From the Department of Neurology (R.L.S., R.G., B.B.-A., D.E.K., W.A.H.,
I-F.L.); Sergievsky Center (R.L.S., W.A.H.); Division of Epidemiology (R.L.S.,
W.A.H., S.S.); Department of Medicine (Division of General Medicine) (S.S.);
and Division of Biostatistics (I-F.L., M.C.P.), Columbia University College of
Physicians and Surgeons and School of Public Health, New York, NY.
Correspondence to Ralph L. Sacco, MD, MS, Neurological Institute, 710 W 168 St, New York, NY 10032. E-mail RLS1{at}Columbia.edu
Methods—The Northern Manhattan Stroke Study is a population-based
incidence and case-control study. Case subjects had first
ischemic stroke, and control subjects were derived through
random-digit dialing with 1:2 matching for age, sex, and
race/ethnicity. Physical activity was recorded through a
standardized in-person interview regarding the frequency and duration
of 14 activities over the 2 prior weeks. Conditional logistic
regression was used to calculate odds ratios (OR) and 95%
confidence intervals after adjustment for medical and socioeconomic
confounders.
Results—Over 30 months, 369 case subjects and 678 control
subjects were enrolled. Mean age was 69.9±12 years; 57% were women,
18% whites, 30% blacks, and 52% Hispanics. Leisure-time physical
activity was significantly protective for stroke after adjustment for
cardiac disease, peripheral vascular disease, hypertension,
diabetes, smoking, alcohol use, obesity, medical reasons for limited
activity, education, and season of enrollment (OR=0.37; 95% confidence
interval=0.25 to 0.55). The protective effect of physical activity was
detected in both younger and older groups, in men and women, and in
whites, blacks, and Hispanics. A dose-response relationship was shown
for both intensity (light-moderate activity OR=0.39; heavy OR=0.23) and
duration (<2 h/wk OR=0.42; 2 to <5 h/wk OR=0.35;
Conclusions—Leisure-time physical activity was related to a
decreased occurrence of ischemic stroke in our elderly,
multiethnic, urban subjects. More emphasis on physical activity in
stroke prevention campaigns is needed among the elderly.
The relationship between physical activity and stroke is less well
studied than for other cardiovascular diseases. Only a
few previous studies have evaluated the association between physical
activity and the risk of stroke.4 5 6 7 8 9 10 11 12 The
beneficial effects have been predominately described among white
populations, have been more apparent for men than women, and generally
have been described for younger rather than older adults. The aim of
this population-based case-control study was to investigate the
relationship between leisure-time/recreational physical activity and
ischemic stroke in an elderly, urban, multiethnic
population.
Selection of Case Subjects
Patients diagnosed with stroke as well as a variety of other
neurological syndromes (eg, aphasia, hemiparesis, weakness, coma,
syncope) were screened by the research assistants, and the case was
discussed with a study neurologist to confirm eligibility. After
permission was received from the attending physician, written informed
consent was obtained from the patient or the family. The study was
approved by the institutional review boards at Columbia-Presbyterian
Medical Center and the other primary hospitals.
Selection of Control Subjects
The interview data from control-eligible subjects were downloaded to
the NOMASS computer system and sorted by sex and race/ethnicity. These
subjects were recontacted by the NOMASS staff and invited to
participate in the study. Appointments were made for in-person
evaluations at the hospital or home for those who could not come in
person (7% were done at home). Two concurrent control subjects were
randomly selected from among the participants within the appropriate
stratum and matched to each stroke case subject by age (within 5 years
in either direction), sex, and race/ethnicity. Our telephone survey
response rate was 94%, and our in-person participation rate was 70%
among the telephone responders. At the time of the in-person visit,
written informed consent was obtained.
Index Evaluation of Case and Control Subjects
All assessments were conducted in English or Spanish depending on the
primary language of the participant. Race/ethnicity was based on
self-identification through a series of interview questions modeled
after the US census. All participants responding affirmatively to being
of Spanish origin or identifying themselves as Hispanic were classified
as such. All participants classifying themselves as white without any
Hispanic origin or black without any Hispanic origin were classified as
white, non-Hispanic, or black, non-Hispanic, respectively.
Subjects were interviewed regarding sociodemographic characteristics,
stroke risk factors, and other medical conditions. Standardized
questions were adapted from the Behavioral Risk Factor Surveillance
System by the Centers for Disease Control and Prevention regarding the
following conditions: hypertension, diabetes,
hypercholesterolemia, peripheral
vascular disease, transient ischemic attack, cigarette smoking,
alcohol use, and cardiac conditions such as myocardial infarction,
coronary artery disease, angina, congestive heart failure,
atrial fibrillation, other arrhythmias, and valvular
heart disease.16 Subjects also completed a
comprehensive functional status battery, which included the Barthel
ADL, the QWB , and the Geriatric Social Readjustment Rating
scales.17 18 19
Blood pressure was measured with the use of a calibrated standard
aneroid sphygmomanometer (Omron). After the subject had 5 minutes of
relative immobility in a sitting position, two blood pressure
measurements separated by 15 minutes were recorded. In subjects
with blood pressure recordings discrepant by >10 mm Hg,
a third measurement was obtained by the study physician and entered
into the database along with the closer blood pressure reading by the
research assistant. Anthropometric measurements of height and weight
were determined by the use of calibrated scales. Blood samples were
sent for complete blood count on admission or enrollment. Fasting
glucose was measured with a Hitachi 747 automated spectrometer
(Boehringer). Fasting lipid panels (including total
cholesterol, LDL, HDL, and triglyceride) were
measured with a Hitachi 705 automated spectrometer
(Boehringer).
Hypertension was defined as a systolic blood pressure
recording
Physical Activity Assessment
Statistical Analyses
Subgroup analyses were performed to evaluate for any
confounding due to recent infection or TIA preceding the stroke. Proxy
reliability of the physical activity questionnaire was assessed among
16 stroke case subjects and their proxies. After historical information
from the patient was obtained in the usual manner, a surrogate familiar
with the patient's medical history and habits, but not aware of
his/her responses to the questionnaire, was interviewed with the same
instrument. To evaluate whether using the proxy variable led to any
bias in estimates of the ORs, a subgroup analysis was done
restricting the data to only nonproxy physical activity data.
Construct validity of our physical activity assessment was demonstrated
within our cohort. Physical activity duration measurement correlated
inversely with BMI among the control subjects (Pearson's
r=-.125; P<.001) and directly with ADL scores
(Pearson's r=.157; P<.0001) and other activity
questions on the QWB scale (Pearson's r=.182;
P<.0001). A seasonal variation in the performance
of physical activity was observed. Our control subjects were more
active during nonwinter (March 21 to December 20) than winter months
(December 21 to March 20) (P<.0005). The physical activity
assessment was reasonably reliable when obtained from proxies, with a
crude concordance rate of 0.69 for engaging in any physical activity in
our proxy reliability substudy.
During the 2 weeks before study enrollment, 49% of case subjects and
25% of control subjects reported no leisure-time recreational physical
activity (Table 2
Engaging in any physical activity (light-moderate or heavy) was
independently related to a reduced risk of stroke (OR=0.37; 95%
CI=0.25 to 0.55) after adjustment for hypertension, diabetes, cardiac
disease, peripheral vascular disease, smoking, obesity,
heavy alcohol use, medical reasons for limited activity, education, and
season of enrollment. The protective effect of exercise for stroke was
demonstrated in all subgroups after stratification by age, sex, and
race/ethnicity (Fig 1
To assess for other confounding factors that may have affected the
level of physical activity in our study subjects, we performed several
analyses. The effect of physical activity was similar in our
subgroup analysis restricted to nonproxy data (OR=.40). After
exclusion of case subjects who experienced TIA during the preceding 30
days, the adjusted OR for physical activity was comparable to our
original model (OR=0.42; 95% CI=0.28 to 0.63). Symptoms of infection
were reported in only 9% of our case subjects and 6% of our control
subjects and were not statistically different, and the association
between physical activity and stroke remained even after adjustment for
admission white blood cell count (OR=0.36; 95% CI=0.22 to 0.60). The
median prestroke or preenrollment Barthel ADL scores were 100 for both
our case and control subjects, and the mean QWB scores were similar
between case subjects (0.7±0.14) and control subjects (0.7±0.16)
(Table 1
When we used the no-exercise group as a reference, heavy activity
(OR=0.23; CI=0.10 to 0.54) appeared slightly more protective than
light-moderate activity (OR=0.39; CI=0.26 to 0.58), suggesting a
dose-response relationship between the intensity of physical activity
and stroke. The same dose-response relationship was seen for duration
of physical activity, with the greatest protection seen in those
performing
The protective effect of physical activity in our subjects was not
fully explained by elevation in HDL levels. Mean plasma HDL levels were
not related to leisure-time physical activity, and the independent
effect of physical activity remained after HDL was added to our model
in an analysis among the 954 subjects (91% of study sample)
with HDL data. Moreover, the effect of physical activity was not
altered by other lipid levels, including fasting
cholesterol, triglyceride, or LDL. Although the
mean diastolic blood pressure level was slightly lower
among physically active compared with inactive control subjects, the
protective effects of physical activity were also independent of
hypertension and other stroke risk factors. Furthermore, the protective
effect did not differ by risk factor strata for hypertension, diabetes,
any cardiac disease, or smoking status, and no significant interactions
were detected between physical activity and the covariates in the
multivariate analyses.
In our study we detected a beneficial relationship between leisure-time
physical activity and stroke. The protective effects were found after
adjustment for medical and socioeconomic confounders, season of
recruitment, and smoking and alcohol use. Similar benefits were
observed for those younger and older than 65 years, both men and women,
and among whites, blacks, and Hispanics. The mean duration of
leisure-time physical activity in our population approximated that
recommended by the Centers for Disease Control and National Institutes
of Health, with much less participation in heavy forms of activity. In
our relatively older cohort, walking was the most common form of
recreational physical activity reported, which is consistent
with observations in other comparably aged
populations.21 25 The finding of an overall
protective effect for leisure-time physical activity suggests that even
light-moderate forms of activity may confer some benefits for the
elderly. Our results are particularly relevant in the more sedentary
and older population who have a greater risk of stroke and more
prevalent cardiovascular risk factors and whose
physical activity pattern may comprise mainly light to moderate
activity of shorter duration.
The protective effects of physical activity for stroke risk noted in
other studies were limited to certain age, sex, and risk factor
subgroups. The Honolulu Heart Program, which investigated older
middle-aged men of Japanese ancestry, showed a protective effect of
habitual physical activity from thromboembolic stroke only among their
nonsmoking group.5 The Framingham Study
demonstrated the benefits of combined leisure and work physical
activities for men but not for women.6 In the
Oslo Study of men aged 40 to 49 years, increased leisure physical
activity was related to a reduced stroke
incidence.7 For women aged 40 to 65 years, the
Nurses' Health Study showed an inverse association between level of
physical activity and the incidence of any
stroke.8 For white, lower and middle class, urban
women participating in the Copenhagen City Heart Study, lack of
physical activity had an effect similar to that of cigarette smoking,
with a relative risk of stroke of 1.4.9 In the
National Health and Nutrition Examination Survey I follow-up study, low
level of recreational or nonrecreational activities was slightly
associated with an increased risk of stroke for both men and women and
among blacks.10
The dose-response relationship between level and duration of leisure
physical activity and protective effects from stroke was
consistent in our study population and among each of the age,
sex, and race/ethnic subgroups. Although performance of
leisure-time physical activities conferred protection, more vigorous
(heavy) forms of physical activities provided additional benefits
compared with light-moderate activities. The same was true for duration
of physical activity. Although the odds of stroke were reduced in the
group performing <2 h/wk of physical activity, additional protection
was observed with increasing duration of exercise. The beneficial
effects of even small amounts of leisure-time physical activity in the
older population have not been reported previously, and the
dose-response relationship is encouraging for those individuals who can
safely increase their level of physical activity.
The dose-response relationship between increasing amounts of physical
activity and the reduction in the risk of stroke has not always been
demonstrated. Wannamethee and Shaper11 found an
inverse relationship between physical activity and risk of stroke, but
the benefit of vigorous physical activity for stroke was offset by an
increased risk of heart attack. In Framingham among the older cohort,
the strongest protective effect was detected in the medium tertile
physical activity subgroup, with no additional benefit gained from
higher levels of physical activity.6 Among
subjects in a case-control study in West Birmingham, UK, who were free
of cardiac disease, peripheral vascular disease, and poor
health, recent vigorous exercise was no more protective than
walking.12
The protective effect of physical activity may be partly mediated
through its role in controlling various known risk factors for stroke.
Exercise has been shown to lower blood pressure in certain
groups.26 27 28 It is also associated with a lower
incidence of cardiovascular
disease,29 30 31 32 improved diabetes
control,33 34 better dietary habits, and lower
body weight.35 36 Cigarette smokers are less
likely to participate in exercise programs.37
Furthermore, people with a higher level of education participate in
more leisure-time activity.38 The finding of an
independent effect of physical activity after adjustment for these
factors suggests that mechanisms other than the control of risk factors
may be responsible for the protective effect of physical activity for
stroke.
Other biological mechanisms are also associated with physical activity,
including reductions in plasma fibrinogen and platelet activity and
elevations in plasma tissue plasminogen
activator activity and HDL
concentrations.39 40 41 42 In a preliminary
analysis from our multiethnic population, we found HDL
concentration to be inversely related to the risk of
stroke.43 However, we found no significant
differences in plasma HDL levels among our inactive, light-moderately
active, and heavily active groups in either our case or control
subjects, and the independent effect of physical activity remained
after HDL and other lipid levels were added to our model in a subgroup
analysis.
There are some limitations to our study. Our design was a case-control
study and not a prospective cohort study. However, our subjects were
population based, and selection bias is less likely than in
hospital-based case-control studies. The OR more closely approximates a
relative risk in population-based case-control studies, since the case
and control subjects are derived from the same community and provide a
close approximation of the prevalence of exposure in those with and
without incident disease.44 Recall bias, a
frequent source of bias in case-control studies, seems less likely
since the case and control subjects were not aware of the hypotheses
being tested. In addition, recall physical activity surveys like the
instrument we used are less likely to influence a subject's typical
behavior than activity diaries or logs.22
There may have been some unmeasured confounders that led to a reduction
in recent physical activity among the stroke case subjects or
influenced the selection of control subjects who were more physically
active. This could have resulted in an overestimation of the OR.
However, we made a concerted effort to adjust for such confounders in
our analyses and performed nonresponse analyses which
showed that the control subjects who participated in the study had risk
factor profiles similar to those who did not participate in person,
except for greater BMI and smoking among the participants. Both of
these conditions would lead to bias of the OR toward the null value,
since such conditions would decrease the likelihood of engaging in
physical activity. Some have argued that recent infections are more
frequent in stroke patients,45 46 which could
also confound the physical activity association. We found no direct
association between clinical symptoms of infection and physical
activity among our case subjects, and our findings were the same even
after we controlled for admission white blood cell count. There was
likewise no relationship between occurrence of TIA within 30 days
before stroke and physical activity to suggest that TIA differentially
reduced the level of physical activity in our case subjects.
Furthermore, the prestroke or preenrollment median ADL scores, mean QWB
scores, and Geriatric Social Readjustment Scale assessments were
similar among our case and control subjects.
Physical activity questionnaires have differed in the time frame of
assessment, and some have included occupational as well as leisure or
recreational activities.47 48 49 50 51 52 53 54 55 The majority of
our subjects were elderly, with only 16% working at the time of
enrollment. Among those who were working, the job types infrequently
involved strenuous physical activities. Our physical activity
assessments were not designed to evaluate lifelong exercise practices,
exercise patterns at younger ages, physical conditioning, or
quantitative estimations of energy expenditure. Our instrument measured
leisure physical activity during the preceding 2 weeks. The 2-week
period of activity recall was deemed reliable, short enough to allow
reasonably accurate recall in an elderly sample, yet long enough to
represent the usual activity patterns of most
people.55 The inverse correlation of physical
activity with BMI in our study could argue for our measurements being
correlated with more sustained patterns of physical activity. It is not
clear from our study whether the pattern of physical activity in the
elderly correlated with a life-long pattern of physical activity that
conferred the protective effect or whether recent physical activity,
regardless of life-long patterns, can confer some benefits.
Our study demonstrates the importance of leisure-time physical activity
in the prevention of stroke among the elderly, in men and women, and in
all race/ethnic groups. While currently available methods of physical
activity measurement may not be ideal, they have provided a means of
demonstrating important benefits of physical
activity.22 The benefits in stroke are apparent
even for light-moderate activities, such as walking, and the data
support additional benefits to be gained from increasing the level and
duration of one's recreational activity. The potential undesirable
consequences of extreme exercise, such as alterations in hormonal
levels in women, musculoskeletal injuries, loss of bone mineral
content, and risk of acute myocardial
infarction,56 57 58 59 60 61 62 should be considered when
advising individual patients, particularly the elderly, to increase
their physical activity. Nevertheless, physical activity is a
modifiable behavior that requires greater emphasis in stroke prevention
campaigns. As long as the adverse effects of high-intensity physical
activity are minimized, leisure-time physical activity could translate
into a cost-effective means of decreasing the public health burden of
stroke and other cardiovascular diseases among our
rapidly aging population.
Received September 17, 1997;
revision received November 6, 1997;
accepted November 21, 1997.
© 1998 American Heart Association, Inc.
Original Contributions
Leisure-Time Physical Activity and Ischemic Stroke Risk
The Northern Manhattan Stroke Study
Abstract
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
Background and Purpose—Physical
activity reduces the risk of premature death and
cardiovascular disease, but the relationship to stroke
is less well studied. The objective of this study was to investigate
the association between leisure-time physical activity and
ischemic stroke in an urban, elderly, multiethnic
population. 
5 h/wk OR=0.31) of
physical activity.
Key Words: cerebrovascular disorders • elderly • epidemiology • ethnic groups • racial differences • risk factors
Introduction
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
Regular exercise has
well-established benefits for reducing the risk of premature death and
many diseases, including cardiovascular disease. In
Healthy People 2000, the US Department of Health and Human
Services targeted physical activity in health objectives 1.3 to 1.7 for
health promotion and disease prevention. The aim by the year 2000 is to
increase the proportion of people who engage in regular physical
activity and reduce the proportion of those who engage in no
leisure-time physical activity, particularly among people aged 65 years
and older.1 Current guidelines endorsed by the
Centers for Disease Control and Prevention and the National Institutes
of Health recommend that Americans should exercise for at least 30
minutes of moderately intense physical activity on most, and preferably
all, days of the week.2 3
Subjects and Methods
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
The Northern Manhattan Stroke Study (NOMASS) is an ongoing,
prospective, population-based incidence and case-control study designed
to determine stroke incidence, risk factors, and prognosis in a
multiethnic, urban population. Northern Manhattan consists of the area
north of 145th Street and south of 218th Street, bordered on the west
by the Hudson River, and separated from the Bronx on the east by the
Harlem River. In 1990 nearly 260 000 people lived in the region, with
40% older than 39 years. The racial/ethnic distribution in this
community is approximately 20% black, 63% Hispanic, and 15% white
residents.
Case subjects eligible for the case-control study were
prospectively enrolled if they met the following criteria: (1)
diagnosed with first cerebral infarction after July 1, 1993; (2) older
than 39 years at onset of the stroke; and (3) resided in the Northern
Manhattan community in a household with a telephone. Even patients who
died from their initial stroke were enrolled by relying on surrogate
data. Patients with TIA were excluded, ie, neurological deficits
lasting less than 24 hours and no ischemic infarct found on
brain imaging. Prospective case surveillance consisted of daily
screening of all admissions, discharges, and head CT scan logs at the
Presbyterian Hospital in the City of New York, the only hospital in the
community where approximately 80% of all patients in Northern
Manhattan with cerebral infarction are
hospitalized.13 To ensure complete incident
stroke enumeration in the region, cases with International
Classification of Diseases, 9th revision codes 430 to 438, 446,
and 447 were also identified through discharge lists from 14 hospitals
outside the immediate region. Extensive ongoing community-based
surveillance for nonhospitalized stroke was done through random
household telephone surveys (Audit and Survey, Inc) and frequent
interval contacts with community physicians, senior citizen centers,
visiting nurse services, and other social and cultural community
agencies. Direct community outreach strategies and the local media were
also utilized to encourage self-referral of patients with stroke.
Community control subjects were eligible if they (1) had never
been diagnosed with a stroke, (2) were older than 39 years, and (3)
resided in Northern Manhattan for at least 3 months in a household with
a telephone. Stroke-free subjects were identified by random-digit
dialing with dual-frame sampling to identify both published and
unpublished telephone numbers.14 15 When a
household was contacted, the research objectives were explained, and a
resident older than 39 years was interviewed briefly to record age,
sex, race/ethnicity, and biobehavioral and vascular disease risk
factors. The telephone interviews were conducted by Audits and Surveys,
Inc, a survey research firm that used trained interviewers bilingual in
English and Spanish.
Data were collected through interview of the case and control
subjects by trained research assistants, review of the medical
records, physical and neurological examination by the study
physicians, in-person measurements, and fasting blood specimens for
lipid and glucose measurements. Data were obtained directly from study
subjects by means of standardized data collection instruments. When the
subject was unable to answer questions because of death, aphasia, coma,
dementia, or other conditions, a proxy who was knowledgeable about the
patient's history was interviewed (data were obtained from the study
subject in 74% of case subjects). Stroke-free control subjects were
interviewed in person and evaluated in the same manner as case subjects
(data were obtained from the study subject in 99% of control
subjects). Case subjects were interviewed as soon as possible after
their stroke, within a median time of 4 days from stroke onset. 160 mm Hg or a diastolic blood
pressure recording 95 mm Hg (based on the average of
the two blood pressure measurements) or the patient's self-report of a
history of hypertension or antihypertensive use. Diabetes mellitus was
defined by a fasting glucose >140 mg/dL (7.7 mmol/L), the
patient's self-report of such a history, or insulin or hypoglycemic
use. For this analysis, smoking was defined as currently
smoking cigarettes, and heavy alcohol use was defined as current
drinking of 14 drinks per week. BMI was calculated as weight
(kilograms) divided by height (meters) squared, and obesity was defined
as BMI 27.8 for men and 27.3 for women.1
A questionnaire adapted from the National Health Interview
Survey of the National Center for Health Statistics was used to measure
recent leisure-time/recreational physical
activities.20 This survey form has been found to
be reliable in evaluating elderly subjects.21 The
questionnaire records the frequency and duration of 14 different
recreational activities during the 2-week period before the interview.
In light of the US Surgeon General's report on physical activity and
health,2 22 activities surveyed in our elderly
population were classified as light-moderate (walking, calisthenics,
dancing, golf, bowling, horseback riding, and gardening) and heavy
(hiking, tennis, swimming, bicycle riding, jogging, aerobic dancing,
and handball or racquetball or squash). A series of yes/no responses
were recorded for each of the questions, posed as "In the last 2
weeks, have you engaged in for physical
activity?" For stroke case subjects, the question was phrased as
"In the last 2 weeks prior to your stroke . . . ." Each
affirmative response was followed by two other questions: "On
average, how many times did you perform this activity over the last 2
weeks?" and "On average, how many minutes each time?" From these
responses the frequency and duration of each activity were
computed.
The crude frequency and mean duration of any physical
activities, as well as the individual physical activities and their
subgroups (light-moderate and heavy), were examined in the case and
control subjects. Multivariate conditional logistic
regression for matched data was used to calculate the ORs and 95% CIs
for physical activity and stroke, with adjustment for potential stroke
risk factors such as hypertension, diabetes, cardiac disease, smoking,
heavy alcohol use, and obesity, education, and season (winter versus
other seasons). The latter was done to control for any seasonal
mismatch between the case and control subjects, since subjects enrolled
in winter may be less physically active. Adjusted analyses were
performed overall and stratified by age (<65 and 65 years), sex, and
race/ethnicity. To examine for a dose-response relationship, physical
activity was categorized by level of intensity into three groups (none,
light-moderate, and heavy activities) and by duration of physical
activity (none, <2 h/wk, 2 to <5 h/wk, and 5 h/wk). Subjects
performing both light-moderate and heavy activities were classified as
heavy. We assessed for a linear trend in duration as a continuous
variable by testing whether the coefficient of the quadratic term
was zero. Interactions between any physical activity and other stroke
risk factors were assessed in the multivariate
model.
Results
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
From July 1, 1993, to December 31, 1995, 369 case subjects with
first cerebral infarction and 678 age-, sex-, and
race/ethnicity-matched control subjects were enrolled in the
case-control study. Among the case subjects, 7% died within 30 days of
the stroke, and both fatal and nonfatal strokes were included in the
analyses. Overall, there were 18% whites, 30% blacks, and
52% Hispanics. Mean age was 69.9±12 years, and women constituted
57%. Hypertension, diabetes, peripheral vascular disease,
smoking, and cardiac disease were more common among the case subjects,
while obesity was more prevalent among the control subjects. The
control subjects were slightly more educated and were enrolled slightly
more frequently during nonwinter months than the case subjects (Table 1
). Only 16% of the case and control
subjects were working >10 h/wk at the time of enrollment. Based on the
recruitment telephone-interview data, our nonresponse analysis
showed that control subjects who participated in person had a similar
frequency of hypertension, diabetes, and cardiac disease but were more
likely to be overweight and smoke cigarettes than subjects who did not
participate.
View this table:
[in a new window]
Table 1. Demographics and Vascular Risk Factors ). Among those who
performed any physical activity, walking was the most frequently
reported form of exercise in both case and control subjects, followed
by calisthenics. The mean duration for any activity was 4.0±4.4 h/wk
for case subjects and 4.7±4.8 h/wk for control subjects. As expected
in this elderly sample, the mean duration of the heavy types of
physical activity was less than the light-moderate forms of
activity.
View this table:
[in a new window]
Table 2. Intensity and Duration of Physical Activities ). Our smaller white
subgroup had the widest CI in the adjusted multivariate
analyses; however, the point estimate of the OR for physical
activity was still in the protective direction.
View larger version (32K):
[in a new window]
Figure 1. Association between physical activity and stroke.
Adjusted ORs and 95% CIs from multivariate conditional
logistic regression analysis of the association between
ischemic stroke and physical activity are shown overall and
stratified by age, sex, and race/ethnicity. No physical activity is the
reference category within each stratum. 
). With the use of the Geriatric Social Readjustment Rating
Scale to survey recent changes in the subjects' life events that may
affect physical activity, the case and control groups were identical
when we compared "stressful physical illness" (painful arthritis,
eyesight failure, hearing failure, or feeling of slowing down) and
"impactful acute loss events" (death of spouse, death of close
friend, death of relative, or loss of job). 5 h/wk of exercise (Fig 2).
Test for linear trend of the dose response for physical activity
duration was significant (P=.006), indicating that every
unit increment in duration of physical activity was associated with a
significant decrement in stroke risk. The dose-response relationships
were also observed for each of the age, sex, and race/ethnicity
strata.
View larger version (40K):
[in a new window]
Figure 2. Dose-response relationship between physical
activity and stroke. ORs and 95% CIs from multivariate
conditional logistic regression analysis of the association
between ischemic stroke and physical activity are shown
stratified by intensity of activity and duration in hours per week.
Mod/Hvy indicates moderate-heavy activity.
Discussion
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
The cardiovascular benefits of physical activity
have been emphasized by numerous organizations, including the Centers
for Disease Control, National Institutes of Health, and the American
Heart Association. Recent guidelines recommended that individuals
perform moderate exercise for approximately 3.5 h/wk. This suggestion
arose from accumulating data regarding the beneficial effects of
physical activity in reducing the incidence of heart disease. The
benefits for stroke, however, have not always been consistent
across age and sex subgroups. Furthermore, little is known about
physical activity in different nonwhite race/ethnic groups, in whom the
stroke burden has been reported to be
greater.23 24
Selected Abbreviations and Acronyms
ADL
=
Activities of Daily Living
BMI
=
body mass index
CI
=
confidence interval
NOMASS
=
Northern Manhattan Stroke Study
OR
=
odds ratio
QWB
=
Quality of Well-being
TIA
=
transient ischemic attack
Acknowledgments
This study was supported by grants from the National Institute
of Neurological Disorders and Stroke (R01 NS 27517, R01 NS 29993, and
T32 NS 07153) and the General Clinical Research Center (2 M01 RR00645).
We acknowledge the support of Dr J.P. Mohr, Director of Cerebrovascular
Research; the statistical assistance of Qiong Gu; the processing of the
lipids by Drs Henry Ginsberg and Lars F. Berglund in the Division of
Preventive Medicine and Nutrition and the Irving Center for Clinical
Research; and the help provided by Drs J. Kirk Roberts and Mitchell S.
Elkind, fellows in stroke and neuroepidemiology.
Footnotes
Presented in part in abstract form at the 48th Annual Meeting of the American Academy of Neurology, San Francisco, Calif, March 23–30, 1996.
References
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
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