Engaging in Cognitive Activities, Aging, and Mild Cognitive Impairment: A Population-Based Study

Abstract

The authors investigated whether engaging in cognitive activities is associated with aging and mild cognitive impairment (MCI) in a cross-sectional study derived from an ongoing population-based study of normal cognitive aging and MCI in Olmsted County, MN. A random sample of 1,321 study participants ages 70 to 89 (N=1,124 cognitively normal persons, and N=197 subjects with MCI) were interviewed about the frequency of cognitive activities carried out in late life (within 1 year of the date of interview). Computer activities; craft activities, such as knitting, quilting, etc.; playing games; and reading books were associated with decreased odds of having MCI. Social activities, such as traveling, were marginally significant. Even though the point-estimates for reading magazines, playing music, artistic activities, and group activities were associated with reduced odds of having MCI, none of these reached statistical significance. The equally high prevalence of reading newspapers in both groups yielded no significant between-group difference.

Full text

Engaging in Cognitive Activities, Aging and Mild Cognitive
Impairment: A Population-Based Study
Yonas E. Geda, MD, MSc, Hillary M. Topazian, Lewis A. Roberts, Rosebud O. Roberts, MB
ChB, MS, David S. Knopman, MD, V. Shane Pankratz, PhD, Teresa J.H. Christianson, BSc,
Bradley F. Boeve, MD, Eric G. Tangalos, MD, Robert J. Ivnik, PhD, and Ronald C. Petersen,
MD, PhD
Department of Health Sciences Research, Divisions of Epidemiology (Drs. Geda, Petersen, and
Roberts), Biomedical Statistics and Informatics (Ms. Christianson and Dr. Pankratz). Departments
of Psychiatry and Psychology (Drs. Geda, Ivnik), Neurology (Drs. Boeve, Knopman, and
Petersen), and Primary Care Internal Medicine (Dr. Tangalos), College of Medicine, Mayo Clinic,
Rochester MN, USA. Wheaton University (Topazian), Chicago IL, Rice University, Houston, TX
(LA Roberts) USA
Abstract
We investigated whether engaging in cognitive activities is associated with mild cognitive
impairment (MCI) in a cross-sectional study derived from an ongoing population-based study of
normal cognitive aging and MCI in Olmsted County, Minnesota. A random sample of 1321 non-
demented study participants ages 70 to 89 (n = 1124 cognitively normal persons and n = 197
subjects with MCI) was interviewed about the frequency of cognitive activities carried out in late
life (within one year of the date of interview). Computer activities [OR (95% CI) = 0.50 (0.36,
0.71); p < .0001)], craft activities such as knitting, quilting, etc. [0.66 (0.47, 0.93); p = 0.019)],
playing games [0.65 (0.47, 0.90); p = 0.010)], and reading books [0.67 (0.49, 0.94); p = 0.019)]
were associated with decreased odds of having MCI. Social activities such as traveling were
marginally significant [0.71 (0.51, 1.00); p = 0.050)]. Even though the point estimates for reading
magazines, playing music, artistic activities, and group activities were associated with reduced
odds of having MCI, none reached statistical significance. We could not expect to observe any
difference between the two groups on the variable of reading newspapers since almost identical
proportions of the two groups (97.4% of normals and 97.5% of the MCI group) were engaged in
reading newspapers on a regular basis.
Keywords
cognitive activities; aging; mild cognitive impairment
Mild cognitive impairment (MCI) is the intermediate stage between the cognitive changes of
normal aging and dementia 1. The reader is referred elsewhere for a detailed discussion of
Corresponding Author: Yonas E. Geda, MD, MSc. Associate Professor of Neurology and Psychiatry. College of Medicine, Mayo
Clinic. 200 First Street SW, Rochester, MN 55905, USA. geda.yonas@mayo.edu.
Author Contributions: Dr. Geda had full access to all the data in the study and takes responsibility for the integrity of the data and
the accuracy of the data analysis. Study concept and design: Geda, Roberts, Knopman, Petersen. Acquisition of data: Geda, Knopman,
Boeve, Tangalos, Petersen. Analysis and interpretation of data: Geda, Christianson, and Pankratz. Drafting of the manuscript: Geda.
Critical revision of the manuscript for important intellectual content: Geda, Roberts, Knopman, Christianson, Pankratz, Topazian,
Boeve, Tangalos, and Petersen. Statistical analysis: Christianson, Pankratz. Obtained funding: Geda, Petersen. Administrative,
technical, and material support: Geda, Petersen. Study supervision: Roberts, Petersen.
Financial Disclosure: None reported.
NIH Public Access
Author Manuscript
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Published in final edited form as:
J Neuropsychiatry Clin Neurosci
. 2011 ; 23(2): 149–154. doi:10.1176/appi.neuropsych.23.2.149.
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MCI 2, 3. Subjects with MCI constitute a high risk group because they develop dementia at a
rate of 10% to 15% per year compared with 1% to 2% per year in the general population 4.
In view of this, it is critical to identify potential protective factors against MCI. Previous
studies have reported an association between cognitive activities and reduced risk of
incident dementia 5-7. However, little is known about the association between cognitive
activities and the odds of having MCI. A convenience sample of a prospective cohort study
involving community-dwelling elderly participants reported that baseline cognitive activities
were associated with decreased risk of amnestic MCI8. There is a need to examine this
question in a population-based setting using a larger sample.
We examined whether engaging in cognitive activities is associated with MCI in a cross-
sectional study derived from an ongoing population-based study of normal cognitive aging
and MCI in Olmsted County, Minnesota. Throughout this manuscript, one can
interchangeably think of the phrase “cognitive activity” to be equivalent to “mental activity”
or “intellectual activity”.
METHODS
SETTING
The detail of the design and conduct of the Mayo Clinic Study of Aging was reported
elsewhere 9. Briefly, it is an on-going population-based study of normal aging and MCI in
Olmsted County, Minnesota. Elderly persons ages 70 to 89 on the prevalence date of
October 1, 2004, were recruited by using a stratified random sampling from the target
population of nearly 10,000 elderly individuals in Olmsted County, Minnesota. The
sampling involved equal allocation of men and women in two age strata: 70 to 79 and 80 to
89 years old. During the first follow-up phase of the study, which took place between 2006
through 2008, we introduced a structured interview format to collect data on cognitive
activities. 1,321 non-demented study participants completed the interview. At the time of the
interview, neither the study participant nor the research personnel knew the case-control
status of a participant. The classification of a study participant as having MCI or not was a
downstream event to the collection of data on cognitive activities. The details of the
classification process of MCI are discussed elsewhere in this paper. The study was approved
by the institutional review boards of Mayo Clinic and the Olmsted Medical Center.
STUDY DESIGN
A population-based cross-sectional study involving 1,321 non-demented study participants
(n = 197 subjects with MCI and n = 1,124 cognitively normal persons).
MEASUREMENT OF MCI
The association of interest in this study is between cognitive activities and the odds of
having MCI. Each participant in the Mayo Clinic Study of Aging underwent the following
three face-to-face evaluations: (1) neurological evaluation by a physician; (2) risk factor
assessment by a nurse or study coordinator; and (3) neuropsychological testing that was
interpreted by a neuropsychologist. The interview by the nurse or study coordinator included
administration of the Clinical Dementia Rating Scale 10 to the participant and to an
informant. The neurological evaluation was performed by a physician and included
administration of the Short Test of Mental Status 11, medical history review, and a complete
neurological examination.
Neuropsychological testing was performed to assess four cognitive domains: (1) memory
(Logical Memory-II [delayed recall] and Visual Reproduction-II [delayed recall] from
Wechsler Memory Scale-Revised, and delayed recall from the Auditory Verbal Learning
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Test) 12-15; (2) executive function (Trail Making Test B 16, and Digit Symbol Substitution
from Wechsler Adult Intelligent Scale-Revised); (3) language (Boston Naming Test 17, and
category fluency) 18; and (4) visuospatial skills (Picture Completion and Block Design from
WAIS-R).
We considered as cases all the participants who met the revised Mayo Clinic criteria for
MCI: (1) cognitive concern expressed by a physician, informant, participant, or nurse; (2)
cognitive impairment in one or more domains (executive function, memory, language, or
visuospatial); (3) normal functional activities; and (4) not demented 2, 3. Subjects with MCI
could have a Clinical Dementia Rating Scale score of 0 or 0.5; however, the final diagnosis
of MCI was not based exclusively on the clinical dementia rating, but rather on all available
data. The diagnosis of normal cognition, MCI, dementia, or Alzheimer’s disease was made
by an expert consensus panel of physicians, psychologists, and nurses based on published
criteria 12, 13, 19-21. The panel meets once per week and reviews three independent sources of
data, i.e., the clinical data collected by behavioral neurologists and physicians of other
specialties with expertise in dementia and MCI, neuropsychological data collected by
psychometrists who are supervised by neuropsychologists, and nursing data gathered by
research nurses 9.
MEASUREMENT OF COGNITIVE ACTIVITIES
We defined the exposure of interest to be reading, craft activities, computer activities,
playing games, playing music, group activities (e.g., book club), social activities (e.g., going
out to movies and theaters), artistic activities, and watching television. We modified
previously validated instruments to measure these activities 6, 22, 23. A research nurse or
psychometrist interviewed each participant by using a structured survey with ordinal
responses (e.g., reading books at a frequency of once per week, twice per week, etc.) The
participants were asked to provide information about these activities within a year of the
date of interview (late life cognitive activity). The measurement of cognitive activities was
conducted along with neurological evaluation, neuropsychological assessment and risk
factor ascertainments. Once these data were collected, then a consensus panel of experts
classified the study participant to be cognitively normal or to have MCI.
MEASUREMENT OF COVARIATES
In addition to traditional confounders (age, sex, and education), we also defined medical
comorbidity and depression to be covariates for the purpose of this study. We measured
medical comorbidity by using the Charlson index, which is a widely used weighted index
that takes into account the number and severity of diseases. Thus for each unit increase in
Charlson index, there is a stepwise increase in the cumulative mortality attributable to the
comorbid medical disease 24. We measured depression by using the Beck Depression
Inventory-II 25. Additionally, we adjusted for physical exercise by assigning a numeric score
to frequency of physical exercise and adding the scores across the light, moderate, and
vigorous strata (equal weighting to all strata). The details of the physical exercise
measurement were reported elsewhere 26.
STATISTICAL ANALYSIS
Multi-variable logistic regression analyses were conducted to examine the strength of
association of cognitive activities with the odds of having MCI by computing odds ratios
and corresponding 95% confidence intervals. The primary analysis was conducted by
adjusting for traditional confounders (age [continuous variable], sex, and education
[continuous variable]). We also conducted secondary analysis by adjusting for medical
comorbidity (weighted Charlson index as a continuous variable), depressive symptoms
(BDI-II score <13 versus ≥13), and physical exercise (continuous variable).26.
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The frequency of each activity was dichotomized as none (once per month or less) versus
any other frequency. We considered watching television to be hypothetically less beneficial,
therefore watching TV was “reverse” scored, i.e., watching more television (>6 hours/day)
versus watching less (≤ 6 hours/day).
Analyses were conducted for cognitive activity carried out in late life (within the past one
year). Statistical testing was done at the conventional 2-tailed alpha level of 0.05. All
analyses were performed by using SAS (Cary, NC).
RESULTS
Table 1 summarizes the demographic data. There were 1,321 non-demented study
participants (n = 1,124 cognitively normal persons, n = 197 subjects with MCI). Among the
cognitively normal group (normals), there were an equal number of males and females,
whereas among the MCI group there were more males than females. On average, the MCI
group was older than the normal group. The two groups also significantly differed in
education, medical comorbidity, and depressive symptoms. Therefore, in the primary
analysis the comparison of engaging in cognitive activities between the two groups was
made after adjusting for age (continuous variable), sex, and education (continuous variable).
In a secondary analysis, we also adjusted for depressive symptoms, medical comorbidity and
physical exercise.
Table 2 displays the data comparing the two groups as measured by OR (95% CI). Reading
books [0.67 (0.49, 0.94)], playing games [0.65 (0.47, 0.90)], craft activities (quilting,
pottery, etc.) [0.66 (0.47, 0.93)], and computer activities [0.50 (0.36, 0.71)] were
significantly associated with decreased odds of having MCI. The point estimate for social
activity (e.g., going out with friends) was also associated with decreased odds of having
MCI, but this association was marginally significant [0.71 (0.51, 1.00)].
The point estimates for reading magazines [0.81 (0.49, 1.32)], playing music [0.79 (0.50,
1.25)], artistic activities [0.81 (0.49, 1.32)], and group activities [0.88 (0.64, 1.22)] were
associated with reduced odds of MCI; however, none reached statistical significance. The
only exception to the overall trend was the cognitive activity of reading newspapers. The OR
for reading newspapers [1.13 (0.43, 2.99)] was suggestive of increased odds of having MCI;
however, close examination of the data indicates that almost identical proportions of the two
groups engaged in regular newspaper reading (97.4% of the cognitively normal group vs
97.5% of the MCI group were reading newspapers on a regular basis).
We considered watching television to be a hypothetically less beneficial activity, therefore
watching TV was “reverse” scored, i.e., watching more television (>6 hours/day) versus
watching less (≤ 6 hours per day). We observed that watching less TV was associated with
decreased odds of MCI [OR (95% CI) = 0.48 (0.27, 0.86); p= 0.013].
In the secondary analysis, additional adjustment for depressive symptoms, medical
comorbidity and physical exercise did not affect the significance level observed in the
primary analysis (data not shown).
DISCUSSION
In this population-based cross-sectional study we observed that cognitive activities such as
computer use, playing games, reading books, craft activities (quilting, knitting, etc.) and
watching less TV were associated with 30% to 50% reduced odds of having MCI. Social
activities such as traveling were marginally significant. Even though the point estimates for
reading magazines, playing music, artistic activities, and group activities were associated
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with reduced odds of having MCI, none reached statistical significance. Almost identical
proportions of the two groups were engaged in reading newspapers on a regular basis,
therefore we could not observe a significant difference between the two groups.
Several studies have reported the association of cognitive/intellectual or ‘mental’ activities
with decreased risk of incident dementia5-7. However, little is known about the association
of cognitive activities with MCI. The Bronx Aging Study prospectively followed a
convenience sample of 437 community-dwelling cognitively normal elderly persons ages 75
and older to the outcome of incident amnestic MCI 8. During the median follow-up duration
of 5.7 years, there were 58 subjects who developed incident amnestic MCI. The
investigators noted that a unit increase in cognitive activity was associated with a 5%
decreased risk of incident amnestic MCI. Even though the Bronx study was a convenience
sample, the prospective study design would enable one to make some degree of etiologic
inferences. The investigators retrofitted the MCI criteria; hence this might have potentially
led to misclassification errors. Although our study is population-based, the cross-sectional
design does not allow one to make etiologic inferences. Therefore, the observations made in
our current study need to be tested on a larger sample in a prospective cohort design.
The findings of our study should be interpreted within the context of the following
limitations. The first limitation pertains to study design. Since this was a cross-sectional
study, we cannot determine the direction of causality between the hypothesized exposure of
interest (i.e., cognitive activity) and the hypothesized outcome of interest (i.e., MCI).
Second, like any survey based study, recall bias is a potential limitation. This is even more
relevant to participants with MCI; however, at our center the data on cognitive activities are
collected prior to determination of whether a person has MCI or not. Therefore, neither the
participant nor the research personnel knew the case control status of the participant at the
time of administration of the cognitive activities questionnaire. This likely minimized bias,
but could not eliminate it. Additionally, in the past we had reported that the test-retest
correlations were similar among subjects with normal cognition and MCI 26.
Our study did not address mechanism of action. However, the possible beneficial impact of
cognitive activities as discussed in the literature is worth mentioning. Engaging in cognitive
activities may be a marker for an overall healthy lifestyle, e.g., a person who likes to read
books on a regular basis may also engage in an overall healthy lifestyle that includes
exercise, diet, and stress management. Another possible explanation is related to the brain/
cognitive reserve hypothesis 27, 28. Engaging in cognitive activity is more likely to reinforce
and perhaps stimulate the formation of various neuronal networks in the brain 28 that can
buffer against dementia and Alzheimer’s disease 29. This argument is supported by both
basic science and clinical research. For instance, animals with enriched environments are
protected against cognitive impairment 28, 30. Additionally in clinical settings it is also
observed that clinical manifestations may not correlate with the neuropathological burden on
postmortem examination 6, 31-33, implying that the cognitive reserve may serve as a buffer
against the Alzheimer’s disease neuropathological burden. Since MCI is considered to be a
prodromal state to Alzheimer’s disease, one can invoke the cognitive reserve theory to
explain the inverse association between cognitive activities and the odds of having MCI.
Yet, another potential mechanism pertains to the classic stress model proposed by Sapolsky
and colleagues 34. According to this model, the hippocampus, which is the epicenter of the
memory network 35, has a number of glucocorticoid receptors. These receptors are down
regulated in excessively stressful situations. Thus, cognitive activities may serve as stress
modifying agents, leading to decreased “neurotoxic” insult to the hippocampus and related
structures pertinent to cognition and emotion.
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In summary, our findings contribute to the growing body of literature that indicates that
cognitive activities are associated with decreased odds of having MCI. A future prospective
population-based cohort study needs to confirm whether cognitive activity is associated with
a decreased risk of incident MCI. We are following a large cohort of cognitively normal
persons to the outcome of incident MCI; thus we will be able to test the observation made
from the current cross-sectional study. The population based setting will improve
generalizability, and the prospective cohort will strengthen etiologic inferences.
Acknowledgments
The authors would like to express their appreciation to Stephanie K. Cheung, a summer research student from
Columbia University for their help in the final editing of the manuscript.
Funding/Support: This study was supported by grants from the National Institutes of Health (K01 MH68351;
AG06786, Mayo CTSA (RR024150 [Career Transition Award]), the RWJ Foundation (Harold Amos Scholar), and
from the Robert H. and Clarice Smith and Abigail Van Buren Alzheimer’s Disease Research Program.
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Table 1
Demographic Characteristics of Study Participants
Variable Normal (N = 1,124) MCI (N = 197) P-value
Men, n (%) 564 (50.2) 116 (58.9) 0.024
Age, yearsa80 (72-93) 83 (72-93) <0.001
Education, yearsa13 (6-20) 12 (6-20) 0.001
>12 years, n (%) 651 (57.9) 91 (46.2)
BDI-II Depression ( ≥13)b62 (5.5) 29 (14.8) <0.001
Charlson Indexc2 (1-5) 3 (2-6) <0.001
aMedian (range).
b1 patient missing BDI (1 MCI).
cMedian (interquartile range).
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Table 2
Cognitive Activities Carried Out Within 1 year of the Date of Interview
Activity Normal (N=1124) N (%) MCI (N=197) N (%) OR (95% CI)aP-value
Reading newspapers 1095 (97.4) 192 (97.5) 1.13 (0.43, 2.99) 0.81
Reading magazines 1033 (91.9) 174 (88.3) 0.81 (0.49, 1.32) 0.39
Reading books 776 (69.1) 111 (56.3) 0.67 (0.49, 0.94) 0.019
Play games 795 (70.7) 118 (59.9) 0.65 (0.47, 0.90) 0.010
Play music 203 (18.1) 25 (12.7) 0.79 (0.50, 1.25) 0.31
Artistic activities 159 (14.1) 21 (10.7) 0.81 (0.49, 1.32) 0.39
Craft activities 455 (40.5) 57 (28.9) 0.66 (0.47, 0.93) 0.019
Group activities 456 (40.6) 71 (36.0) 0.88 (0.64, 1.22) 0.45
Social activities 871 (77.5) 134 (68.0) 0.71 (0.51, 1.00) 0.050
Computer activities 549 (48.8) 58 (29.4) 0.50 (0.36, 0.71) <0.001
aOR, odds ratios and CI, confidence intervals were computed by comparing frequencies of activities carried once a month or less (reference) versus
any other frequency of activity. Findings are Adjusted for age, sex, and education. Secondary analysis also adjusted for, depression, medical
comorbidity (Charlson index) and physical exercise. We did not observe any significant difference from the primary analysis (data not shown).
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