Plasma Phospholipid Trans Fatty Acids, Fatal Ischemic
Heart Disease, and Sudden Cardiac Death in Older Adults
The Cardiovascular Health Study
Rozenn N. Lemaitre, PhD, MPH; Irena B. King, PhD; Dariush Mozaffarian, MD, MPH;
Nona Sotoodehnia, MD, MPH; Thomas D. Rea, MD, MPH; Lewis H. Kuller, MD, PhD;
Russel P. Tracy, PhD; David S. Siscovick, MD, MPH
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Background—Intake of trans fatty acids is associated with increased risk of coronary heart disease. Whether different
classes of trans fatty acids show similar associations is unclear. We previously reported an association of sudden cardiac
death with red cell membrane trans-18:2 but not trans-18:1 fatty acids. To extend these findings, we investigated the
associations of plasma phospholipid trans fatty acids with fatal ischemic heart disease (IHD) and sudden cardiac death.
Methods and Results—We conducted a case-control study nested in the Cardiovascular Health Study. We identified 214
cases of fatal IHD (fatal myocardial infarction and coronary heart disease death) between 1992 and 1998. We randomly
selected 214 controls, matched to cases on demographics, prevalent cardiovascular disease, and timing of blood draw.
Plasma phospholipid fatty acids were assessed in blood samples collected earlier. Higher levels of plasma phospholipid
trans-18:2 fatty acids were associated with higher risk of fatal IHD (odds ratio [OR] for interquintile range 1.68, 95%
confidence interval [CI] 1.21 to 2.33) after adjustment for risk factors and trans-18:1 levels. Trans-18:1 levels above
the 20th percentile were associated with lower risk (OR 0.34, 95% CI 0.18 to 0.63). In analyses limited to cases of
sudden cardiac death (n⫽95), higher levels of trans-18:2 fatty acids were associated with higher risk (OR 2.34, 95%
CI 1.27 to 4.31) and higher trans-18:1 with lower risk (OR 0.18, 95% CI 0.06 to 0.54).
Conclusions—Higher levels of trans-18:2 and lower levels of trans-18:1 fatty acids are associated with higher risks of fatal
IHD and sudden cardiac death. If confirmed, these findings suggest that current efforts at decreasing trans fatty acid
intake in foods should take into consideration the trans-18:2 content. (Circulation. 2006;114:&NA;-.)
Key Words: myocardial infarction 䡲 death, sudden 䡲 fatty acids 䡲 epidemiology
T
he use of partially hydrogenated oils by the food industry
has made trans fatty acids (TFAs) ubiquitous in the
Western diet. Unfortunately, TFA consumption may be detrimental to the health of the heart. In 4 large cohort studies,
higher dietary consumption of TFAs was associated with
higher risk of coronary heart disease.1– 4 In short-term feeding
trials, consumption of moderate to high levels of TFAs
resulted in higher low-density lipoprotein (LDL) cholesterol
when substituted for polyunsaturated fatty acids (PUFAs) or
carbohydrate and lower levels of high-density lipoprotein
(HDL) cholesterol when substituted for unsaturated or saturated fatty acids.5 On the basis of these studies, the Food and
Drug Administration (FDA) required food labels to indicate
the TFA content starting January 2006.6
Most studies have assessed consumption of total TFA.
However, several types of TFAs are produced during the
Clinical Perspective p 0000
partial hydrogenation of vegetable and seed oils, including
trans-isomers of oleic acid (trans-18:1) and trans-isomers of
linoleic acid (trans-18:2). Bacteria in ruminants also produce
small amounts of trans-isomers of palmitoleic acid (trans16:1). In a previous study of primary cardiac arrest (sudden
cardiac death) as a first clinical manifestation of heart
disease,7 we found that higher levels of trans-18:2 in red
blood cell membranes, a biomarker of intake, were associated
with higher risk. However, levels of trans-18:1, the most
abundant TFA in partially hydrogenated oils, and trans-16:1
were not associated with risk.
We used data from the Cardiovascular Health Study
(CHS),8 a prospective study of cardiovascular disease risk
factors among older men and women, to investigate the
Received February 10, 2006; revision received April 26, 2006; accepted May 10, 2006.
From the University of Washington, Cardiovascular Health Research Unit, Department of Medicine (R.N.L., N.S., T.D.R., D.S.S.), Cardiology Division
(N.S.), and Department of Epidemiology (D.S.S.), Seattle, Wash; the Public Health Sciences Division (I.B.K.), Fred Hutchinson Cancer Research Center,
Seattle, Wash; the Channing Laboratory, Department of Medicine (D.M.), Brigham and Women’s Hospital and Harvard Medical School, Boston, Mass;
the Public Health-Seattle and King County Emergency Medical Services Division (T.D.R.), Seattle, Wash; the Department of Epidemiology (L.H.K.),
University of Pittsburgh, Pittsburgh, Pa; and the Department of Pathology (R.P.T.), University of Vermont, Colchester, Vt.
Guest Editor for this article was Gregg C. Fonarow, MD.
Reprint requests to Rozenn Lemaitre, PhD, University of Washington, Cardiovascular Health Research Unit, 1730 Minor Ave, Suite 1360, Seattle, WA
98101. E-mail [email protected]
© 2006 American Heart Association, Inc.
Circulation is available at http://www.circulationaha.org
DOI: 10.1161/CIRCULATIONAHA.106.620336
1
2
Circulation
July 18, 2006
association of plasma phospholipid trans-18:2 and trans-18:1
fatty acids, a biomarker of intake, with fatal ischemic heart
disease (IHD) and sudden cardiac death.
Methods
Study Design and Participants
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We conducted a case-control study nested in the CHS.8 The CHS
cohort consists of 5888 noninstitutionalized men and women aged
ⱖ65 years at baseline, recruited from 4 US communities (Forsyth
County, North Carolina; Sacramento County, California; Washington County, Maryland; and Pittsburgh, Allegheny County, Pennsylvania). Initially 5201 participants were recruited between June 1989
and June 1990. An additional 687 blacks were recruited between
June 1992 and June 1993. The study was approved by each center’s
institutional review committee, and the subjects gave informed
consent.
We identified participants (cases) who experienced a fatal IHD
event between June 1992 and June 1998. IHD deaths were defined as
fatal myocardial infarction or fatal events that did not meet the
criteria for definite myocardial infarction in which participants had
chest pain within 72 hours of death or had a history of chronic IHD.
Myocardial infarction was defined on the basis of cardiac enzyme
levels, chest pain, and serial ECG changes. All IHD events were
classified by a morbidity and mortality committee. One of the
authors (N.S., a cardiologist) reviewed all fatal IHD records, including hospital records; interviews with physicians, next-of-kin, and/or
witnesses; death certificates; and autopsy reports to identify sudden
cardiac deaths. Operationally, sudden cardiac death was defined as a
sudden pulseless condition of cardiac origin in a previously stable
individual that occurred out of the hospital or in the emergency
department. By definition, sudden cardiac death cases could not have
a life-threatening noncardiac comorbidity or be under hospice or
nursing home care. A blinded second review by another author (T.R)
of a random sample of 70 of these death records showed an 88%
interreviewer agreement and ␬⫽0.74 for sudden cardiac death.
We excluded participants who died in nursing homes and those
who used fish oil supplements at the time of the blood draw (fish oil
use would change fatty acid membrane composition). These analyses
included 214 fatal IHD cases. Of those, 95 were identified as sudden
cardiac deaths.
For each case, 1 control subject was randomly selected from the
CHS participants who did not experience a fatal IHD event and did
not use fish oil supplements, individually matched to the case subject
on the basis of gender, clinic site, entry cohort, age (⫾5 years), time
of blood draw (⫾90 days), presence or absence of cardiovascular
disease at the time of the blood draw, and a follow-up duration ⱖ
that of the case subject.
Measurement of Plasma Phospholipid Fatty Acids
Fasting blood samples were obtained during the 1992 to 1993 clinic
visit, the baseline for the present analysis. The blood samples were
collected on average 3.0⫾1.6 years before the events.
Plasma samples were stored at ⫺70°C until they were analyzed.
Total lipids were extracted by the method of Folch et al.9 Phospholipids were separated from neutral lipids by 1-dimensional thin-layer
chromatography with 250-␮m Silica Gel G plates (Analtech Inc,
Newark, Del) and a 67.5:15:0.75 hexane/diethyl ether/acetic acid
development solvent with 0.005% butylated hydroxytoluene. The
phospholipid fractions were then directly transesterified to prepare
fatty acid methyl esters (FAMEs) by the method of Lepage and
Roy.10 FAMEs of individual fatty acids were separated by gas
chromatography. The FAMEs were injected in a split mode (1:50)
into a gas chromatography system (model 6890, Agilent Technologies Inc, Palo Alto, Calif). The gas chromatograph was equipped
with a flame ionization detector, electronic pressure control, automatic sampler, and Chemstation software (Agilent Technologies Inc,
Palo Alto, Calif). The FAMEs were separated on a 100-m⫻0.25-mm
internal-diameter capillary silica column with a 0.2-␮m coating
(SP2560, Supelco, Bellefonte, Pa). The carrier gas was helium at 1.3
mL/min; makeup gas was nitrogen at 35.1 mL/min. Column linear
velocity was set at 20.0 cm/s at an oven temperature of 200°C. The
injector and detector port temperatures were both set at 250°C. The
oven temperature (160°C at the start) and electronic pressure (50 psi
at the start) were controlled by a set program for a total run of 60
minutes to optimize the separation of TFAs. We measured 10 TFAs
in the plasma phospholipids: 5 trans-18:1 fatty acids (12 trans-18:1,
11 trans-18:1, 10 trans-18:1, 9 trans-18:1, and a mixture of 6 to 9
trans-18:1); 3 trans-18:2 fatty acids (9 cis, 12 trans-18:2; 9 trans, 12
cis-18:2; and 9 trans, 12 trans-18:2); and 2 trans-16:1 (7 trans-16:1
and 9 trans-16:1). The method was not optimized for the measurement of conjugated linoleic acid isomers, which were not assessed.
Fatty acid concentrations are expressed as percentages of total fatty
acids by weight.
Identification, precision, and accuracy were evaluated with model
mixtures of known FAMEs and an established in-house qualitycontrol pool. The identification of plasma phospholipid fatty acids
has been confirmed by gas chromatography coupled to mass spectroscopy at the US Department of Agriculture Lipid Laboratory in
Peoria, Ill. In addition, TFA identification has been verified by silver
ion thin-layer chromatography.11 Interassay coefficients of variation
in the quality-control pool samples for TFAs were as follows:
trans-16:1, 13%; trans-18:1, 8%; and trans-18:2, 11%. Laboratory
analyses were conducted by technicians blinded to case and control
status.
Assessment of Other Risk Factors
At the time of the blood draw, participants completed standardized
questionnaires on medical history, health status, and personal habits
and underwent a clinic examination that included blood pressure and
anthropometric measurements.8 Dietary intake, assessed from a
picture-sort food-frequency questionnaire, was assessed ⬇3 years
before the blood draws on a subset of participants included in the
present report (150 matched pairs). Prevalent clinical cardiovascular
disease was defined as a history of myocardial infarction, angina,
congestive heart failure, stroke, coronary artery bypass, and
angioplasty.
Statistical Analysis
We compared the distribution of risk factors and means of plasma
phospholipid TFA among cases and their matched controls using
paired t tests. Categorical variables with ⬎2 levels were compared
with ␹2 tests. We compared risk factor distributions across quintiles
of TFA among controls using ␹2 tests (categorical variables) and
ANOVA. Correlations between plasma phospholipid fatty acids
were determined as Pearson correlations adjusted for age.
We used conditional logistic regression to obtain odds ratios (ORs;
estimates of relative risks) of fatal IHD and sudden cardiac death
associated with increasing levels of plasma phospholipid TFA.
Statistical significance was assessed with the likelihood ratio test.
Using the lowest quintile of TFA distribution as the reference, we
assessed the risk of fatal IHD associated with each upper quintile of
TFA. These categorical analyses were consistent with a linear
association with risk of trans-18:2. We used linear models to
estimate risk associated with trans-18:2 in the main analyses, and we
present ORs for trans-18:2 levels corresponding to the 80th percentile of the distribution of these fatty acids compared with trans-18:2
levels corresponding to the 20th percentile (ie, ORs for the interquintile range). Categorical analyses with quintiles of trans-18:1 were
most compatible with a threshold higher risk in the lowest quintile.
In the main analyses, we estimated risk for trans-18:1 levels above
versus below the 20th percentile of the trans-18:1 distribution.
Sensitivity analyses with alternate cut points corresponding to the
15th and 25th percentiles gave similar results. Interaction between
trans-18:2 and trans-18:1 fatty acids was evaluated by testing
whether addition of cross-products between trans-18:1 and trans18:2 improved the model.
The covariates used in the analyses were from the examination of
the blood collection. The analyses were based on the updated CHS
databases, which incorporated minor corrections up to March 2002.
Lemaitre et al
Statistical analyses were performed with STATA 8.2 (StataCorp LP,
College Station, Tex).
The authors had full access to the data and take responsibility for
its integrity. All authors have read and agree to the manuscript as
written.
Results
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Given the matching, age and sex distribution and prevalence
of prior clinical coronary heart disease were similar in cases
and controls (Table 1). As expected, other traditional risk
factors for IHD, such as current smoking and diabetes
mellitus, were more prevalent in cases than in controls. In
addition, cases were more likely to report lower education,
lower income, and poor health. In univariate analyses, mean
levels of TFA did not differ significantly between cases and
controls (Table 1).
There were few differences in clinical characteristics between participants with high and low levels of membrane
trans-18:2 and trans-18:1 fatty acids; no apparent differences
in lifestyle characteristics; and among the participants with
dietary data, no differences in nutritional characteristics
assessed 3 years earlier (data not shown). Participants with
high levels of trans-18:2 were more likely to be female (53%
in the highest quintile [Q5] and 28% in the lowest quintile
[Q1]) and had lower mean body weight (Q5 73.6 kg; Q1 75.4
kg). Participants with high levels of trans-18:1 had lower
mean levels of insulin (Q5 9.9 ␮/mL; Q1 17.7 ␮/mL). Plasma
phospholipids levels of trans-18:2 were positively associated
with trans-18:1 levels (r⫽0.42, P⬍0.001), and levels of
trans-18:2 and trans-18:1 fatty acids were negatively associated with docosahexaenoic acid plus eicosapentaenoic acid
levels (r⫽⫺0.17, P⫽0.01 and r⫽⫺0.15, P⫽0.03,
respectively).
In multivariate analyses, total TFA and trans-16:1 fatty
acids were not associated with risk of fatal IHD (Table 2).
However, higher levels of trans-18:2 fatty acids were associated with higher risk. An increase in trans-18:2 from 0.22%
to 0.35% of total fatty acids, corresponding to the interquintile range, was associated with 30% higher risk (OR 1.31;
95% confidence interval [CI] 0.99 to 1.72) in analyses that
accounted for the matching factors and further adjusted for
diabetes, congestive heart failure, stroke, smoking status,
education, and levels of docosahexaenoic acid plus eicosapentaenoic acid. With further adjustment for trans-18:1,
trans-18:2 fatty acids were associated with a 68% higher risk
(OR 1.68; 95% CI 1.21 to 2.33). Risk estimates in increasing
quintiles of trans-18:2 were 1.0 (reference), 0.87 (95% CI
0.41 to 1.84), 1.08 (95% CI 0.52 to 2.28), 3.20 (95% 1.42 to
7.20), and 4.52 (95% CI 1.83 to 11.20) with adjustment for
risk factors and trans-18:1.
Higher levels of trans-18:1 were associated with lower risk
of fatal IHD. After adjustment for risk factors and levels of
trans-18:2, risk estimates in increasing quintiles of trans-18:1
fatty acids were 1.0 (reference), 0.29 (95% CI 0.14 to 0.61),
0.32 (95% CI 0.15 to 0.70), 0.45 (95% CI 0.21 to 0.97), and
0.38 (95% CI 0.17 to 0.86), consistent with a threshold in risk
at the 20th percentile. Compared with lower levels, trans18:1 levels above the 20th percentile were associated with a
66% lower risk (OR 0.34; 95% CI 0.18 to 0.63; Table 2).
Trans Fatty Acids and Fatal Ischemic Heart Disease
3
We found no evidence of interaction between trans-18:2
and trans-18:1 (P⫽0.42). Further adjustment for the covariates listed in Table 1 did not change the results appreciably.
Similar results were obtained in analyses restricted to participants in good-to-excellent health at the time of the blood
draw.
In analyses restricted to the 95 cases with sudden cardiac
death and their matched controls, higher trans-18:2 fatty
acids that corresponded to the interquintile range were associated with ⬎2-fold higher risk of sudden cardiac death (OR
2.34; 95% CI 1.27 to 4.31) after adjustment for trans-18:1
fatty acids and the covariates listed in Table 2. Higher
trans-18:1 was associated with lower risk of sudden cardiac
death (OR for levels above the 20th percentile, 0.18; 95% CI
0.06 to 0.54). ORs among cases whose events were not
believed to be sudden cardiac deaths were 1.54 (95% CI 1.01
to 2.37) for higher trans-18:2 corresponding to the interquintile range and 0.47 (95% CI 0.20 to 1.12) for levels of
trans-18:1 above the 20th percentile.
Discussion
In this study, higher plasma phospholipid levels of transisomers of linoleic acid (trans-18:2) in blood samples collected on average 3 years before the event were associated
with higher risk of fatal IHD and sudden cardiac death among
older adults. In contrast, higher levels of trans-isomers of
oleic acid (trans-18:1) were associated with lower risk. These
associations were independent of demographics, clinical and
lifestyle risk factors, and plasma phospholipid levels of n-3
PUFAs from seafood.
The study results are consistent with our findings from a
population-based case-control study of sudden cardiac
death conducted in the greater Seattle area.7 In the prior
investigation, higher levels of trans-18:2 in red blood cell
membranes were associated with increased risk of sudden
cardiac death (OR corresponding to the interquintile range
3.1, 95% CI 1.7 to 5.4). Of note, the prior study differed
from the present one with regard to the study population
age (58 versus 77 years old in the present study) and
preexisting conditions (no prior clinically diagnosed heart
disease in the prior study versus subjects with and without
heart disease in the present study), the exposure assessment (red cell membrane fatty acids in blood samples
collected by paramedics at the time of the event versus
plasma phospholipid fatty acid in blood collected on
average 3 years before the events), and the main outcome
(sudden cardiac death versus fatal IHD). Perhaps due to the
study differences, the OR of fatal IHD corresponding to
the interquintile range of plasma phospholipid trans-18:2
was somewhat lower in the present study, 1.7 (95% CI 1.2
to 2.3). However, the associations appeared similar in
analyses that compared upper with lowest quintiles, although the CIs were large: Participants in the upper
quintile of trans-18:2 appeared to be at 4-fold higher risk
of fatal IHD in the present study (OR 4.5, 95% CI 1.8 to
11.2) and at 4-fold higher risk of sudden cardiac death in
the prior study (OR 4.3, 95% CI 1.4 to 13.3, unpublished
data).
4
Circulation
TABLE 1.
July 18, 2006
Characteristics of Cases of Fatal IHD and Matched Controls
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Age, y
Male gender, %
White race, %
Education, %
No high school
High school
College
Study site, %
Bowman Gray (North Carolina)
UC Davis (Sacramento)
Johns Hopkins (Maryland)
University of Pittsburgh
Annual income, %
⬍$12 000
$12 000–$25 000
ⱖ$25 000
Cardiovascular disease, %
Myocardial infarction, %
Stroke, %
Congestive heart failure, %
Treated diabetes, %
Treated hypertension, %
Weight, kg
Body mass index, kg/m2
Systolic blood pressure, mm Hg
Diastolic blood pressure, mm Hg
Total cholesterol, mg/dL
HDL, mg/dL
LDL, mg/dL
Fasting glucose, mg/dL
Insulin level, ␮/mL
Glucose/insulin ratio
Fibrinogen, mg/dL
Common carotid maximum wall thickness, mm
Internal carotid maximum wall thickness, mm
Former smokers, %
Current smokers, %
Family history of MI, %
Regular use of aspirin, %
Physical activity, kcal
Self-reported health at blood draw, excellent, very good, or good, %
Trans-18:2†
Trans-18:1†
Trans-16:1†
18:2n6†
18:3n3†
DHA⫹EPA†
Total n-3 PUFAs†
Total n-6 PUFAs†
Cases
(n⫽214)
Controls
(n⫽214)
77.3 (6.1)
60.3
81.3
76.6 (5.5)
60.3
83.6
37.9
30.8
31.3
28.0
30.4
41.6
23.8
24.3
25.2
26.6
23.8
24.3
25.2
26.6
33.8
32.4
33.8
59.8
30.8
14.0
19.6
19.6
53.3
74.9 (8.2)
26.7 (4.6)
138.7 (22.5)
70.7 (12.1)
205.3 (37.5)
48.2 (13.1)
126.6 (32.0)
122.1 (48.6)
19.9
41.8
38.4
59.8
28.5
8.4
13.6
10.8
52.1
76.2 (8.2)
27.0 (4.2)
136.8 (21.8)
70.5 (11.4)
204.0 (43.9)
49.7 (12.7)
125.0 (36.2)
106.7 (28.7)
21.9 (50.0)
10.8 (6.3)
351.2 (81.2)
1.18 (0.27)
1.67 (0.59)
48.1
15.4
41.6
44.1
1152 (1549)
63.1
0.31 (0.11)
1.95 (0.71)
0.28 (0.09)
20.2 (2.6)
0.16 (0.05)
3.64 (1.10)
4.65 (1.17)
35.3 (1.93)
13.0 (9.3)
10.4 (4.8)
332.6 (65.7)
1.15 (0.25)
1.61 (0.64)
56.8
5.6
33.0
42.1
1215 (1511)
77.6
0.30 (0.11)
2.01 (0.77)
0.28 (0.07)
20.0 (2.4)
0.15 (0.05)
3.76 (1.32)
4.77 (1.41)
35.6 (2.00)
P From Paired
t Tests
*
*
0.23
0.04
*
0.005
MI indicates myocardial infarction; DHA⫹EPA, docosahexaenoic acid plus eicosapentaenoic acid.
Values in the table are mean (SD) unless otherwise indicated.
*Matching factors.
†Percent of TFAs.
*
0.55
0.06
0.07
0.008
0.76
0.07
0.51
0.34
0.88
0.74
0.21
0.66
0.0001
0.02
0.40
0.01
0.25
0.41
0.004
0.08
0.67
0.66
0.0004
0.17
0.37
0.94
0.41
0.20
0.29
0.31
0.09
Lemaitre et al
TABLE 2.
Trans Fatty Acids and Fatal Ischemic Heart Disease
Association of Plasma Phospholipid Trans Fatty Acids With Fatal IHD in the CHS
Unadjusted*
Adjusted*
Separate
Models
Trans-18:1 and
Trans-18:2 Assessed
Simultaneously
Separate
Models
Trans-18:1 and
Trans-18:2 Assessed
Simultaneously
Total†
0.90 (0.65–1.24)
䡠䡠䡠
0.94 (0.65–1.34)
䡠䡠䡠
Trans-16:1†
1.04 (0.72–1.51)
0.95 (0.64–1.42)
Trans-18:2†
1.20 (0.94–1.53)
䡠䡠䡠
1.42 (1.07–1.87)
1.31 (0.99–1.72)
䡠䡠䡠
1.68 (1.21–2.33)
Trans-18:1‡
0.62 (0.39–0.99)
0.47 (0.28–0.80)
0.53 (0.31–0.90)
0.34 (0.18–0.63)
Trans Fatty
Acids
5
Values are expressed as OR (95% CI).
*Unadjusted analyses were conditioned on the matching factors of age, gender, presence of cardiovascular
disease, clinic site, and time of blood draw. Adjusted analyses were further adjusted for diabetes mellitus, low
education, current and former smoking, congestive heart failure, a history of stroke, and docosahexaenoic acid plus
eicosapentaenoic acid plasma phospholipid levels.
†The ORs in the table are for the interquintile range of trans fatty acid levels. Interquintile ranges were 1.39% of
TFAs (total trans fatty acids), 0.13% (trans-16:1), and 0.13% (trans-18:2).
‡The ORs for trans-18:1 fatty acids are for the comparison of levels above with levels below the 20th percentile
of the trans-18:1 distribution.
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In the prior study, we reported no association of trans18:1 levels with risk of sudden death (OR for interquintile
range 0.8, 95% CI 0.5 to 1.2). However, when we
reanalyzed the data, we found a 60% lower risk of sudden
death associated with red cell membrane trans-18:1 levels
above the 20th percentile (OR 0.4, 95% CI 0.2 to 0.9), in
good agreement with the finding from the present study
(OR of fatal IHD associated with plasma phospholipid
levels of trans-18:1 above the 20th percentile 0.3, 95% CI
0.2 to 0.9). Taken together, these 2 observational studies
suggest that dietary intake of trans-18:2 may increase the
risk of fatal IHD and sudden cardiac death and that
different types of trans-isomers in the diet may influence
risks differently.
The association of trans-18:2 with the risk of fatal IHD
might be due to an effect on atherosclerosis. In support of
this possibility, higher levels of trans-18:2 in adipose
tissue, but not high levels of trans-18:1, were associated
with higher risk of nonfatal myocardial infarction in a
case-control study among Costa Ricans12; however, the
trans-isomer composition of adipose tissue in the Costa
Rican population is unusual. Whether the association of
trans-18:2 with nonfatal myocardial infarction can be
generalized to other populations needs to be investigated.
In other epidemiological studies of TFA and coronary
heart disease, trans-18:2 was not assessed.1– 4,13 Additionally, documented adverse effects of TFAs on blood lipids,5
and possibly on inflammation14 –16 and endothelial function,17 do not explain different associations of trans-18:1
and trans-18:2 with IHD death and sudden death.
The association of trans-18:2 with fatal IHD and sudden
cardiac death might also be due to proarrhythmic effects.
Dietary fatty acids, particularly n-3 PUFAs, can influence
myocardial vulnerability to triggers of arrhythmia in experimental settings,18,19 and in vitro studies with cardiac
myocytes suggest an effect of n-3 PUFAs on action
potential and on sodium and calcium ion channel function.20 Possible effects of trans-18:2 and other trans-
isomers on ventricular fibrillation and cardiac ion channels
need to be investigated.
The association of higher levels of trans-18:1 with lower
risk of fatal IHD and sudden cardiac death is new and
needs to be confirmed by further studies. It has been
suggested that the metabolic effects of trans-vaccenic acid,
one of the trans-18:1 isomers, might have beneficial
metabolic effects in part because it can be desaturated to
conjugated linoleic acid.21 Of note, trans-vaccenic acid
was highly correlated to the other trans-18:1 isomers in the
present study (correlation coefficients between 0.8 and
0.9), which precludes an investigation of the associations
of the separate trans-18:1 isomers.
We have now observed in 2 different studies that
trans-18:1 and trans-18:2 fatty acids differ in their association with risk. Although further studies are needed to
investigate differences in effects of these 2 subclasses of
TFA, in vitro studies suggest fundamental biological
differences. In particular, trans-18:2 fatty acids are preferentially incorporated in the sn-2 (middle) position of
phospholipids, where PUFAs are typically found. In contrast, trans-18:1 fatty acids are incorporated equally in the
sn-1 position, where saturated fatty acids are usually
found. Furthermore, the fatty acid composition of phospholipids can affect membrane properties. For example,
changes in membrane phospholipid composition within the
range of normal variation have been shown to influence the
activity of the sodium ion channel in red blood cells.22
Trans-18:2 fatty acids are found in small amounts in
partially hydrogenated oils, nonhydrogenated refined oils,
and dairy products. In nonhydrogenated oils, trans-18:2
fatty acids are formed by isomerization of linoleic acid
during the process of deodorization due to the heat
treatment.23 Consequently, trans-18:2 fatty acids are present in refined soybean, sunflower, corn, peanut, and canola
oils, although trans-18:1 levels are very low or undetectable.24 Furthermore, trans-18:2 fatty acids can be produced
during the frying of foods, which raises the possibility that
6
Circulation
July 18, 2006
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food preparation, both by the food industry and by consumers, might affect food levels of trans-18:2 fatty acids.25
The relative contribution of the different sources of dietary
trans-18:2 fatty acids is unknown and likely varies with
study populations and trends in food manufacturing. Consequently, there are currently no good data on the different
food sources of trans-18:2 and trans-18:1 fatty acids. In
addition, the relationship of dietary trans-18:2 fatty acids
to plasma levels has not been studied. However, estimates
of dietary trans-18:2 fatty acids correlate with levels of
trans-18:2 fatty acids in adipose tissue, another biomarker
of intake.26
In the present study, the correlation of plasma phospholipid trans-18:2 and trans-18:1 fatty acids was only 0.4.
Although measurement error might lower the correlation,
the modest correlation of trans-18:2 and trans-18:1 fatty
acids suggests the presence of both subclasses in some but
not all foods with TFA. Because the food content of
trans-18:2 fatty acids may be largely unknown to the food
industry, the labeling of TFA in foods might not include
these potentially harmful isomers.
The present study has several strengths. Selection of
controls within a prospectively enrolled cohort provides
control subjects representative of the noncases. Blood
samples were collected prospectively. The matching design and the wealth of information on risk factors in the
CHS minimize the possibility of confounding. The use of
a biomarker of dietary TFA allowed us to assess different
trans-isomers.
The study also has limitations. Because of the observational nature of the study, we cannot eliminate the possibility of residual confounding by imprecisely measured
risk factors or unmeasured risk factors. In particular, we
had incomplete dietary information, which was assessed 3
years before the blood draws. The higher risk associated
with lower trans-18:1 fatty acids was confined to the
lowest quintile, and residual confounding in the lowest
quintile cannot be eliminated. However, when we reanalyzed data from our Seattle study using quintiles, we
observed a similarly higher risk with lower levels of
trans-18:1 fatty acids, as described above. The number of
study subjects was modest, and we had limited power to
investigate effect modification. The levels of TFAs in
plasma phospholipids may be subject to laboratory and
biological variation; however, we measured fatty acid
levels in cases and their matched controls in the same
chromatography runs to minimize differential laboratory
variation between cases and controls. Nondifferential error
in measurement, as expected from moderately high coefficients of variation, would bias the results toward the null.
Summary
Higher levels of plasma phospholipid trans-18:2 fatty acids
are associated with higher risk of fatal IHD and sudden
cardiac death among older adults. In contrast, low levels of
trans-18:1 fatty acids are associated with higher risks. If
confirmed, these findings suggest that current efforts at
decreasing trans fatty acid intake in foods should take into
consideration the trans-18:2 fatty acid content.
Sources of Funding
The research reported in this article was supported by contracts
N01-HC-85079 through N01-HC-85086, N01-HC-35129, N01 HC15103, N01 HC-55222, and U01 HL080295 from the National Heart,
Lung, and Blood Institute, with additional contribution from the
National Institute of Neurological Disorders and Stroke. A full list of
participating CHS investigators and institutions can be found at
http://www.chs-nhlbi.org.
Disclosures
None.
References
1. Oomen CM, Ocke MC, Feskens EJ, van Erp-Baart MA, Kok FJ,
Kromhout D. Association between trans fatty acid intake and 10-year risk
of coronary heart disease in the Zutphen Elderly Study: a prospective
population-based study. Lancet. 2001;357:746 –751.
2. Ascherio A, Rimm EB, Giovannucci EL, Spiegelman D, Stampfer M,
Willett WC. Dietary fat and risk of coronary heart disease in men: cohort
follow up study in the United States. BMJ. 1996;313:84 –90.
3. Pietinen P, Ascherio A, Korhonen P, Hartman AM, Willett WC, Albanes
D, Virtamo J. Intake of fatty acids and risk of coronary heart disease in
a cohort of Finnish men: the Alpha-Tocopherol, Beta-Carotene Cancer
Prevention Study. Am J Epidemiol. 1997;145:876 – 887.
4. Willett WC, Stampfer MJ, Manson JE, Colditz GA, Speizer FE, Rosner
BA, Sampson LA, Hennekens CH. Intake of trans fatty acids and risk of
coronary heart disease among women. Lancet. 1993;341:581–585.
5. Mensink RP, Zock PL, Kester AD, Katan MB. Effects of dietary fatty
acids and carbohydrates on the ratio of serum total to HDL cholesterol
and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled
trials. Am J Clin Nutr. 2003;77:1146 –1155.
6. US Food and Drug Administration. FDA acts to provide better information to consumers on trans fats. Available at: http://www.fda.gov/oc/
initiatives/transfat/. Accessed September 20, 2005.
7. Lemaitre RN, King IB, Raghunathan TE, Pearce RM, Weinmann S,
Knopp RH, Copass MK, Cobb LA, Siscovick DS. Cell membrane
trans-fatty acids and the risk of primary cardiac arrest. Circulation.
2002;105:697–701.
8. Fried LP, Borhani NO, Enright P, Furberg CD, Gardin JM, Kronmal RA,
Kuller LH, Manolio TA, Mittelmark MB, Newman A, O’Leary DH, Psaty
B, Rautaharju P, Tracy RP, Weiler PG. The Cardiovascular Health Study:
design and rationale. Ann Epidemiol. 1991;1:263–276.
9. Folch J, Lees M, Sloane GH. A simple method for isolation and purification of total lipids from animal tissues. J Biol Chem. 1957;226:
497–509.
10. Lepage G, Roy CC. Direct transesterification of all lipids in a one-step
reaction. J Lipid Res. 1986;27:114 –120.
11. Ulberth F, Henninger M. Simplified method for the determination of trans
monoenes in edible fats by TLC-GLC. J Am Oil Chem Soc. 1992;69:
829 – 831.
12. Baylin A, Kabagambe EK, Ascherio A, Spiegelman D, Campos H. High
18:2 trans-fatty acids in adipose tissue are associated with increased risk
of nonfatal acute myocardial infarction in Costa Rican adults. J Nutr.
2003;133:1186 –1191.
13. Aro A, Kardinaal AF, Salminen I, Kark JD, Riemersma RA, DelgadoRodriguez M, Gomez-Aracena J, Huttunen JK, Kohlmeier L, Martin BC,
Martin-Moreno JM, Mazaev VP, Ringstad J, Thamm M, van’t Veer P,
Kok FJ. Adipose tissue isomeric trans fatty acids and risk of myocardial
infarction in nine countries: the EURAMIC study. Lancet. 1995;345:
273–278.
14. Baer DJ, Judd JT, Clevidence BA, Tracy RP. Dietary fatty acids affect
plasma markers of inflammation in healthy men fed controlled diets: a
randomized crossover study. Am J Clin Nutr. 2004;79:969 –973.
15. Mozaffarian D, Pischon T, Hankinson SE, Rifai N, Joshipura KE, Willett
WC, Rimm EB. Dietary intake of trans fatty acids and systemic inflammation in women. Am J Clin Nutr. 2004;79:606 – 612.
16. Mozaffarian D, Rimm EB, King IB, Lawler RL, McDonald GB, Levy
WC. Trans fatty acids and systemic inflammation in heart failure.
Am J Clin Nutr. 2004;80:1521–1525.
17. Lopez-Garcia E, Schulze MB, Meigs JB, Manson JE, Rifai N, Stampfer
MJ, Willett WC, Hu FB. Consumption of trans fatty acids is related to
Lemaitre et al
18.
19.
20.
21.
22.
plasma biomarkers of inflammation and endothelial dysfunction. J Nutr.
2005;135:562–566.
Charnock JS. Dietary fats and cardiac arrhythmia in primates. Nutrition.
1994;10:161–169.
Billman GE, Kang JX, Leaf A. Prevention of sudden cardiac death by
dietary pure omega-3 polyunsaturated fatty acids in dogs. Circulation.
1999;99:2452–2457.
Kang JX, Leaf A. Prevention of fatal cardiac arrhythmias by polyunsaturated fatty acids. Am J Clin Nutr. 2000;71:202S–207S.
Aro A. Complexity of issue of dietary trans fatty acids. Lancet. 2001;
357:732–733.
Engelmann B, Op den Kamp JA, Roelofsen B. Replacement of molecular
species of phosphatidylcholine: influence on erythrocyte Na transport.
Am J Physiol. 1990;258:C682–C691.
Trans Fatty Acids and Fatal Ischemic Heart Disease
7
23. Kemeny Z, Recseg K, Henon G, Kovari K, Zwobada F. Deodorization of
vegetable oils: prediction of trans polyunsaturated fatty acid content. J Am
Oil Chem Soc. 2001;78:973–979.
24. Aro A, Van Amelsvoort J, Becker W, van Erp-Baart MA, Kafatos A, Leth T,
van Poppel G. Trans fatty acids in dietary fats and oils from 14 European
countries: the TRANSFAIR Study. J Food Comp Anal. 1998;11:137–149.
25. Sebedio J, Chardigny J. Physiological effects of trans and cyclic fatty
acids. In: Perkins E, Erickson M, eds. Deep Frying Chemistry:
Nutrition and Practical Applications. Champaign, Ill: AOCS Press;
1996:183–209.
26. Lemaitre RN, King IB, Patterson RE, Psaty BM, Kestin M, Heckbert SR.
Assessment of trans-fatty acid intake with a food frequency questionnaire
and validation with adipose tissue levels of trans-fatty acids. Am J Epidemiol. 1998;148:1085–1093.
CLINICAL PERSPECTIVE
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As mandated by the Food and Drug Administration, nutritional labels on food products now indicate the total content of
trans fatty acids. However, the present study suggests that not all trans fatty acids carry the same risk. We studied the
association of trans fatty acids in plasma phospholipids, a marker of dietary intake, with fatal ischemic heart disease (fatal
myocardial infarction and coronary heart disease death) and sudden cardiac death in a case-control study nested in a cohort
study, the Cardiovascular Health Study. In multivariate analyses, elevated levels of a specific type of trans fatty acid
(trans-18:2) were associated with increased risk of fatal ischemic heart disease and sudden cardiac death. Trans-18:2 are
minor trans fatty acids that derive from linoleic acid, the major polyunsaturate in commercial oils, and are produced by
heat treatment of the oils. Although higher intake of these minor trans fatty acids appeared to increase risk, higher levels
of the trans fatty acids commonly produced during partial hydrogenation (“trans-18:1”) were associated with lower risks.
A reanalysis of data from a previous population-based case-control study showed nearly identical associations of red blood
cell membrane trans-18:2 fatty acids with higher risk and trans-18:1 fatty acids with lower risk of sudden cardiac arrest.
Future studies need to distinguish between trans-18:2 and trans-18:1 fatty acids to reassess the risks and possible benefits
of different trans fatty acids.
Plasma Phospholipid Trans Fatty Acids, Fatal Ischemic Heart Disease, and Sudden
Cardiac Death in Older Adults. The Cardiovascular Health Study
Rozenn N. Lemaitre, Irena B. King, Dariush Mozaffarian, Nona Sotoodehnia, Thomas D. Rea,
Lewis H. Kuller, Russel P. Tracy and David S. Siscovick
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Circulation. published online July 3, 2006;
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