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A Prospective Study of Physical Activity and Cognitive Decline in Elderly Women
Women Who Walk
Kristine Yaffe, MD;
Deborah Barnes, MPH;
Michael Nevitt, PhD;
Li-Yung Lui, MA, MS;
Kenneth Covinsky, MD
Arch Intern Med. 2001;161:1703-1708.
ABSTRACT
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Background Several studies have suggested that physical activity is positively
associated with cognitive function in elderly persons. Evidence about this
association has been limited by the cross-sectional design of most studies
and by the frequent lack of adjustment for potential confounding variables.
We determined whether physical activity is associated with cognitive decline
in a prospective study of older women.
Methods We studied 5925 predominantly white community-dwelling women (aged  65
years) who were recruited at 4 clinical centers and were without baseline
cognitive impairment or physical limitations. We measured cognitive performance
using a modified Mini-Mental State Examination at baseline and 6 to 8 years
later. Physical activity was measured by self-reported blocks (1 block 
160 m) walked per week and by total kilocalories (energy) expended per week
in recreation, blocks walked, and stairs climbed. Cognitive decline was defined
as a 3-point decline or greater on repeated modified Mini-Mental State Examination.
Results Women with a greater physical activity level at baseline were less likely
to experience cognitive decline during the 6 to 8 years of follow-up: cognitive
decline occurred in 17%, 18%, 22%, and 24% of those in the highest, third,
second, and lowest quartile of blocks walked per week (P<.001 for trend). Almost identical results were obtained by quartile
of total kilocalories expended per week. After adjustment for age, educational
level, comorbid conditions, smoking status, estrogen use, and functional limitation,
women in the highest quartile remained less likely than women in the lowest
quartile to develop cognitive decline (for blocks walked: odds ratio, 0.66
[95% confidence interval, 0.54-0.82]; for total kilocalories: odds ratio,
0.74 [95% confidence interval, 0.60-0.90]).
Conclusions Women with higher levels of baseline physical activity were less likely
to develop cognitive decline. This association was not explained by differences
in baseline function or health status. This finding supports the hypothesis
that physical activity prevents cognitive decline in older community-dwelling
women.
INTRODUCTION
AT LEAST 10% of persons older than 65 years and 50% of those older than
85 years have some form of cognitive impairment, ranging from mild deficits
to dementia.1 The identification of risk factors
associated with cognitive decline, especially ones that may lead to prevention
or intervention strategies, is critical. Physical activity has been identified
as a possible risk factor that might be amenable to such interventions. There
are several possible mechanisms by which physical activity could affect cognitive
function, including increasing cerebral blood flow,2
reducing the risk of cardiovascular and cerebrovascular disease,3
and stimulating neuronal growth and survival.4
While some studies support the hypothesis that increased levels of physical
activity are associated with preserved cognitive function, several methodological
considerations limit the ability to draw conclusions from these studies. For
example, several cross-sectional studies5-9
have demonstrated that physically active elderly persons perform better on
cognitive testing than inactive elderly persons. However, cause-effect associations
are difficult to determine in these cross-sectional studies since it is not
clear whether cognitive impairment leads to lower levels of physical activity
or vice versa. Only 2 prospective studies have been conducted; one10 found an association between energy expended from
strenuous, but not moderate, activities and preservation of cognitive function
over 2 to 3 years in 1011 community-dwelling elderly persons. The subjects
in that study were part of a well-functioning group of elderly persons and
the measurement of physical activity did not include recreational or walking
activities, only daily activities around the house. The other prospective
study11 did not find an association between
physical activity and cognitive decline in 327 Australian older men and women
followed up for 3 years. However, this study may have had limited power due
to a small sample size and a short follow-up.
Therefore, we examined the association between baseline physical activity
(daily activities and recreational activities) and cognitive decline during
8 years of follow-up in elderly community-dwelling women participating in
an ongoing prospective study. We excluded women with baseline cognitive impairment
or physical limitations, and we adjusted for several potential confounders
of the association between physical activity and cognitive function, including
baseline function and health status.
SUBJECTS AND METHODS
SUBJECTS
All women were enrolled in the Study of Osteoporotic Fractures,12 a prospective study of risk factors for fractures
among 9704 predominantly white community-dwelling women 65 years or older.
Participants were recruited from population-based listings in 4 areas of the
United States: Baltimore, Md; Minneapolis, Minn; the Monongahela Valley near
Pittsburgh, Pa; and Portland, Ore. Black women were excluded because of their
low incidence of fracture, as were women who were unable to walk without assistance
or who had bilateral hip replacements. All participants were interviewed and
examined during the baseline visit (1986-1988). Participants then underwent
biennial clinic visits and completed annual questionnaires.
Because we were interested in whether physical activity was associated
with the risk of developing cognitive decline prospectively, we excluded women
with baseline cognitive impairment (modified Mini-Mental State Examination
[mMMSE] score <23 of possible 26 [n = 950]), women with missing baseline
cognitive scores (n = 53), women with baseline physical limitations (subjects
who said that they were unable to stand up unaided from a chair or to walk
up stairs because of an injury or health condition [n = 939]), women with
missing information on physical limitations (n = 10), and women who did not
complete baseline physical activity assessments (n = 51). Of the remaining
7701 women, 596 (8%) died, 238 (3%) were unavailable for follow-up, and 942
(12%) did not have follow-up cognitive measurements (either 6- or 8-year measurements).
The remaining 5925 subjects who completed cognitive tests at baseline and
follow-up form the analytic cohort for this study. Women who did not have
cognitive follow-up measurements had lower baseline scores on cognitive testing
and were less physically active compared with the 5925 women in the final
analytical cohort (P<.001 for all comparisons).
All subjects provided written informed consent, and the study was approved
by the committees on human research at each site.
MEASUREMENT OF PHYSICAL ACTIVITY
We measured physical activity at baseline by asking how many city blocks
(1 block 160 m) (or the equivalent) the women walked each day for exercise
or as part of their normal routine and how many flights of stairs they climbed
up each day. We also measured physical activity using a modified Paffenbarger
Scale,13 in which trained interviewers asked
the subjects to report the frequency and duration of their participation per
week during the past year in 33 different physical activities. Specifically,
the women were asked, "Did you participate in any physical activities, recreation,
or sport in the past week?" If the answer was yes, the subjects were asked
how often (weeks per year and times per week) and for how long they participated
in the activity. The activities were classified according to low (walking
or gardening), medium (dancing or tennis), or high (jogging or skiing) intensity
and assigned energy expenditures of 5.0, 7.5, or 10.0 kcal/min, respectively,
according to previously reported methods.14
Total physical activity, expressed in kilocalories (energy) expended per week,
was calculated by adding kilocalories expended in the 33 recreational activities,
blocks walked (8 kcal per block), and stairs climbed (4 kcal per flight).
For our analyses, our primary measures of physical activity were blocks walked
per week and total kilocalories expended per week.
MEASUREMENT OF COGNITIVE FUNCTION
A trained examiner administered the cognitive testing during the baseline
clinic visit and at the follow-up visits 6 and 8 years later. The mMMSE, which
does not include some questions assessing orientation, was administered.15 This is a brief global cognitive function test with
concentration, language, and memory components designed to screen for cognitive
impairment. The mMMSE has a potential range of 0 to 26, with higher numbers
indicating better performance (subjects with baseline scores <23 were excluded
from the analytic cohort). We defined cognitive decline as a decrease of 3
or more points on the mMMSE from baseline to the 6- or 8-year follow-up (whichever
was lower). This definition has been previously used for the full MMSE to
identify the onset of dementia in a group of community-dwelling elderly persons.16
OTHER VARIABLES
At the initial study visit, we ascertained age, highest level of education,
weekly alcohol use, current smoking, and history of comorbid health conditions
(eg, stroke, myocardial infarction, Parkinson disease, diabetes, and hypertension).
We asked subjects to rate their overall health compared with other women as
excellent, good, fair, poor, or very poor. Functional status was assessed
by asking the subjects the amount of difficulty they had with each of 6 activities
(preparing meals, shopping, lifting heavy items, dressing, bathing, and transferring)
based on a modified version of the Stanford Health Assessment Questionnaire.17 We defined functional impairment as being present
if the respondent reported much difficulty with 1 or more of these activities.
The 15-item Geriatric Depression Scale was administered shortly after the
study began.18 Scores range from 0 to 15, with
higher scores indicating more symptoms of depression. During each clinic examination,
we measured weight and height; body mass index was defined as weight in kilograms
divided by the square of height in meters. Participants were asked about current
use of oral estrogen therapy, and reports of current medications were checked
by examining labels of drugs brought to the clinic. Baseline walking (gait)
speed was determined from the average of 2 trials of the time (seconds) needed
to walk 12 m.
STATISTICAL ANALYSIS
Because the distributions of blocks walked per week and total kilocalories
expended per week were not normally distributed (skewed to the left), we divided
subjects into approximate quartile of physical activity. Baseline subject
characteristics were compared by analysis of variance for continuous variables
and by the  2 test for dichotomous variables across quartiles.
We used logistic regression analyses to examine the odds of cognitive decline
(a decrease of 3 points on the mMMSE) as a function of physical activity
quartile using the lowest quartile as a reference. We then adjusted the models
for covariates that either were associated (P<.05)
with physical activity quartile and with cognitive decline (age, educational
level, depression, a history of hypertension or diabetes, estrogen use, and
smoking) or could affect the ability to be physically active (baseline functional
limitation, self-reported health status, and medical comordities such as a
history of stroke or myocardial infarction). We also analyzed the odds of
cognitive decline as a function of physical activity in subgroups of women
(aged  70 or >70 years, educational level <12 or 12 years, and presence
or absence of comorbid health conditions). Using the cognitive score as a
continuous outcome, we determined if change in score (and percentage change
of the initial score) on the mMMSE was associated with quartile of exercise
(blocks walked or total kilocalories) using linear regression models. To determine
if baseline physical performance could explain an association between exercise
and cognitive decline, we also examined whether baseline walking speed was
associated with cognitive decline using logistic regression. All significance
levels reported are 2-sided, and all analyses were performed using SAS statistical
software (SAS Institute Inc, Cary, NC).
RESULTS
Women reported a wide range of walking activity, with a median of 49
blocks walked per week. Ten percent of the women never walked for exercise
or for daily activities, while 10% walked 200 or more blocks per week. The
median numbers (ranges) of blocks walked per week in the lowest, second, third,
and highest quartile were 7 (0-22), 28 (23-49), 77 (50-112), and 175 (113-672),
respectively. Similarly, the participants reported a wide range of total physical
activity, with a median total expenditure of 1323 kcal/wk. Nearly 5% of the
women reported that they were completely sedentary, and 5% expended more than
5000 kcal/wk. The median numbers (ranges) expended in the lowest, second,
third, and highest quartile were 336 (0-615), 936 (616-1323), 1773 (1324-2414),
and 3469 (2415-17 531) kcal/wk, respectively. Women in the highest physical
activity quartiles (measured by total kilocalories expended) were younger,
were more educated, were more likely to be taking estrogen and to drink alcohol,
were less likely to smoke, had fewer comorbid medical conditions, had a lower
body mass index, had lower depression scores, and had less functional limitation
than women in the lower quartiles (P.05 for all)
(Table 1). A similar pattern of
differences was seen for women across quartile of blocks walked. Mean ±
SD mMMSE scores at baseline were slightly, but probably not clinically significantly,
lower in the lowest physical activity quartile compared with the higher quartiles
(25.1 ± 1.0 for the lowest quartile vs the second and third quartiles
and 25.2 ± 0.9 for the highest quartile P
= .001).
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Table 1. Baseline Characteristics of 5921 Women by Quartile of Total
Kilocalories (Energy) Expended*
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During the mean of 7.5 years of follow-up, women declined a mean ±
SD of 1.0 ± 2.1 points on the mMMSE, and 1178 (20%) of the participants
developed cognitive decline (3 points of decline on repeated mMMSEs).
Twenty-four percent of the women in the lowest quartile of blocks walked per
week developed cognitive decline compared with 17% of the women in the highest
quartile (P<.001) (Table 2). Similarly, 24% of the women in the lowest quartile of
total kilocalories expended per week developed cognitive decline vs 17% of
the women in the highest quartile (P<.001). Compared
with the lowest quartile, the odds of developing cognitive decline were 37%
lower (odds ratio [OR], 0.63; 95% confidence interval [CI], 0.53-0.76) in
the highest quartile of blocks walked and 35% lower (OR, 0.65; 95% CI, 0.54-0.78)
in the highest quartile of total kilocalories expended. There was a significant
trend for more exercise to be associated with a greater reduction of odds
of cognitive decline (P<.001 for trend for quartiles
of blocks walked and total kilocalories expended per week). Moreover, for
every 10 blocks walked per day (approximately 1.6 km [1 mile]), women had
a 13% (OR, 0.87; 95% CI, 0.82-0.92) lower odds of cognitive decline. For every
SD (1700 kcal) of total kilocalories expended per week for physical activity,
there was a 14% (OR, 0.86; 95% CI, 0.80-0.92) lower odds of cognitive decline.
Compared with women without cognitive decline, women who developed cognitive
decline on average were older (mean ± SD age, 72.2 ± 5.2 vs
70.4 ± 4.5 years; P<.001), were less educated
(mean ± SD years of education, 12.6 ± 2.8 vs 13.0 ± 2.6; P<.001), had more symptoms of depression (mean ±
SD, 1.6 ± 2.1 vs 1.4 ± 1.9 symptoms; P<.001),
were more likely to have a history of hypertension (38% vs 35%; P = .03), were less likely to be taking oral estrogen replacement therapy
(13% vs 16%; P = .01), and were less likely to smoke
(7% vs 9%; P = .009).
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Table 2. Frequency of Cognitive Decline According to Physical Activity
Quartile in 5925 Older Women*
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After adjusting for baseline age, educational level, health status,
functional limitation, depression score, stroke, diabetes, hypertension, myocardial
infarction, smoking, and estrogen use, women with higher levels of physical
activity remained at lower risk for cognitive decline (Table 2). To determine if baseline physical performance could have
explained some of the association between exercise and cognitive decline,
we examined whether baseline walking speed was associated with cognitive decline.
In the age- and multivariate-adjusted models, quartile of baseline walking
speed was not associated with risk of cognitive decline (for lowest quartile
of walking speed: age-adjusted OR, 1.04 [95% CI, 0.87-1.25]; and multivariate-adjusted
OR, 1.06 [95% CI, 0.86-1.30]).
To determine whether the association between physical activity and cognitive
decline was consistent across subgroups of women with different propensities
for exercise, we stratified the women into groups according to age (70
or >70 years), the presence or absence of comorbid medical conditions, and
educational level (<12 or 12 years) (Table 3). Across all subgroups, women in the higher physical activity
quartiles had lower odds of cognitive decline.
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Table 3. Odds of Cognitive Decline Associated With Physical Activity
Quartile in Subgroups of Women
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We also examined the association between physical activity quartiles
and mMMSE score change (as a continuous variable). Quartile of blocks walked
or total kilocalories expended was associated with 6- to 8-year change in
mMMSE score (for quartile of blocks walked: regression coefficient, -0.14
[P<.001]; and for quartile of total kilocalories:
regression coefficient, -0.08 [P<.001]).
We calculated the percentage change in age-adjusted mMMSE score (as a function
of baseline score) and found that women in the higher physical activity quartiles
(measured by blocks walked) had less percentage decline during the 6 to 8
years compared with women in the lower quartiles (Figure 1).
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Percentage decline in age-adjusted modified Mini-Mental State Examination
(mMMSE) score during the 6- to 8-year follow-up as a function of physical
activity (blocks [1 block 160 m] walked). The median numbers (ranges)
of blocks walked per week in the lowest, second, third, and highest quartiles
were 7 (0-22), 28 (23-49), 77 (50-112), and 175 (113-672), respectively. The
difference between women in the higher quartiles and those in the lower quartiles
was significant (P<.001).
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COMMENT
In this prospective study of 5925 community-dwelling women, subjects
with greater baseline physical activity, whether measured as blocks walked
per week or as total kilocalories expended per week, were less likely to develop
cognitive decline during the 6- to 8-year follow-up. This association remained
after adjustment for covariates, including baseline functional and health
status, and did not seem to be explained by differences in baseline physical
performance measures. The strengths of our study are its large sample size
and prospective design and the fact that we excluded subjects who had cognitive
or physical limitations at baseline.
Our results are supported by several cross-sectional studies5-9
in which elderly persons who were physically active performed better on cognitive
testing compared with those who were inactive. One prospective study10 has reported that strenuous, but not moderate, daily
activities were associated with less cognitive decline in a healthy older
cohort. We found that moderate, as well as strenuous, physical activity was
associated with decreased risk. In our study, examples of moderate physical
activity included playing 18 holes of golf once a week, playing tennis twice
a week, or walking 1.6 km/d. Moderate levels of physical activity in elderly
cohorts have also been shown to reduce mortality from coronary heart disease19 and overall mortality,20
to reduce the risk of osteoporotic fractures,21
and to improve bone mineral density.22
Several trials,23-25
most lasting several months, have failed to demonstrate a benefit of exercise
interventions on cognitive function among older adults, while other trials6, 26-28 have
found improved cognitive performance with physical activity. It is possible
that physical activity may prevent cognitive decline but not improve cognitive
performance during a short period in otherwise high-functioning elderly persons.
This is plausible if physical activity–induced effects are associated
with long-term protective benefits, such as a reduction in cardiovascular
or cerebrovascular risk factors, but not in short-term effects. Regular physical
activity may reduce serum lipid levels and hypertension and increase cardiovascular
fitness,3 all of which could reduce the risk
of vascular dementia and Alzheimer disease.29
Indeed, Rogers and colleagues2 found that active
elderly persons had less decline in cerebral blood flow during a 4-year period
compared with less active elderly persons, a mechanism that might help maintain
cognitive function. Another possible mechanism is that physical activity stimulates
trophic factors and neuronal growth, possibly providing reserve against cognitive
decline and dementia.4, 30 Finally,
it may be that regular exercise is associated with a healthy lifestyle in
general, and although we adjusted for several potential confounders, there
may be other factors associated with healthy behavior in addition to physical
activity that could in turn protect against cognitive decline.
Our study has several limitations. First, our measure of physical activity
is based on a subject's self-report. While it is possible that some subjects
may misreport their level of activity, the Paffenbarger Scale has been shown
to be a reliable measure of physical activity in older women.31
Second, while we used a conservative criterion of cognitive decline, defined
as a 3-point decline or greater on the mMMSE, women did not undergo a clinical
assessment for dementia and we cannot determine the cause of the cognitive
decline. However, our finding of a 20% incidence of cognitive impairment over
8 years is similar to the 2% to 3% annual incidence of dementia reported for
women in this age group.16 Third, there was
some attrition of study subjects between the first cognitive test and testing
that was performed 6 to 8 years later. Women without follow-up were older,
had lower baseline cognitive scores, and had lower baseline physical activity;
exclusion of these subjects could lead to bias. Fourth, while we restricted
our analyses to those without cognitive or physical impairment at baseline,
it is possible that an association between subclinical cognitive impairment
and physical activity level partially explains our results. Finally, most
of the study subjects were white and we cannot conclude whether our findings
would apply to other ethnic groups or to men.
We found that physical activity, even of a moderate degree, was associated
with less risk of cognitive decline in older women followed up for 6 to 8
years. The exact mechanism of this association is not certain, although it
may be related to a healthy lifestyle, a reduction in cardiovascular risk
factors, or a direct effect on neurons. Further research is needed to determine
if physical activity programs could prevent clinically significant cognitive
impairment and if our findings can be replicated in other populations.
AUTHOR INFORMATION
Accepted for publication January 11, 2001.
This study was supported by grants AG05407, AR35582, AG05394, AM35584,
AR35583, and K23-AG00888 from the Public Health Service, Bethesda, Md.
Corresponding author and reprints: Kristine Yaffe, MD, University
of California, San Francisco, Campus Box 111G, 4150 Clement St, San Francisco,
CA 94121 (e-mail: kyaffe{at}itsa.ucsf.edu).
From the Departments of Psychiatry (Dr Yaffe), Neurology (Dr Yaffe),
Epidemiology and Biostatistics (Drs Yaffe and Nevitt and Ms Lui), and Medicine
(Dr Covinsky), University of California, San Francisco; the San Francisco
Veterans Affairs Medical Center, San Francisco, Calif (Drs Yaffe and Covinsky);
and the Department of Public Health and Epidemiology, University of California,
Berkeley (Ms Barnes).
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Dementia Prevention: Methodological Explanations for Inconsistent Results
Coley et al.
Epidemiol Rev 2008;30:35-66.
ABSTRACT
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Walking or vitamin B for cognition in older adults with mild cognitive impairment? A randomised controlled trial
van Uffelen et al.
Br. J. Sports. Med. 2008;42:344-351.
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Nonpharmacological Cognitive Interventions in Aging and Dementia
Acevedo and Loewenstein
J Geriatr Psychiatry Neurol 2007;20:239-249.
ABSTRACT
Associations of Gait Speed and Other Measures of Physical Function With Cognition in a Healthy Cohort of Elderly Persons
Fitzpatrick et al.
Journals of Gerontology Series A: Biological Sciences and Medical Sciences 2007;62:1244-1251.
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Negative Life Events and Cognitive Performance in a Population of Older Adults
Rosnick et al.
J Aging Health 2007;19:612-629.
ABSTRACT
Developing Context and Background Underlying Cognitive Intervention/Training Studies in Older Populations
Elias and Wagster
Journals of Gerontology Series B: Psychological Sciences and Social Science 2007;62:5-10.
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Training and Maintaining Memory Abilities in Healthy Older Adults: Traditional and Novel Approaches
Rebok et al.
Journals of Gerontology Series B: Psychological Sciences and Social Science 2007;62:53-61.
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Language-Enriched Exercise Plus Socialization Slows Cognitive Decline in Alzheimer's Disease
Arkin
AM J ALZHEIMERS DIS OTHER DEMEN 2007;22:62-77.
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Physical activity and risk of Parkinson's disease: a prospective cohort study
Logroscino et al.
J. Neurol. Neurosurg. Psychiatry 2006;77:1318-1322.
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Exercise, cognition, and the aging brain
Kramer et al.
J. Appl. Physiol. 2006;101:1237-1242.
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Secondary prevention of coronary artery disease in elderly persons: a treatise on a report by the american heart association.
Keller and Lemberg
Am J Crit Care 2006;15:514-518.
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Physical activity and behaviour in dementia: A review of the literature and implications for psychosocial intervention in primary care
Eggermont and Scherder
Dementia 2006;5:411-428.
ABSTRACT
From Bedside to Bench: Does Mental and Physical Activity Promote Cognitive Vitality in Late Life?
Studenski et al.
Sci Aging Knowl Environ 2006;2006:pe21-pe21.
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Leisure activity and risk of cognitive impairment: The Chongqing aging study
Wang et al.
Neurology 2006;66:911-913.
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Treating vascular risk factors and maintaining vascular health: Is this the way towards successful cognitive ageing and preventing cognitive decline?
Alagiakrishnan et al.
Postgrad. Med. J. 2006;82:101-105.
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Exercise Is Associated with Reduced Risk for Incident Dementia among Persons 65 Years of Age and Older
Larson et al.
ANN INTERN MED 2006;144:73-81.
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Physical Activity, Cognitive Activity, and Cognitive Decline in a Biracial Community Population
Sturman et al.
Arch Neurol 2005;62:1750-1754.
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Preventive home visits to older people in Southern Sweden
Theander and Edberg
Scand J Public Health 2005;33:392-400.
ABSTRACT
Exercise Enhances Learning and Hippocampal Neurogenesis in Aged Mice
van Praag et al.
J. Neurosci. 2005;25:8680-8685.
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Physical Activity, APOE Genotype, and Dementia Risk: Findings from the Cardiovascular Health Cognition Study
Podewils et al.
Am J Epidemiol 2005;161:639-651.
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Physical activity in relation to cognitive decline in elderly men: The FINE Study
van Gelder et al.
Neurology 2004;63:2316-2321.
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Walking and Dementia in Physically Capable Elderly Men
Abbott et al.
JAMA 2004;292:1447-1453.
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Physical Activity, Including Walking, and Cognitive Function in Older Women
Weuve et al.
JAMA 2004;292:1454-1461.
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Maintaining cognitive health in an ageing society
Butler et al.
The Journal of the Royal Society for the Promotion of Health 2004;124:119-121.
ABSTRACT
Frequency of Going Outdoors: A Predictor of Functional and Psychosocial Change Among Ambulatory Frail Elders Living at Home
Kono et al.
Journals of Gerontology Series A: Biological Sciences and Medical Sciences 2004;59:M275-M280.
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A population-based longitudinal study of cognitive functioning in the menopausal transition
Meyer et al.
Neurology 2003;61:801-806.
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Can Neuromuscular Strength and Function in People With Dementia Be Rehabilitated Using Resistance-Exercise Training? Results From a Preliminary Intervention Study
Thomas and Hageman
Journals of Gerontology Series A: Biological Sciences and Medical Sciences 2003;58:M746-751.
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Achieving and Maintaining Cognitive Vitality With Aging
Fillit et al.
Mayo Clin Proc. 2002;77:681-696.
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Retirement Is No Excuse for Physical Inactivity or Isolation
Keller and Lemberg
Am J Crit Care 2002;11:270-272.
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Physical Activity and Cognitive Decline in Elderly Persons
Pignatti et al.
Arch Intern Med 2002;162:361-362.
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An Obligation for Primary Care Physicians to Prescribe Physical Activity to Sedentary Patients to Reduce the Risk of Chronic Health Conditions
Chakravarthy et al.
Mayo Clin Proc. 2002;77:165-173.
ABSTRACT
Benefits of Physical Activity for Cognitive Function
JWatch Psychiatry 2001;2001:13-13.
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Benefits of Physical Activity for Cognitive Function
Journal Watch Cardiology 2001;2001:12-12.
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Benefits of Physical Activity for Cognitive Function
JWatch General 2001;2001:6-6.
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