INTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY
Int[ J[ Geriatr[ Psychiatry 04\ 742Ð751 "1999#
DECLINE ACROSS DIFFERENT DOMAINS OF
COGNITIVE FUNCTION IN NORMAL AGEING]
RESULTS OF A LONGITUDINAL POPULATION!
BASED STUDY USING CAMCOG
SARAH CULLUM0\ FELICIA A[ HUPPERT1\ MAGNUS McGEE2\ TOM DENING3\ ANNE AHMED0\ EUGENE S[ PAYKEL1
AND CAROL BRAYNE0
0
Department of Community Medicine\ University of Cambrid`e\ UK
1
Department of Psychiatry\ University of Cambrid`e\ UK
2
MRC Biostatistics Unit\ Cambrid`e\ UK
3
Psychiatric Services for the Elderly\ Addenbrookes NHS Trust\ Cambrid`e\ UK
ABSTRACT
Dementia is an important cause of disability in the elderly[ There is evidence that cognitive impairment in dementia
is on a continuum with cognitive impairment in the non!demented elderly[ In order to investigate this possibility\ we
need detailed knowledge about the population distribution of cognitive function and change in cognitive function[
The aim of this study is to describe the change in di}erent domains of cognitive function over 3 years in a population!
based sample of non!demented elderly people\ and to investigate the e}ect of sociodemographic variables and baseline
cognitive function on change in each of the cognitive domains[ Respondents from two group general practice lists
"n 492# were interviewed using the Cambridge Cognitive Examination "CAMCOG# at the incidence wave of the
Cambridge City Over!64 Cohort Study and after a mean time period of 2[8 years[ One hundred and thirty _ve of 101
non!demented subjects seen at follow!up completed the CAMCOG at both interviews[ The annual rate of change in
total CAMCOG score was −0[5 points per year "p ³ 9[990#[ There was statistically signi_cant decline in all of the
CAMCOG subscales[ Greater decline in the Memory subscale was associated with less education "p 9[92#[ Greater
decline in the Attention:Calculation subscale was associated with manual social class "p 9[94#[ Greater decline in
the Perception subscale was associated with older age "p 9[92#[ Decline in speci_c cognitive domains may indicate
a reversible phase of cognitive impairment and deserves further investigation[ Copyright Þ 1999 John Wiley + Sons\
Ltd[
KEY WORDS*epidemiology^ longitudinal^ population!based cohort^ aged^ cognition^ neuropsychology^ CAMCOG:
CAMDEX
INTRODUCTION
Cognitive decline in {normal ageing| is becoming
an area of increasing interest due to the possibility
that it may represent a less severe but similar pro!
cess to that in dementia "Brayne and Calloway\
0877#[ In Alzheimer|s disease there is a sequential
decline across speci_c cognitive domains that
Correspondence to] S[ Cullum\ General Practice and Primary
Care Research Unit\ Institute of Public Health\ University For!
vie Site\ Robinson Way\ Cambridge CB1 1SR\ UK[ Tel:Fax]
¦33!0112!229299[ E!mail] sjc47Ýmedschl[cam[ac[uk
Contract:grant sponsor] Anglia and Oxford Regional NHS
R+D Health Services "SC#
Copyright Þ 1999 John Wiley + Sons\ Ltd[
re~ect the neuropathological changes in the
disease[ Almkvist and Baeckman "0882# described
an initial slow decline in episodic memory followed
by a more rapid decline in psychomotor speed\
semantic memory and visuospatial function[ To
accurately compare the cognitive decline in {nor!
mal ageing| with that seen in dementia\ we need
to investigate change within separate domains of
cognitive function\ using a su.ciently com!
prehensive and sensitive instrument[ Most studies
have applied neuropsychological test batteries to
either groups of healthy volunteers that may not
be representative of the non!demented elderly\ or
to entirely unselected population groups that may
have included individuals with dementia "Schaie\
Received 1 September 0888
Accepted 19 December 0888
743
S[ CULLUM ET AL[
0872^ Cornoni!Huntley et al[\ 0874^ Finch and Sch!
neider\ 0874#[ The population!based cohort studies
that have examined cognitive decline in non!
demented elderly populations are summarised in
Table 0[ Most of these have reported a decline
in global cognitive function as measured by brief
dementia screening instruments such as the Mini
Mental State Examination or MMSE "Folstein et
al[\ 0864#\ but have been unable to shed much
light upon domain!speci_c cognitive decline[ The
MMSE encompasses a number of di}erent
domains of cognitive function including orien!
tation\ attention\ and immediate and short!term
memory recall[ However\ the MMSE cannot be
used to measure domain!speci_c change\ because
most of the domains are represented by only one
or two items\ resulting in ~oor and ceiling e}ects
and insensitivity to change within each area of
cognitive function[
Very few population!based studies of cognitive
decline in normal ageing have used su.ciently sen!
sitive and broad!ranging tests of cognitive function
to enable investigation of change in di}erent cog!
nitive domains[ The aim of this study is to describe
the change and determinants of change in di}erent
domains of cognitive function in non!demented
subjects interviewed in a longitudinal population!
based study\ using a comprehensive measure of
cognitive function] the Cambridge Cognitive
Examination "CAMCOG#[ The CAMCOG forms
part of the Cambridge Mental Disorders of the
Elderly Examination "CAMDEX# "Roth et al[\
0875\ 0877\ 0888#[ It includes eight subscales that
assess di}erent cognitive domains] Orientation\
Language\ Memory\ Attention\ Calculation\
Praxis\ Abstract thought and Perception\ allowing
investigation of decline in di}erent cognitive
domains[ In contrast to the MMSE\ the CAM!
COG is a sensitive measure of cognitive function
and has little {ceiling e}ect| in the non!demented
elderly "Huppert et al[\ 0884#[
METHODS
The subjects
The Cambridge City Over!64 Cohort "CC64C#
is an on!going longitudinal study of a population
sample of elderly people living in Cambridge
"Brayne et al[\ 0886a#[ Fig[ 0 is a diagrammatic
representation of the whole study population and
the subsample selected for the study presented in
this paper "{CAMCOG subsample|#[
Copyright Þ 1999 John Wiley + Sons\ Ltd[
In 0874\ a prevalence survey of dementia was
carried out\ using the MMSE as a screening instru!
ment "O|Connor et al[\ 0878#[ The sample was
selected from six group general practice lists and
one in three from a seventh general practice list[
Two thousand six hundred and nine individuals
agreed to participate\ which constituted 39) of
the population of Cambridge aged 64 or over at
that time[ Those individuals who scored below 13
on the MMSE\ and one in three of those who
scored 13 or 14 were interviewed using the diag!
nostic interview schedule Cambridge Mental Dis!
orders of the Elderly Examination "CAMDEX#[
The non!demented survivors were re!screened with
the MMSE in the incidence wave carried out in
0877Ð0878 "Paykel et al[\ 0883#[ Those who scored
below 11\ all those whose score dropped by 3 or
more points\ those scoring 18 or 29 on both
occasions\ those over age 75 and a random strati!
_ed sample of those who scored 11 or above on the
MMSE were re!interviewed with the CAMDEX
schedule at two separate time points as part of an
intensive follow!up programme[
In the incidence wave of the study\ participants
from the _rst two general practices "the CAMCOG
subsample\ n 492# were o}ered the CAMCOG
examination instead of the MMSE at re!screening[
Of the participants who consented to use of the
CAMCOG\ 307 were able to complete the entire
test[ Of the CAMCOG subsample\ 122 were re!
interviewed after a mean time period of 2[8 years
and 054 of these completed the full CAMCOG[
Altogether\ 036 participants completed CAM!
COGs at the incidence wave and at follow!up[
Dementia was diagnosed using the CAMDEX in
01 of the 036 between the two interviews[ This
paper reports the decline in cognitive function in
the 024 subjects who had complete CAMCOGs at
both interviews and did not have dementia[
The interviews
All participants were interviewed in their own
home or other place of residence at the time of
interview[ Institutionalised subjects were also
included[ Trained lay interviewers administered the
screening interviews and regular quality control
meetings were held[ Inter!rater reliability has been
reported as satisfactory "Brayne et al[\ 0884#[ The
diagnostic interviews were carried out by psy!
chiatrists or by a nurse supervised by a psychiatrist[
Items that were not answered were coded accord!
ing to the reason for non!completion[ If physical
Int[ J[ Geriatr[ Psychiatry 04\ 742Ð751 "1999#
Copyright Þ 1999 John Wiley + Sons\ Ltd[
298
Age 73Ð89
433
Men
Age 69Ð78
0630
Age 64¦
0255
Age 54¦
254 women
Age 69¦
0024
Age 69¦
1463
Age 54¦
592
Age 69Ð77
676
Age 54Ð73
OCTO study
"Johannson et al[\ 0881#
Zutphen study
"Feskens et al[\ 0883#
CPLL
"Brayne et al[\ 0884#
MoVIES project
"Ganguli et al[\ 0885#
Soham study
"Brayne et al[\ 0886b#
Canberra
"Korten et al[\ 0886#
Bordeaux
"Jacqmin!Gadda et al[\ 0886#
Edinburgh
"Starr et al[\ 0886#
AMSTEL study
"Jonker et al[\ 0887#
394
318
0922
seen at 3 visits
503
126
0906
0000
267
082
Follow!up
sample size
predicted from model^ adjusted for age and education[
Baseline
sample size
Author
CAMCOG
MMSE
MMSE
MMSE
MMSE
CAMCOG
MMSE
CERAD
MMSE
MMSE
MMSE
Test used
2 years
3 years
0\ 2 + 4 years
2[5 years
4 years
1 years
1[3 years
2 years
1 years
Time
interval
Table 0[ Cognitive decline in normal ageing] population!based studies
−0[24:yr in apoE3 carriers "−9[8\ −0[7#
−9[3:yr in non!carriers "9[05\ −9[53#
−9[2
Age 54 −9[91:yr
Age 74 −9[4:yr
−9[4 "SD 1[9#
MMSE] −0[9 "−9[6\ −0[3#
CAMCOG] −3[6 "−2[3\ −4[8#
−9[60 "SD 1[0#
−0[2 "SE 9[98#
−9[7 in apoE3 carriers
−9[0 in non!carriers
"adjusted for age and education#
−0[8
Change in score for time interval
"SD\ SE or 84) CI if given#
Dementias at baseline and
during study excluded
Subjects with health
problems or taking
medications excluded
Dementias at baseline and
during study excluded\
institutionalised excluded
Dementias at baseline and
during study excluded
Dementias at baseline
excluded
Dementias at baseline
excluded
Dementias at baseline
excluded
Dementia not excluded
Dementia not excluded
Comments
DECLINE IN COGNITIVE FUNCTION IN NORMAL AGEING
744
Int[ J[ Geriatr[ Psychiatry 04\ 742Ð751 "1999#
745
S[ CULLUM ET AL[
Fig[ 0[ Diagrammatic representation of CC64C study and CAMCOG subsample
or sensory impairment "for example\ stroke or
blindness# prevented the individual from com!
pleting an item\ it was coded as not applicable[
Refusal to attempt an item\ {don|t know| answers
and nonsense answers were all coded separately[
As the interviews were conducted in the
community\ one item in the CAMCOG Perception
subscale "asking if the respondent recognises two
people in the room# was omitted\ thereby reducing
the total score from 096 to 095[
The CAMDEX schedule has been reported as
a valid and reliable diagnostic interview in this
population "O|Connor et al[\ 0880#\ and the
reliability of the individual CAMCOG subscales
has also been reported as acceptable "Huppert et
al[\ 0885#[
Statistical methods
Analyses were performed on the data from non!
demented subjects in the CAMCOG subsample
with complete CAMCOGs at both interviews[ Two
Copyright Þ 1999 John Wiley + Sons\ Ltd[
sample t!tests and chi!square tests were used to
compare the distributions of sociodemographic
characteristics and baseline scores of "i# the group
with complete CAMCOG data "n 024# and the
remainder of the CAMCOG subsample "n 66#
and "ii# the total CAMCOG subsample "n 101#
and the remainder of the CC64C study population
with no dementia seen at both time points
"n 242#[ Change in CAMCOG subscale score
was tested using paired t!tests and\ due to the
skewed distribution of change scores\ also with the
non!parametric equivalent of the paired t!test\ the
Wilcoxon matched!pairs signed!ranks test[ The
CAMCOG subscales have di}erent sensitivities to
change and therefore quantitative comparison of
change is not meaningful[ For this reason\ the data
for the CAMCOG subscales were dichotomised
into decline and no decline:improvement in score
and entered into a logistic regression model[ Age
at incidence wave was categorised into two age!
groups "64Ð68\ 79¦#\ educational level was cat!
egorised into school leaving age ³ 04 or 04 and
Int[ J[ Geriatr[ Psychiatry 04\ 742Ð751 "1999#
746
DECLINE IN COGNITIVE FUNCTION IN NORMAL AGEING
over^ social class was grouped into manual and
non!manual^ and total CAMCOG scores at the
incidence wave were grouped as 9Ð78\ 89Ð095[
Due to their brevity and the fact that they measure
similar aspects of cognitive function\ the Attention
and Calculation subscales were combined to form
one subscale[ All missing items were recoded to
zero for statistical analysis[ Statistical analysis was
performed using STATA\ version 4[9[
RESULTS
Of the 492 subjects seen in the CAMCOG sub!
sample at incidence wave\ 122 were re!assessed at
follow!up between 2[3 and 4 years later[ Of the 169
not seen\ 048 had died[ The remaining 000 were
refusals\ too ill to be interviewed or lost to follow!
up[
Representativeness of the sample
The distribution of age\ sex\ educational level\
social class and MMSE score of the CAMCOG
subsample at the incidence wave are shown in
Table 1[ There were no statistically signi_cant
di}erences in sociodemographic characteristics or
initial MMSE score between the group with full
CAMCOG data "n 024# and the rest of the
CAMCOG subsample with no dementia "n 66#[
There were also no signi_cant di}erences in the
distribution of sex\ educational level\ social class
and initial MMSE score between the total CAM!
COG subsample "n 101# and the remainder of
the study population without dementia at follow!
up "n 242#[ The mean age of the total CAMCOG
subsample at incidence wave "n 101# was
9[7 years younger than the remainder of the study
population who survived to be seen at the follow!
up survey "p ³ 9[90\ unpaired t!test#[
Table 1[ Distribution of sociodemographic characteristics and incidence wave MMSE scores in the CAMCOG
subsample
Percentage of
CAMCOG subsample
with complete data "n#
Percentage of the
rest of CAMCOG
subsample "n#
Percentage of
total CAMCOG
subsample "n#
Percentage of the
remainder of study
population at follow!up "n#
Age at incidence wave
64Ð68
79Ð73
74¦
32 "47#
33 "48#
02 "07#
34 "24#
32 "22#
01 "8#
33 "82#
32 "81#
02 "16#
24 "012#
32 "042#
11 "66#
Gender
Males
Females
16 "25#
62 "88#
16 "10#
62 "45#
16 "46#
62 "044#
23 "019#
55 "122#
School leaving age
³04 years
04¦ years
53 "75#
25 "38#
50 "36#
28 "29#
52 "022#
26 "68#
50 "104#
28 "027#
Social class
Manual
Non!manual
45 "64#
33 "59#
51 "37#
27 "18#
47 "012#
31 "78#
44 "085#
34 "046#
Age at incidence wave
Mean "SD#
70[4 "2[34#
70[1 "1[87#
70[3 "2[17#
71[1 "2[40#
MMSE score at incidence wave
Median "IQR#
Mean "SD#
16 "13\18#
15[0 "2[03#
16 "13\17#
14[7 "2[34#
16 "13\17#$
15[1 "2[99#$
16 "13\17#$
15[9 "1[75#$
p 9[994 "unpaired two!tailed t!test[
$
Only for participants with full data] 084:101 CAMCOG subsample and 205:242 rest of study population[
Copyright Þ 1999 John Wiley + Sons\ Ltd[
Int[ J[ Geriatr[ Psychiatry 04\ 742Ð751 "1999#
747
S[ CULLUM ET AL[
Table 2[ Change in the total CAMCOG score and CAMCOG subscale scores in the CAMCOG subsample "n 024#
Score at incidence wave
Median "IQR#
Mean "SD#
Follow!up score
Median "IQR#
Mean "SD#
Di}erence
Median "IQR#
Mean "84) CI#
Total CAMCOG
max score 095
78 "72\84#
76[6 "8[11#
74 "63\81#
70[6 "03[2#
−2 "−01\9#
−5[9 "−6[5\−3[3#
Orientation
max score 09
09 "8\09#
8[3 "9[71#
8 "7\09#
7[7 "0[46#
9 "−0\0#
−9[5 "−9[8\−9[3#
Language
max score 29
15 "13\16#
14[3 "1[30#
14 "12\16#
13[3 "2[10#
−0 "−1\0#
−0[9 "−0[4\−9[4#
Memory
max score 16
11 "10\12#
10[6 "1[73#
11 "08\12#
19[1 "3[62#
−0 "−2\0#
−0[4 "−1[0\−9[8#
7 "5\8#
6[2 "0[71#
6 "4\7#
5[4 "1[13#
−0 "−1\9#
−9[7 "−0[0\−9[4#
00 "09\01#
09[4 "0[44#
09 "7\00#
8[5 "1[08#
9 "−1\0#
−9[7 "−0[1\−9[4#
5 "3\6#
4[3 "1[28#
5 "2\6#
3[8 "1[45#
9 "−0\0#
−9[4 "−9[8\−9[0#
7 "5\8#
6[2 "1[95#
9 "−1\9#
−9[6 "−0[9\ −9[3#
Attention!calcualtion
max score 8
Praxis
max score 01
Abstract thought
max score 7
Perception
max score 09
7 "6\8#
7[9 "0[43#
p ³ 9[94^ p ³ 9[990 "paired two!tailed t!tests on means of samples#[
Chan`e in total CAMCOG and CAMCOG subscale
scores
The total CAMCOG and CAMCOG subscale
scores at both interviews are summarised in Table
2[ Total CAMCOG score declined by a mean of 5
points "p ³ 9[990#[ The mean annual rate of
change in CAMCOG was −0[5 points per year
"84) CI−1[9\ −0[0#[ The distribution of the
annual rate of change in total CAMCOG score is
shown in Fig[ 1[
The mean decline in the CAMCOG subscales
varied from −9[4 points in Abstract thought to
−0[4 points in Memory[ All mean declines in the
CAMCOG subscale scores were statistically sig!
ni_cant[ On non!parametric statistical analysis\ the
declines in the total CAMCOG and the CAMCOG
subscales remained signi_cant at p ³ 9[990 except
for decline in Abstract thought "p 9[91#[
Effect of sociodemo`raphic variables and baseline
score on decline in the CAMCOG subscale scores
Table 3 shows the number of participants with
decline or no decline for each CAMCOG subscale
categorised by age\ sex\ education\ social class\ and
baseline total CAMCOG score[ Greater decline
Copyright Þ 1999 John Wiley + Sons\ Ltd[
in the Memory subscale was associated with less
education "p 9[92#[ Greater decline in the Atten!
tion:Calculation subscale was associated with
manual social class "p 9[94#[ Greater decline in
the Perception subscale was associated with older
age "p 9[92#[
DISCUSSION
Mean _ndin`s
The main _ndings of this study were that the
mean decline in total CAMCOG score over
approximately 3 years was 5 points[ There was
also signi_cant decline in all of the CAMCOG
subscales[ Decline in the Memory subscale was
associated with less education\ decline in the Atten!
tion:Calculation subscale was associated with
lower social class and decline in the Perception
subscale was associated with older age[
Comparison with previous _ndin`s
The mean decline in total CAMCOG score was
consistent with the decline of 3[6 points over 4
years reported by Brayne et al[ "0886b#\ and with
Int[ J[ Geriatr[ Psychiatry 04\ 742Ð751 "1999#
DECLINE IN COGNITIVE FUNCTION IN NORMAL AGEING
748
Fig[ 1[ The distribution of the annual rate of change in CAMCOG scores in the CAMCOG subsample with full CAMCOG data
"n 024#
that found by Jonker et al[ "0887# who reported
an annual decline of 0[3 points in apoE3 carriers
and 9[3 points in non!carriers[ The latter study
also reported decline in both the memory and non!
memory subscales of the CAMCOG\ which is in
accordance with our _ndings of signi_cant decline
in all of the CAMCOG subscales[ Very few popu!
lation!based studies have examined the e}ect of
sociodemographic characteristics on decline in
speci_c domains of cognitive function in the non!
demented elderly[ Korten et al[ "0886# reported
that memory decline was associated with older age
and lower baseline score[ The present study found
that decline in the Memory subscale was associated
with less education\ but not with older age or lower
baseline score[
Stren`ths and weaknesses
One explanation for the decline in some of the
CAMCOG subscales might be due to the high
number of individuals scoring the maximum score
at baseline in some of the subscales "Orientation\
Attention:Calculation and Praxis#[ As it is imposs!
ible to measure random improvement for those
individuals at the top of the scale\ the phenomenon
of regression to the mean may have created the
spurious impression of decline in these subscales
Copyright Þ 1999 John Wiley + Sons\ Ltd[
"Morris et al[\ 0888#[ Conversely\ the ceiling e}ect
could also have masked greater decline in high
functioning individuals at baseline\ which would
have concealed the full extent of cognitive decline
in some of the subscales[
An important question is whether the reported
decline was entirely due to the e}ect of a small
subgroup with early dementia or some other cause
of cognitive impairment[ As the CC64C study was
unable to conduct another wave of diagnostic
interviews\ it is di.cult to judge whether the
decline was in fact prodromal of dementia[
However\ if the results were due to a subgroup
with an early dementing process\ we might expect
to see decline in the memory subscale more com!
monly than in the other subscales\ but this was not
the case[ In fact\ over 49) of the sample showed
decline in at least three areas of cognitive function
and only seven of the 024 study participants
showed no decline in any of the CAMCOG subs!
cales[ Even if decline were rede_ned as a drop of
at least 1 points in each subscale\ 24) of the
sample still showed decline in at least three areas
of cognitive function[ It is unlikely that these
results were solely due to early dementia\ which
suggests that cognitive decline across a range of
cognitive domains is relatively common in normal
ageing[ However\ the decline may still be due to
Int[ J[ Geriatr[ Psychiatry 04\ 742Ð751 "1999#
Copyright Þ 1999 John Wiley + Sons\ Ltd[
×04 yrs
04¦ yrs
OR
OR adj
Manual
Non!
man
OR
OR adj
Age left
school
Social
class
27
27
20
26
16
39
0[13 "9[51Ð1[35#
0[49 "9[63Ð2[91#
22
11
31
33
05
22
0[86 "9[84Ð3[98#
Lang
no decl
24
15
25
21
25
20
9[86 "9[38Ð0[89#
9[68 "9[28Ð0[46#
25
23
34
30
16
11
9[78 "9[33Ð0[79#
43
34
07
07
0[19 "9[45Ð1[47#
31
24
29
17
0[01 "9[46Ð1[11#
Lang
decline
Memry
no decl
29
14
33
13
23
22
0[67 "9[78Ð2[44#
9[87 "9[38Ð0[85#
30
24
46
18
10
17
1[51 "0[16Ð4[28#
1[27 "0[96Ð4[21#
adj for baseline score
48
39
08
06
0[21 "9[50Ð1[73#
34
21
22
14
0[96 "9[42Ð1[01#
Memry
decline
Att:cal
no decl
16
23
28
18
21
24
0[36 "9[76Ð2[34#
1[02 "0[95Ð3[18#
1[99 "9[87Ð3[97#
adj for base score
1[00 "0[93Ð3[17#
adj for age
33
15
37
27
12
15
0[32 "9[60Ð1[78#
40
37
19
05
9[74 "9[28Ð0[72#
34
32
15
21
0[62 "9[76Ð2[33#
Att:cal
decline
Praxis
no decl
26
18
22
24
22
23
9[86 "9[38Ð0[80#
9[75 "9[32Ð0[60#
23
20
39
37
15
12
9[66 "9[27Ð0[44#
41
36
03
11
0[63 "9[79Ð2[67#
28
27
16
20
0[06 "9[59Ð1[22#
Praxis
decline
Abstra
no decl
27
26
16
30
20
25
9[65 "9[28Ð0[40#
0[39 "9[58Ð1[70#
22
12
27
37
19
18
0[04 "9[45Ð1[23#
33
44
03
11
0[15 "9[47Ð1[63#
29
36
17
29
9[57 "9[23Ð0[25#
Abstr
decline
Percep
no decl
25
29
21
25
24
21
9[70 "9[30−0[59#
9[86 "9[38Ð0[82
24
29
35
39
10
17
0[42 "9[65Ð2[00#
37
40
08
06
9[73 "9[28Ð0[70#
33
22
12
24
1[92 "0[90Ð3[95#
0[86 "9[87Ð2[85#
adj for education
Percep
decline
OR adjusted for one other variable if lower limit of 84) CI × 0\ adjusted for other variable only due to small numbers in cells[
Key] Orient] Orientation^ Lang] Language^ Memry] Memory^ Att:cal] Attention:Calculation^ Praxis] Praxis^ Abstr] Abstract thought^ Percep] Perception^ no decl] no decline
in subscale[
Baseline
³89
CAMCOG 89Ð095
score
OR
OR adj
Female
Male
OR
OR adj
Sex
35
42
01
13
0[63 "9[67Ð2[74#
20
35
16
20
9[66 "9[28Ð0[43#
×79
64Ð68
OR
OR adj
Age
Orient
no decl
Orient
decline
Sociodemographic
characteristics
Table 3[ Odds of decline in CAMCOG subscales by sociodemographic characteristics "n 024#
759
S[ CULLUM ET AL[
Int[ J[ Geriatr[ Psychiatry 04\ 742Ð751 "1999#
DECLINE IN COGNITIVE FUNCTION IN NORMAL AGEING
identi_able subgroups[ The prevalence of {cog!
nitive impairment\ no dementia| "CIND# in this
study\ de_ned by a total CAMCOG score below
79 at baseline\ was 02)[ This _gure compares with
05[7) reported by the Canadian Study of Health
and Ageing "Graham et al[\ 0886#[ Cognitive
decline in the CIND subgroup was higher
"p 9[90\ ANOVA adjusted for age#\ but was not
completely responsible for the observed results\ as
the fall in CAMCOG still remained highly sig!
ni_cant for the rest of the sample[ Some of the
study participants may have ful_lled criteria for
non!progressive cognitive decline[ Ageing!associ!
ated cognitive decline "AACD# requires evidence
of decline in one or more of a broad range of
cognitive domains\ and has a prevalence of 16)
in the 57Ð67 age group "Hanninen et al[\ 0885#[
Others may have met the criteria for age!associated
memory impairment "AAMI#\ which has been
shown to be clinically distinct from AACD "Rich!
ards et al[\ 0888#[ There are various ways to classify
cognitive decline in normal ageing and the under!
lying causes are equally diverse[ The majority of
participants in this study were likely to have had
risk factors that were related to cognitive impair!
ment and dementia\ such as hypertension[ It has
been argued that cognitive decline in elderly indi!
viduals with physical pathologies may be disease!
related and not representative of cognitive decline
in {normal ageing| at all "Starr et al[\ 0886#[ Then
again\ these risk factors are so common in old age
that a sample de_ned by absence of disease might
be considered to be {supernormal| "Petersen et al[\
0886#\ and would not show the characteristics of
{typical ageing|[
The sample size in this report was relatively
small for an epidemiological study\ and may not
have been large enough to detect an association
between baseline factors and decline in cognitive
function in the CAMCOG subscales[ Even so\
decline in three of the subscales was associated
with speci_c sociodemographic features\ albeit at
a low level of statistical signi_cance[ Studies that
have investigated the sociodemographic deter!
minants of decline in `lobal cognitive function\ as
measured by the MMSE\ have reported associ!
ations with older age "Brayne et al[\ 0884^ Ganguli
et al[\ 0885^ Jacqmin!Gadda et al[\ 0886^ Korten
et al[\ 0886#\ less education "Farmer et al[\ 0884^
Ganguli et al[\ 0885^ Jacqmin!Gadda et al[\ 0886#\
lower baseline score "Korten et al[\ 0886# and
female sex "Brayne et al[\ 0884#[ It is possible that
the e}ects of age\ sex\ education\ social class and
Copyright Þ 1999 John Wiley + Sons\ Ltd[
750
baseline score on cognitive decline are not the same
in the di}erent domains of cognition\ but that these
e}ects are masked when only global measures of
cognition are reported[ This hypothesis would
explain the results of the current study\ but does
not explain why factors that are highly correlated
such as social class and education do not show
similar associations with decline in the separate
subscales[ In view of the small sample size and
the multiple analyses\ these results may be in part
attributable to statistical artefact "type I error#[
CONCLUSION
There is substantial research interest in di}er!
entiating progressive and non!progressive cog!
nitive decline in the elderly[ The important _nding
from this study is that the mean scores for each of
the CAMCOG subscales in this population have
declined over time[ In addition\ the majority of
study participants showed evidence of decline in at
least three of the cognitive domains measured by
the CAMCOG subscales[ If the results of epi!
demiological and intervention studies investigating
cognitive decline in normal ageing are to be mean!
ingful\ the outcomes should be measured using
instruments such as the CAMCOG that are sen!
sitive to change across a range of domains of cog!
nitive function[
ACKNOWLEDGEMENTS
Sarah Cullum was funded by an Anglia and
Oxford Regional NHS R+D Health Services
Research Training Fellowship[ The Cambridge
City Over!64 Cohort has received support from
the Charles Wolfson Trust\ MRC\ NHS R+D\
the Edward Storey Foundation and Research into
Ageing[
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