KL, Greenberg SM, Sale M,
Kelly P, MacRae CA, Smith EE, Rosand J, Hillert J, Ma RC, Ellinor PT, Thorgeirsson G,
Gulcher JR, Kong A, Thorsteinsdottir U, Stefansson K. Variants conferring risk of atrial
fibrillation on chromosome 4q25. Nature. 2007;448:353–357.
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
19. Gudbjartsson DF, Holm H, Gretarsdottir S, Thorleifsson G, Walters
GB,
G,
rs G
B, Thorgeirsson
Tho
horg
rgei
rg
eirrs
ei
rssoon G
rsso
Gulcher J, Mathiesen EB, Njølstad I, Nyrnes A, Wilsgaard T, Hald EM,
K,, Stol
Stoltenberg
M, Hveem
Hve
veem
em K
S
tollte
tennb
nb
C, Kucera G, Stubblefield T, Carter S, Roden D, Ng MC, Baum L, So WY,
WY Wong
Wong KS,
KS Chan
Cha JC,
Gieger C, Wichmann
HE,
Wichma
Wi
ch
hmann
n H
E, Gschwendtner A, Dichgans
Dichggan
anss M, Kuhlenbäumer
Kuhlenb
nbbäu
ume
m r G, Berger K,
Ringelsteinn EB,
Hillert
EB Bevan
Bevaan S, Markus
Mar
arku
ar
kuss HS,
ku
HS
S, Kostulas
K st
Ko
stul
u as K,
K, Hi
Hiller
rt J,
J, Sveinbjörnsdóttir
Svein
veein
inbj
björ
bj
örrn dóótt
örns
ttir
irr S,
S, Valdimarsson
Valdimars
Vaald
ldim
im
mars
EM, Løchen
DO,
Thorsteinsdottir
U,, St
Stefansson
K. A
en
n ML,
ML, Ma RC,
RC
C, Darbar
Daarbbar D,
D, Kong
Ko g A,
A, Arnar
Arrnarr DO
O, Th
horstteiinsddottirr U
tef
efan
nssonn K
sequence var
ZFHX3
16q22
with
and
stroke.
vvariant
riant
iaan in ZF
FHX
HX3 on
on 16q
q22 associates
assso
s ciiatees wit
th atrial
attri
r al ffibrillation
ib
brill
llaationn an
nd is
iischemic
ch
hem
emiic strok
okee Nat
ok
Genet. 2009;41:876–878.
9;41:
1::87
8766–8778.
8
20. Benjamin
min EJ,
EJ,
J Rice
Rice KM,
KM Arking
Arki
kingg DE,
ki
DE, Pfeufer
Pfeuffer A,
A, van Noord
N ordd C
No
C,, S
Smith
miith
h AV,
AV, S
Schnabel
ch
hnaabe
bell RB,
RB, Bis
JC, Boerwinkle
inkle E, Sinn
Si
Sinner
inn
nner
er M
MF,
F, D
F,
Dehghan
ehgh
eh
ghan A
ghan
A,, Lu
Lubi
Lubitz
b tz
bi
t S
SA,
A, D
A,
D'Agostino
'A
'Ago
Ago
gost
s in
st
inoo RB S
Sr,
r,, L
Lumley
um
mle
leyy T, Ehret GB,
Heeringa J, A
Aspelund
T, N
Newton-Cheh
C, L
Larson MG,
KD, Soliman
EZ,
Aspel
s l ndd T
Ne
e tton C
Cheh
hehh C
MG Marciante
Ma iantt KD
Soli
li
EZ Rivadeneira
Ri ade
de
F, Wang TJ, Eiríksdottir G, Levy D, Psaty BM, Li M, Chamberlain AM, Hofman A, Vasan RS,
Harris TB, Rotter JI, Kao WH, Agarwal SK, Stricker BH, Wang K, Launer LJ, Smith NL,
Chakravarti A, Uitterlinden AG, Wolf PA, Sotoodehnia N, Köttgen A, van Duijn CM, Meitinger
T, Mueller M, Perz S, Steinbeck G, Wichmann HE, Lunetta KL, Heckbert SR, Gudnason V,
Alonso A, Kääb S, Ellinor PT, Witteman JC. Variants in ZFHX3 are associated with atrial
fibrillation in individuals of European ancestry. Nat Genet. 2009;41:879–881.
21. Ellinor PT, Lunetta KL, Glazer NL, Pfeufer A, Alonso A, Chung MK, Sinner MF, de Bakker
PI, Mueller M, Lubitz SA, Fox E, Darbar D, Smith NL, Smith JD, Schnabel RB, Soliman EZ,
Rice KM, Van Wagoner DR, Beckmann BM, van Noord C, Wang K, Ehret GB, Rotter JI, Hazen
SL, Steinbeck G, Smith AV, Launer LJ, Harris TB, Makino S, Nelis M, Milan DJ, Perz S, Esko
T, Köttgen A, Moebus S, Newton-Cheh C, Li M, Möhlenkamp S, Wang TJ, Kao WH, Vasan RS,
Nöthen MM, MacRae CA, Stricker BH, Hofman A, Uitterlinden AG, Levy D, Boerwinkle E,
Metspalu A, Topol EJ, Chakravarti A, Gudnason V, Psaty BM, Roden DM, Meitinger T,
Wichmann HE, Witteman JC, Barnard J, Arking DE, Benjamin EJ, Heckbert SR, Kääb S.
Common variants in KCNN3 are associated with lone atrial fibrillation. Nat Genet.
2010;42:240–244.
19
DOI: 10.1161/CIRCEP.114.001781
22. Ellinor PT, Lunetta KL, Albert CM, Glazer NL, Ritchie MD, Smith AV, Arking DE, MüllerNurasyid M, Krijthe BP, Lubitz SA, Bis JC, Chung MK, Dörr M, Ozaki K, Roberts JD, Smith
JG, Pfeufer A, Sinner MF, Lohman K, Ding J, Smith NL, Smith JD, Rienstra M, Rice KM, Van
Wagoner DR, Magnani JW, Wakili R, Clauss S, Rotter JI, Steinbeck G, Launer LJ, Davies RW,
Borkovich M, Harris TB, Lin H, Völker U, Völzke H, Milan DJ, Hofman A, Boerwinkle E, Chen
LY, Soliman EZ, Voight BF, Li G, Chakravarti A, Kubo M, Tedrow UB, Rose LM, Ridker PM,
Conen D, Tsunoda T, Furukawa T, Sotoodehnia N, Xu S, Kamatani N, Levy D, Nakamura Y,
Parvez B, Mahida S, Furie KL, Rosand J, Muhammad R, Psaty BM, Meitinger T, Perz S,
Wichmann HE, Witteman JC, Kao WH, Kathiresan S, Roden DM, Uitterlinden AG, Rivadeneira
F, McKnight B, Sjögren M, Newman AB, Liu Y, Gollob MH, Melander O, Tanaka T, Stricker
BH, Felix SB, Alonso A, Darbar D, Barnard J, Chasman DI, Heckbert SR, Benjamin EJ,
Gudnason V, Kääb S. Meta-analysis identifies six new susceptibility loci for atrial fibrillation.
Nat Genet. 2012;44:670–675.
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
23. Fried LP, Borhani NO, Enright P, Furberg CD, Gardin JM, Kronmal
LH,
mal RA, Kuller LH
H,
Manolio TA, Mittelmark MB, Newman A, et al. The Cardiovascular He
Health
Study:
Heal
alth
al
th S
tudy
tu
dy:: design
dy
desi
de
siign
g and
a
rationale. Ann Epidemiol. 1991;1:263–276.
24. Tell GS,
Recruitment of
S, Fried
Fried
riied LP,
LP,
P, Hermanson
Her
ermanson B, Manolio TA, Newman
N wman AB,, Bor
Ne
Borhani
rhani NO. Recruitmen
adults 65 years
older
Health
Study.
Ann
Epidemiol.
year
ye
arss and ol
lde
derr as
a pparticipants
arti
ar
tici
ti
c pa
pant
ntss inn the
nt
the Cardiovascular
Car
a diiovasscu
cula
lar He
la
Heal
a th S
al
tudy
dy.. An
dy
A
n Ep
pid
idem
emioo
em
1993;3:358–366.
8–3
8–3
–366.
25. Ives DG,
Fitzpatrick
AL,
Psaty
BM,
Crowley
PM,
RG,
G Fi
G,
itz
tzpa
pat
pa
atrickk AL
L, Bi
Bild
l DE,
DE, P
saty
yB
M, Kuller
M,
Kulle
ll r LH
LH, C
row
wley P
M, Cruise
Cr
RG,
G Theroux
The
S. Surveillance
The
Cardiovascular
Health
Study.
ancee and
and
n ascertainment
asc
scer
erta
er
t in
ta
inme
ment
me
nt of
of cardiovascular
carddio
ova
vasc
s ular
sc
a eevents.
ar
vent
ve
n ss.. T
nt
he C
ardi
ar
diiovvas
ascu
cula
cu
larr He
la
H
alth
al
th S
Stu
tu
Ann Epidemiol.
1995;5:278–285.
m l. 19
miol
1995
95;5
95
5:2
278–285
285
85.
26. Piccini JP,
MF,
PN,
JP Hammill
Ha
illl BG,
il
BG Sinner
Si
MF
MF Jensen
J
PN Hernandez
Hernande
He
de AF,
AF Heckbert
Heckb
kbertt SR,
S
SR
R Benjamin
Benjami
B jamii EJ,
Curtis LH. Incidence and prevalence of atrial fibrillation and associated mortality among
Medicare beneficiaries, 1993-2007. Circ Cardiovasc Qual Outcomes. 2012;5:85–93.
27. Psaty BM, Manolio TA, Kuller LH, Kronmal RA, Cushman M, Fried LP, White R, Furberg
CD, Rautaharju PM. Incidence of and risk factors for atrial fibrillation in older adults.
Circulation. 1997;96:2455–2461.
28. Mozaffarian D, Psaty BM, Rimm EB, Lemaitre RN, Burke GL, Lyles MF, Lefkowitz D,
Siscovick DS. Fish intake and risk of incident atrial fibrillation. Circulation. 2004;110:368–373.
29. Aviv A, Hunt SC, Lin J, Cao X, Kimura M, Blackburn E. Impartial comparative analysis of
measurement of leukocyte telomere length/DNA content by Southern blots and qPCR. Nucleic
Acids Res. 2011;39:e134.
30. Fitzpatrick AL, Kronmal RA, Gardner JP, Psaty BM, Jenny NS, Tracy RP, Walston J,
Kimura M, Aviv A. Leukocyte telomere length and cardiovascular disease in the cardiovascular
health study. Am J Epidemiol. 2007;165:14–21.
20
DOI: 10.1161/CIRCEP.114.001781
31. Fitzpatrick AL, Kronmal RA, Kimura M, Gardner JP, Psaty BM, Jenny NS, Tracy RP,
Hardikar S, Aviv A. Leukocyte telomere length and mortality in the Cardiovascular Health
Study. J Gerontol A Biol Sci Med Sci. 2011;66:421–429.
32. Kimura M, Stone RC, Hunt SC, Skurnick J, Lu X, Cao X, Harley CB, Aviv A. Measurement
of telomere length by the Southern blot analysis of terminal restriction fragment lengths. Nat
Protoc. 2010;5:1596–1607.
33. Cawthon RM. Telomere measurement by quantitative PCR. Nucleic Acids Res. 2002;30:e47.
34. Lin J, Epel E, Cheon J, Kroenke C, Sinclair E, Bigos M, Wolkowitz O, Mellon S, Blackburn
E. Analyses and comparisons of telomerase activity and telomere length in human T and B cells:
insights for epidemiology of telomere maintenance. J Immunol Methods. 2010;352:71–80.
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
35. Mangino M, Hwang SJ, Spector TD, Hunt SC, Kimura M, Fitzpatrick
Christiansen
rick AL, Christians
nsen
ns
e L,
en
Petersen I, Elbers CC, Harris T, Chen W, Srinivasan SR, Kark JD, Benetos
A,, El S
Shamieh
net
etos
os A
hami
ha
mieh
mi
eh S,
Visvikis-Siest S, Christensen K, Berenson GS, Valdes AM, Viñuela A, Garcia
M,, Arne
Arnett
DK,
Gaarc
rciia
ia M
A
rneett D
Broeckel U, Province MA, Pankow JS, Kammerer C, Liu Y, Nalls M, Tishko
Tishkoff
S, Th
Thomas
koff
ko
ff S
Thom
omaas F, Ziv
om
E, Psaty BM,
Genome-wide
M,, Bis
Bis
i JC,
JC,
C Rotter
Rottter JI, Taylor KD, Smith E,
E, Schork
Schork NJ, Levy
Levyy D,
D Aviv A. Genome
meta-analysis
homeostasis
ysis
ysi
siis points to
to CTC1
CT
TC1
1 and
andd ZNF676
ZNF
NF67
676
76 as
a genes
gen
e ess regulating
regul
ulat
ul
atin
at
i g te
in
telo
telomere
l mere
lo
meer hom
om
meo
e stas
asis
as
i iin
is
n hu
hhumans.
Hum Mol Genet.
2012;21:5385–5394.
Genet. 2012;21:5385
85–539
85
3994.
36. Burstein
mechanisms
andd clinical
J
nB
B,, Natt
N
Na
Nattel
att
ttel S
S.. At
Atri
Atrial
iall ffibrosis:
ibrosi
siss: mec
si
cha
hani
nii
nisms
c in
cl
nic
icall relevance
rellevance in
in atriall ffibrillation.
fibrilla
i riill
ib
lla
l
Am Coll Cardiol.
2008;51:802–809.
a io
ardio
ol. 20
2008
08;5
08
; 1:
;5
1 8002–
2–80
809.
80
9
37. Robertss JD, Gollob
atrial
Goll
llob
ll
ob MH.
ob
MH.
H Impact
Imp
mpac
actt off ggenetic
ac
enet
en
ettic ddiscoveries
isco
is
cove
co
veri
ve
r es oonn the
the classification
clas
cl
clas
assi
sifi
si
fica
fi
cati
ca
tion
ti
on of
of lone atria
fibrillation. J A
Am C
Coll
Cardiol.
2010;55:705–712.
llll C
ddii l 20
2010;55:705
2010
10;55
55:70
7055 712
712
38. Blackburn EH. Telomeres and telomerase: their mechanisms of action and the effects of
altering their functions. FEBS Lett. 2005;579:859–862.
39. Laflamme MA, Murry CE. Heart regeneration. Nature. 2011;473:326–335.
40. Anversa P, Kajstura J, Leri A, Bolli R. Life and death of cardiac stem cells: a paradigm shift
in cardiac biology. Circulation. 2006;113:1451–1463.
41. Dewland TA, Vittinghoff E, Mandyam MC, Heckbert SR, Siscovick DS, Stein PK, Psaty
BM, Sotoodehnia N, Gottdiener JS, Marcus GM. Atrial ectopy as a predictor of incident atrial
fibrillation: a cohort study. Ann Intern Med. 2013;159:721–728.
21
DOI: 10.1161/CIRCEP.114.001781
Table 1: Baseline Characteristics of CHS Participants with and without Incident AF
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
Incident AF
n = 476
No AF
n = 1163
p value
Age (years)
72.8 ± 5.1
71.9 ± 5.1
<0.001
Male (%)
203 (42.6)
470 (40.4)
0.404
White Race (%)
434 (91.2)
989 (85.0)
85.0))
0.009
0.00
0.
0
00
Hypertension ((%))
163 (34.2)
(
)
351 ((30.2)
30 2))
00.358
35
Diabetes M
Mellitus
elllitus (%)
799 (16.6)
(16
166.6)
15
158
58 (13.6)
(133.66)
00.113
.111
Body Masss In
Index
nde
d x (kg/m
(kg/
(k
g/m
g/
m2)
27.0
27.00 ± 44.8
.8
26.8
26
.88 ± 44.5
.55
00.434
0.
433
Coronary Artery
Disease
(%)
A t
Dii
(%)
(25.6)
122 (25
122
(25 6)
182
182 (15.6)
(15
(15 6)
<0.001
<0
0 0000
Congestive Heart Failure (%)
29 (6.1)
33 (2.8)
0.002
Data are n (%) or mean ± standard deviation
22
DOI: 10.1161/CIRCEP.114.001781
Table 2: Clinical Demographics of the Surgical Cohort with Atrial and Leukocyte Telomere
Length Measurements
AF
n = 26
No AF
n=9
p value
64.6 ± 12.0
78.4 ± 8.2
0.003
Male
16 (61.5)
6 (66.7)
0.784
White Race
25 (96.2)
8 (88.
8.9)
8.
9)
(88.9)
0.3
0.
3
0.363
s on
sion
Hypertension
14 (53.9))
6 (66.7))
0.5
5
0.503
M
ellli
litu
tuss
tu
Diabetes Mel
Mellitus
( 9.
(1
9 2)
2
5 (19.2)
1 (1
((11.1)
1..1)
00.577
0.
5
Artery
t
Disease
Di
Coronary Artery
( 9.
(1
9 2)
2
5 (19.2)
4 (4
((44.4)
4.4)
4))
00.136
.11
Congestive Heart Failure
3 (11.5)
1 (11.1)
0.972
21 (80.8)
0 (0)
<0.001
Coronary Artery Bypass Grafting
2 (7.7)
4 (44.4)
0.012
Aortic Valve Replacement
1 (3.9)
4 (44.4)
0.003
Mitral Valve Surgery
2 (7.7)
2 (22.2)
0.238
Age (years)
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
Indication For Surgery
AF Ablation
Data are n (%) or mean ± standard deviation
23
DOI: 10.1161/CIRCEP.114.001781
Figure Legends:
Figure 1: Adjusted Survival Curves of Incident AF among Tertiles of Leukocyte Telomere
Length. HR denotes hazard ratio. The calculated HR is for tertiles of leukocyte telomere length
treated as an ordinal variable.
Figure 2: Impact of Leukocyte Telomere Length Tertiles on the Risk of Incident AF in a MultiDownloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
Variable Cox Regression Model. Leukocyte telomere length tertile was
categorical
as treated as a categ
eg
gor
o
variable. HR denotes hazard ratio; BMI denotes body mass index; CAD
AD denotes
deno
de
nottes
tes coronary
coro
co
rona
naary artery
disease; CHF
intervals.
HF
F ddenotes
e otes
en
ottes
e congestive
con
onngestive heart failure. Error
Erro
ror bars denote 95%
ro
% confidence intervals
Figure 3: Adjusted
Incident
Status
A ust
Adju
sted
ed Survival
Surviivall Curves
Curves of
of Inci
ide
dent
nt AF
AF by
by rs2736100
rs2
s273
s2
7361
73
6100
61
0 Genetic
00
Genetic
t Carrier
Car
arrier St
atus
t
Utilizing ann Additive
Add
ddiitive Genetic
Genneti
Ge
tic
i Model.
M del.
Mo
l HR
HR ddenotes
enotes hhazard
azardd ratio.
rattio.
Figure 4: Box plot comparisons of Atrial and Leukocyte Telomere Length among the Surgical
Cohort With and Without AF. Boxes represent 25th-75th quartiles and lines within boxes
represent median values. Outliers are displayed by distinct dots.
24
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
Telomere Length and the Risk of Atrial Fibrillation: Insights into the Role of Biological versus
Chronological Aging
Jason D. Roberts, Thomas A. Dewland, James Longoria, Annette L. Fitzpatrick, Elad Ziv, Donglei
Hu, Jue Lin, David V. Glidden, Bruce M. Psaty, Esteban G. Burchard, Elizabeth H. Blackburn,
Jeffrey E. Olgin, Susan R. Heckbert and Gregory M. Marcus
Downloaded from http://circep.ahajournals.org/ by guest on June 16, 2017
Circ Arrhythm Electrophysiol. published online November 8, 2014;
Circulation: Arrhythmia and Electrophysiology is published by the American Heart Association, 7272 Greenville Avenue,
Dallas, TX 75231
Copyright © 2014 American Heart Association, Inc. All rights reserved.
Print ISSN: 1941-3149. Online ISSN: 1941-3084
The online version of this article, along with updated information and services, is located on the
World Wide Web at:
http://circep.ahajournals.org/content/early/2014/11/08/CIRCEP.114.001781
Permissions: Requests for permissions to reproduce figures, tables, or portions of articles originally published in
Circulation: Arrhythmia and Electrophysiology can be obtained via RightsLink, a service of the Copyright Clearance
Center, not the Editorial Office. Once the online version of the published article for which permission is being
requested is located, click Request Permissions in the middle column of the Web page under Services. Further
information about this process is available in the Permissions and Rights Question and Answerdocument.
Reprints: Information about reprints can be found online at:
http://www.lww.com/reprints
Subscriptions: Information about subscribing to Circulation: Arrhythmia and Electrophysiology is online at:
http://circep.ahajournals.org//subscriptions/