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International Psychogeriatrics (2005), 17:2, 289–301 C
2005 International Psychogeriatric Association
doi:10.1017/S1041610205001511 Printed in the United Kingdom
Differential cognitive impairment in subjects
with geriatric depression who will develop
Alzheimer’s disease and other dementias:
a retrospective study
..............................................................................................................................................................................................................................................................................
Le
’onie Jean,1Martine Simard,1,2 Robert van Reekum3
and Diana E. Clarke4
1´
Ecole de psychologie, Universit´
e Laval, Centre de Recherche Universit´
e Laval-Robert-Giffard,
Qu´
ebec City, Canada
2´
Ecole de psychologie, Universit´
e de Moncton, Moncton, Canada
3Department of Psychiatry and Kunin-Lunenfeld Applied Research Unit, Baycrest Centre for Geriatric Care,
and Division of Geriatric Psychiatry, University of Toronto, Toronto, Canada
4Graduate Department of Public Health Sciences and the Collaborative Program in Aging and the Life Course,
University of Toronto, and Department of Psychiatry, Baycrest Centre for Geriatric Care, Toronto, Canada
ABSTRACT
Objective: The aim of this study was to retrospectively differentiate the cognitive
profile of subjects with geriatric depression who will later be diagnosed
with Alzheimer’s disease (AD) from those who will be diagnosed with other
dementias, and subjects who will remain with no dementia.
Methods: Forty-four depressed patients admitted to a day hospital program
for depression who participated in a historical cohort study were assessed
after 7.5 years of follow-up. Fourteen of these subjects subsequently developed
dementia: seven met the criteria for probable AD and seven met the criteria for
dementias other than AD (Dementia-No-AD; D-NAD, such as dementia with
Lewy bodies (DLB), vascular and mixed dementia). Thirty subjects remained
without dementia (No Dementia, ND) at follow-up. The three groups were
thus compared on their baseline cognitive performances on the six sections of
the Mini-mental State Examination (MMSE) and on the five subscales of the
Dementia Rating Scale (DRS).
Results: An analysis of variance (ANOVA) and post-hoc Student–Newman–
Keuls analyses with an alpha of p<0.05 revealed that the subjects who received
a diagnosis of dementia at follow-up had previously had more impairment on
tasks measuring attention and memory (DRS-MMSE) than those who did not
Correspondence should be addressed to:L
´
eonie Jean, ´
Ecole de psychologie, Pavillon F´
elix-Antoine-Savard, Universit´
e
Laval, Quebec City, Quebec G1K 7P4, Canada. Phone +1 418 656 2131 ext. 11104; Fax: +1 418 6563646.
Email: Leonie.Jean.1ulaval.ca Received 11 Feb 2004; returned for revision 23 Mar 2004; revised version received 8
Apr 2004; accepted 19 Apr 2004.
289
290 L. Jean et al.
develop dementia (AD =D-NAD <ND). Moreover, the future AD subjects
could be differentiated on the basis of their difficulties on the MMSE-orientation
subtest (AD <ND =D-NAD), whereas the future D-NAD subjects initially had
more problems with executive functions (DRS) and MMSE-visuospatial abilities
(D-NAD <AD =ND).
Conclusion: The identification of early neuropsychological markers in elderly
depressed patients highlights the need to evaluate this population broadly as
soon as possible in the depression/dementia process in order to improve the
prognosis.
Key words: Neurodegenerative disorders, prodromal phase, early diagnosis, cognition, attention, memory,
MMSE
Introduction
Cognitive impairment associated with geriatric depression is a major concern
because of the potential impact on the functional ability of the elderly individual
(Kiosses et al., 2000), and because such impairments may limit pharmacological
treatment response (Kalayam and Alexopoulos, 1999). The severity of the
depressive illness seems to be associated with cognitive dysfunction (Elderkin-
Thompson et al., 2003), particularly in those elderly patients with central nervous
system disease (van Reekum et al., 2000).
Problems with executive functions (Alexopoulos et al., 1997) and working
(Nebes et al., 2000) and episodic memory (B ¨
ackman and Forsell, 1994)
are commonly observed in geriatric patients with symptoms of depression.
Thus depressed elderly people frequently present difficulties with organizing
and initiating activities, and have problems using efficacious strategies to
learn and recall information (Alexopoulos, 2001). These alterations have been
hypothesized to be related to an impairment of the frontostriatal pathways
during, and probably after, the depressive episode (Royall, 1999).
Cognitive deficits are often present during the episode of geriatric depression
and after the remission of depression (Alexopoulos et al., 1993), even when
the mood disorder has responded efficaciously to antidepressant medications
(Nebes et al., 2003). Moreover, recent studies suggested that geriatric
depression represents a prodromal phase of dementia (van Reekum et al.,
1999). Some authors have reported that 9–43% of elderly people who have
depression subsequently develop some kind of dementia (Alexopoulos et al.,
1993; Halloran et al., 1999; Stek et al., 2002).
However, few studies have examined cognitive markers, in terms of
neuropsychological impairment, that can predict the future development of
specific types of dementia, and differentiate the profile of future Alzheimer’s
disease (AD) from that of other future dementias, in patients with geriatric
Cognitive impairment in geriatric depression 291
depression. Alexopoulos et al. (1993) found that no clinical and cognitive
characteristics at entry into their study could discriminate the individuals
who developed dementia at the 3-year follow-up from those who remained
without dementia. In another longitudinal study (Halloran et al., 1999), the
results of several neuropsychological tests did not predict clinical or cognitive
outcome. However, a low Mini-mental State Examination (MMSE) score at
index assessment predicted dementia at follow-up 2 years later. Subjects who
developed dementia obtained an index MMSE score of 20.2 compared with a
score of 25.9 in those who did not develop dementia (Halloran et al., 1999).
However, Halloran and her collaborators did not specify the types of dementia
that were diagnosed in their subjects.
Because at least some of the dementias may be prevented, it is highly
important to specify cognitive markers as soon as possible in the dementia
process. The goal of the present study was to retrospectively differentiate the
cognitive profile of subjects with geriatric depression who were later diagnosed
with AD from those subjects who were diagnosed with other dementias,
and subjects who remained without dementia. Consequently, the present
study retrospectively investigated the cognitive profile of elderly subjects with
depression at their first admission and discharge to a day hospital for depression,
and who were diagnosed a mean of approximately 7.5 years later (at long-term
follow-up) with AD, other dementias and no dementia.
Subjects
A detailed description of the source of subjects, sampling procedure and sample
characteristics has been provided previously (van Reekum et al., 1999). Briefly,
subjects were patients of a geriatric day hospital for depression who, at baseline,
met the criteria for major depression (as assessed by the attending psychiatrist
according to the DSM manuals appropriate to the time interval) and who did not
suffer from neurodegenerative dementia or other central nervous system disease
or injury at their admission into the day hospital for depression. In addition, the
assessment at admission to the day hospital for depression (our baseline data) was
made by the same clinical team over the years, using the same instruments. This
process should have maintained homogeneity and standardization in application
of the clinical criteria. Clinical data at admission and discharge into the program
have been collected systematically for more than 10 years, and coded onto a
computerized database. This database provided the retrospective baseline data
for the present study.
Three hundred and thirty-one subjects in the database had a diagnosis of
major depression. Two hundred and sixty-four subjects remained after excluding
292 L. Jean et al.
those with a history of dementia (as diagnosed by the admitting psychiatrist
according to the DSM manuals appropriate to the time interval) or other central
nervous system disease, and this number was decreased to 245 subjects for whom
age of onset of the first episode of depression was available. The final selection
criterion was the presence of cognitive testing (performed routinely at admission
into the day hospital) with the Dementia Rating Scale (DRS; Mattis, 1976); all
191 subjects thus identified were eligible for inclusion in the initial study (van
Reekum et al., 1999).
The present study uses the dementia diagnoses obtained in a historical cohort
follow-up study of the original sample (van Reekum et al., 2005). In brief, the
duration of follow-up was the period of time from the date of entry into the
day hospital to the date of enrollment into the follow-up study. Subjects and/or
their substitute decision makers were contacted by letter, and then by follow-
up phone call to discuss the details of the study. The outcomes of interest
were the diagnosis of AD according to the DSM-IV and NINCDS-ADRDA
(National Institute of Neurological and Communicative Disorders and Stroke –
the Alzheimer’s Disease and Related Disorders Association) criteria, vascular
dementia, ischemic vascular dementia, dementia with Lewy bodies (DLB) and
frontotemporal dementia (FTD). The assignment of diagnosis was made by a
committee of the study’s investigators who independently reviewed collated data
on each subject. Each subject’s committee was composed of a neurologist, a
psychiatrist and a neuropsychologist. To meet the study’s criteria for one of the
dementias, the final assigned diagnosis had to be agreed upon by at least two
members of the committee.
At follow-up of the historical cohort, available and consenting individuals
were asked to undergo a neurological history and examination and cognitive
testing using the DRS (Mattis, 1973; 1976), the Western Aphasia Battery
(Kertesz, 1982) and the MMSE (Folstein et al., 1975). Metabolic screening and
a computed tomography (CT) scan were obtained for those who demonstrated
cognitive impairment on the DRS, unless the subject had previously had
these examinations (subsequent to the onset of their cognitive impairment).
A knowledgeable informant was interviewed with a semi-structured interview
(Sano et al., 1995). Baycrest Centre records (excluding day hospital records),
family physician records, and any neurological, psychiatric or geriatric medicine
assessment records were also obtained when available.
Agreements for participation in the historical cohort study were obtained
for 44 of the 191 eligible subjects. The group was therefore assessed after a
mean follow-up period of 7.5 years, with a standard deviation of 2.84 years
(range 3.4–12.7 years). The reasons for non-participation at follow-up included:
refusal to participate, inability to contact subjects, and illness in other subjects.
The important rate of loss at follow-up may thus reflect the frailty of this
Cognitive impairment in geriatric depression 293
particular population. Fourteen of the 44 subjects with geriatric depression
developed dementia (the follow-up MMSE mean score of surviving patients was
19; SD =6.44). Seven subjects met the NINCDS/ADRDA (McKhann et al.,
1984) and/or DSM-IV (American Psychiatric Association, 1994) criteria for
probable AD, and seven subjects met the criteria for other dementias: two
subjects met the Consortium on Dementia with Lewy Bodies (CDLB) criteria
(McKeith et al., 1996) for probable or possible DLB, two subjects met the
NINDS-AIREN (Rom´
an et al., 1993) and/or Alzheimer’s Disease Diagnostic
and Treatment Center (ADDTC) criteria (Chui et al., 1992) for vascular (VaD)
or ischemic vascular (IVaD) dementia and three subjects had mixed dementia.
The seven subjects who met the criteria for dementias other than AD were
amalgamated into a group termed “Dementia-but No AD” (D-NAD). Thirty
subjects had no dementia (ND); their mean MMSE follow-up score was 27.82
with a standard deviation of 2.13.
Ethical considerations
The study was approved by the Ethics Review Committee of Baycrest Centre.
Subjects and/or their substitute consent givers were fully informed about the
study, and the risks of participating in it. They signed an informed consent form
that had been approved by the Ethics Committee. All data that potentially could
identify a subject were kept strictly confidential by coding of study documents.
Methods
This was a retrospective neuropsychological study with between-diagnostic
group comparisons. The retrospective (baseline) data for these subjects obtained
at admission to the day hospital for depression included sex, level of education,
depression severity as assessed by the Hamilton Depression Rating Scale
(HDRS; Hamilton, 1960) at admission and discharge from the program as well
as cognitive functioning as assessed by the MMSE at admission and discharge
from the program, and the DRS at admission to the program. Statistical analyses
were performed on the subtests of the MMSE and DRS obtained at admission
into the day hospital.
Cognitive tests
The MMSE (Folstein et al., 1975) is a cognitive instrument that is short and easy
to administer. It is divided into six sections: spatial and temporal Orientation
(maximum score =10); Registration (maximum score =3); Recall (maximum
score =3); Attention/Calculation (maximum score =5); Language (maximum
294 L. Jean et al.
Table 1. Demographic and clinical characteristics of the subjects
AD N=7D-NAD N=7ND N=30
...........................................................................................................................................................................................................................................
Mean age (SD) at follow-up 78.00 (4.44) 79.71 (1.60) 73.27 (6.74)
Male/female 2/5 3/4 10/20
No education 0 0 1
Elementary school (partial) 5 2 3
Elementary school (completed) 1 1 3
High school (partial) 1 2 6
High school (completed) 0 1 12
College (partial or completed) 0 0 2
University (partial or completed) 0 1 3
Mean HDRS (SD) at admission 19.86 (6.17) 19.79 (3.63) 18.62 (5.66)
to program
Mean HDRS (SD) at discharge 7.60 (5.13) 8.60 (5.03) 7.57 (4.73)
from program
score =8); and Construction (maximum score =1). The maximum possible
total score is 30.
The DRS (Mattis, 1973; 1976) contains five subscales: Attention (maximum
score =37); Initiation/Perseveration (maximum score=37); Construction
(maximum score =6); Conceptualization (maximum score =39); and Memory
(maximum score =25). The total maximum score is 144.
Statistical analyses
Descriptive statistics (means and standard deviations) were used to describe the
subjects’ characteristics and results on the tests. The six subscores of the MMSE
and the five subscores of the DRS obtained at admission to the day hospital by the
subjects later diagnosed with AD, D-NAD and ND at follow-up were compared
using an analysis of variance (ANOVA) and post hoc Student–Newman–Keuls
analyses. An αof p<0.05 was applied to the variables.
Results
Table 1 presents the demographic and clinical characteristics of the subjects.
Pearson’s χ2-tests were performed between the AD, D-NAD and ND groups
on the gender and the level of education, whereas a one-way ANOVA was
performed on the age and the Hamilton total score at admission and discharge.
These analyses showed no significant difference between the three groups on
gender, education and Hamilton scores (admission and discharge). The ANOVA
demonstrated a significant difference on age (F=4.359, d.f . =2,41, p=0.019);
however, this difference was not found to be statistically significant by post hoc
Student–Newman–Keuls analyses with an α=0.05.
Cognitive impairment in geriatric depression 295
Table 2. Means and standard deviations on the MMSE and DRS
AD N=7D-NAD N=7ND N=30
.............................................................................................................................................................................................................................................
MMSE at admission to program – 23.14 (2.80) 23.86 (3.13) 28.30 (1.39)
total score
MMSE-Orientation (admission) 8.43 (1.27) 9.29 (0.49) 9.83 (0.38)
MMSE-Registration (admission) 2.86 (0.38) 3.00 (0.00) 3.00 (0.00)
MMSE-Attention/Calculation 3.00 (1.83) 2.29 (1.98) 4.73 (0.52)
(admission)
MMSE-Recall (admission) 1.14 (0.90) 2.00 (1.16) 2.30 (0.88)
MMSE-Language (admission) 6.86 (0.90) 7.00 (0.82) 7.57 (0.68)
MMSE-Construction (admission) 0.86 (0.38) 0.29 (0.49) 0.87 (0.35)
MMSE at discharge from program – 23.50 (1.73) 27.75 (1.89) 28.89 (1.10)
total score
DRS at admission – total score 119.86 (11.22) 113.71 (16.01) 133.23 (7.92)
DRS-Attention (admission) 33.86 (1.68) 33.14 (2.61) 35.47 (1.43)
DRS-Initiation/perseveration 28.14 (4.26) 29.00 (7.75) 33.40 (4.09)
(admission)
DRS-Construction (admission) 5.29 (1.50) 4.86 (1.95) 5.70 (0.70)
DRS-Conceptualization 34.71 (4.96) 29.14 (3.98) 36.40 (3.26)
(admission)
DRS-Memory (admission) 17.86 (4.10) 17.57 (3.95) 22.27 (2.84)
Table 2 presents the means and standard deviations obtained by the three
groups of subjects on the MMSE at admission and discharge, and on the
DRS at admission. A one-way ANOVA was performed between the AD,
D-NAD and ND groups on the six measures of the MMSE and the five
measures of the DRS obtained at admission in the day hospital for depression
program. This ANOVA showed a significant difference between the three
groups of patients on MMSE-Orientation (F=15.624, d.f . =2,41, p=0.000);
MMSE-Attention/Calculation (F=17.385, d.f. =2,41, p=0.000); MMSE-
Construction (F=7.038, d.f. =2,41, p=0.002); MMSE-Recall (F=4.454,
d.f. =2,41, p=0.018), MMSE-Language (F=3.651, d.f . =2,41, p=0.035);
DRS-Conceptualization (F=11.173, d.f. =2,41, p=0.000); DRS-Memory
(F=9.479, d.f . =2,41, p=0.000); DRS-Attention (F=6.771, d.f. =2,41,
p=0.003); and DRS-Initiation/Perseveration (F=4.837, d.f. =2,41, p=0.013)
subtests.
Post-hoc Student–Newman–Keuls analyses with an α=0.05 showed that
subjects with geriatric depression later diagnosed with AD were significantly
impaired on the MMSE-Orientation subtest when compared with subjects who
did not develop dementia and subjects later diagnosed with other dementias
(AD <ND =D-NAD). The subjects with AD also had a significantly inferior
performance on the MMSE-Recall subtest when compared with the subjects
with no dementia; however, their performance was comparable to that of
296 L. Jean et al.
subjects with other dementias (AD <ND; AD =D-NAD; D-NAD =ND).
The two groups later diagnosed with dementia (AD and D-NAD) had signi-
ficantly inferior performances on MMSE-Attention/Calculation, DRS-Attention
and DRS-Memory subtests when compared with the subjects who did not
develop dementia (AD =D-NAD <ND). The patients later diagnosed with
other dementias (D-NAD) were more significantly impaired than the other
subject groups on MMSE-Construction and DRS-Conceptualization subtests
(D-NAD <AD =ND).
To verify how representative our sample was, independent sample t-tests
with an α=0.05 were performed on the MMSE subtests at admission, the
MMSE global score at discharge, and the DRS subtests at admission between
the followed-up subjects (N=44) and those lost at follow-up (N=147). These
analyses showed no significant difference between the two groups on the MMSE
at both times. However, the patients lost at follow-up were more significantly
impaired on the DRS-Conceptualization subtest compared with the followed-up
subjects (t=2.646, d.f. =1,189, p=0.009) at baseline.
Discussion
The results of this study demonstrated that some differential cognitive
impairment exists in subjects with geriatric depression who later develop AD,
subjects who develop other dementias (such as DLB, vascular and mixed
dementia), and subjects who do not develop dementia. Only subjects who
received a diagnosis of dementia 7.5 years later had significant impairment on
attention and memory tasks. Furthermore, elderly adults with depression who
developed AD could be differentiated on the basis of their poor performance
on measures of orientation, attention and memory, whereas subjects who later
developed other types of dementia presented problems with executive functions
(abstraction and categorization), visuospatial abilities, attention and memory.
Thus, in contrast to the two previous studies (Alexopoulos et al., 1993; Halloran
et al., 1999), the present research suggests that there are some differential
neuropsychological predictors of dementia among elderly depressed people, and
these markers are more specific than only a low MMSE total score as proposed
by Halloran et al. (1999).
Some results of the current study, however, corroborated those obtained
in previous studies. Other authors have indeed reported that elderly people
with depression presented with difficulties in attention, memory and executive
functions (Alexopoulos et al., 1997; Nebes et al., 2003). At the end of the 7.5-
year follow-up, 31.8% (14/44) of the subjects of the present study had a cognitive
deterioration severe enough to meet the diagnostic criteria for dementia. This
Cognitive impairment in geriatric depression 297
result tends to confirm the hypothesis that a high percentage of depressed
elderly adults will subsequently evolve towards the cognitive profile of dementia
(Alexopoulos et al., 1997). Furthermore, our data tend to corroborate those of
the Canadian Study of Health and Aging regarding the high risk of dementia
in older females with a low education (Canadian Study of Health and Aging
Working Group, 1994). Table 1 shows that the AD and D-NAD subjects were
older, less educated and predominantly female, when compared with the ND
subjects, although these differences were not statistically significant.
Regarding the cognitive profile of individuals with AD, it is well documented
that orientation is among the first abilities to deteriorate in that population
(Ashford et al., 1989). In addition, memory problems are usually the most
severe cognitive impairment at onset of this disease (Palmer et al., 2003). It
was interesting to find these cognitive alterations in the present study in elderly
depressed subjects who may have been in the prodromal phase of AD. The
current research has also described alterations in attention, memory, visuospatial
and executive functions in depressed subjects who evolve towards other types of
dementia. This means that the cognitive deficits often reported in DLB (Simard
et al., 2000), VaD (Looi and Sachder, 1999) and IVaD (Tierney et al., 2001)
are also present in the prodromal phase of their respective dementia process.
These important findings have implications for the prevention, early diagnosis
and treatment of neurodegenerative dementias.
The present study, however, has some limitations. First, the small sample
sizes could result in a lack of statistical power. As our results are preliminary,
replication of the study with a larger number of subjects will represent an
interesting possibility for future research. Although the missing follow-up data
were a limitation of the study, our analyses have shown that our results,
despite being limited to 44 subjects, are representative of the 191 initial eligible
subjects to study. Thus, in terms of the MMSE scores, both follow-up patients
and patients lost at follow-up were similar at admission and discharge to the
program (at baseline). Those results suggest that both groups benefited from
the depression treatment. We can therefore rely on the data provided by the
44 follow-up patients; although they were slightly less impaired than the lost
at follow-up subjects on a sensitive measure of executive functioning (DRS-
Conceptualization).
It can also be argued that the initial MMSE score of those who subsequently
had dementia was a mean of <24, which might indicate that many of the subjects
had dementia at the start of the study, rather than developing dementia during
the 7.5-year follow-up. However, the widely used MMSE cutoff score of <24
for dementia is not corrected for age and education level. According to the cutoff
scores adjusted for age and level of education and calculated from the normative
data of Crum et al. (1993), the AD and D-NAD subjects were cognitively
298 L. Jean et al.
impaired but did not have dementia at the time of their initial admission into
the day hospital for depression (cut-off score for dementia was 22.4 for their
particular age and level of education group). Moreover, the main purpose of the
intensive assessment at admission to the day hospital was to ensure that potential
patients would probably be able to tolerate, and benefit from, the intensive (four
full days a week) program of psychotherapies of different types (along with other
types of therapy such as recreational therapy). Patients with dementia had been
found previously to be unable to tolerate the cognitively challenging aspect of the
program because of difficulties with fatigue, agitation, and so on, and were not
able to generate much in the way of new learning related to the psychotherapies.
As such, patients with signs of dementia that were of any clinical concern were
excluded from the day hospital (and hence would not have appeared in the
database).
In addition, there was an absence of neuropathological confirmation of the
AD, DLB and VaD diagnoses. However, the NINCDS-ADRDA criteria for AD
are reported to have a sensitivity of 95% and a specificity of 79% (Lopez et al.,
1999), whereas the CDLB criteria for DLB have a sensitivity of 57–83% and a
specificity of 90–95% (Luis et al., 1999), and the NINDS-AIREN and ADDTC
criteria for VaD and IVaD dementias have, respectively, sensitivities of 55%
and 70%, as well as specificities of 84% and 78% (Gold et al., 2002). Thus
the criteria for AD and other dementias can be used appropriately in clinical
neuropsychological studies.
Finally, the cognitive tests that were used in this study do not provide an
exhaustive neuropsychological profile of the subjects, and hence it is possible
that some specific cognitive alterations have not been documented. The MMSE
and DRS are, nonetheless, valid measures that have high sensitivity to detect
deterioration of cognitive functions in AD and other dementias (Salmon et al.,
1990), and they are easy and speedy to administer. They are thus suitable for
clinical purposes in this population. In addition, the Initiation/Perseveration,
Memory and Conceptualization subtests of the Mattis DRS share common
features with tests proved to be useful to detect dementia in the preclinical
phases of AD (Jacobs et al., 1995).
To conclude, the identification of differential cognitive impairment among
depressed elderly people who will develop different kinds of dementia may
eventually improve the prognosis of neurodegenerative dementias. In the future,
the possibility of administering cognitive and pharmacological treatments as
soon as the cognitive markers are identified may certainly contribute to the
maintenance of the cognitive and functional capacities of elderly depressed
individuals. From a neuropsychological perspective, future research on cognitive
markers for depressed individuals and other elderly populations at high risk of
developing dementia is supported by the current findings.
Cognitive impairment in geriatric depression 299
Conflict of interest
None.
Description of authors’ roles
L´
eonie Jean was the principal author, defined the research question, performed
statistical analyses, and wrote the abstract and the introduction and discussion
sections. Martine Simard collected the data, formulated the research question,
performed statistical analyses, wrote the method and results sections, and was the
senior responsible author. Robert van Reekum created the follow-up database
used in this paper and collected the follow-up data. He was the principal
investigator of the follow-up study and provided comments on the draft paper.
Diana E. Clarke was the co-creator of the follow-up database and manager of
the original database, both used in this paper. She collected the follow-up data,
and commented on the draft paper.
Acknowledgments
Part of these results were presented at the 32nd Annual Meeting of the
International Neuropsychological Society, which took place in Baltimore,
U.S.A., February 4–7, 2004.
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