J Ch Epiddol Vol. 41, No. 8, pp. 719-726, 1988 Printed in Great Britain

0895-4356/88 S3.00 + 0.00 Pergamon Press plc

THE FRAMINGHAM DISABILITY STUDY: PHYSICAL DISABILITY AMONG COMMUNITY-DWELLING

SURVIVORS OF STROKE

ALAN M. JE?TE,‘** JOAN L. PINSKY,’ LAURENCE G. BRANCH,~ PHILIP A. WOLF“ and MANNING FEW&E&

‘MGH Institute of Health Professions, Massachusetts General Hospital, Boston, MA 02108, 2Division of Epidemiology and Clinical Applications, National Heart, Lung and Blood Institute, Bethesda, Md, ‘Boston University School of Public Health, Boston, Mass., GRECC, Bedford, VA Hospital, Bedford, Mass., 4Boston University Medical Center, Boston, Mass. and 5National Center

for Health Statistics, Hyattsville, Md, U.S.A.

(Received in revised form 2 March 1988)

Ahatract-The relationship between stroke and physical disability was examined in a cohort of adult, Framingham, Massachusetts, residents who, between 1948 and 1951, were assembled for a longitudinal examination of cardiovascular disease. Multivariate analyses examined the amount of residual disability attributable to stroke among 2540 community-dwelling survivors, 27 years after their initial examination, after controlling for age, cardiovascular risk factors, other cardiovascular diseases, and eight general health conditions.related to physical disability. Among men living in the community, a history of stroke explained 12% of the variance in physical disability. Suffering a stroke, however, was not as strongly related to physical disability among women living in the community, accounting for only 3% of the variance. Results suggest that although older men and women die from the same major causes, they may not be disabled by the same conditions.

Cardiovascular diseases Stroke Disability

INTRODUCTION

Older men and women die from the same major causes [l]. Cerebral vascular disease (stroke) is ranked third behind heart disease and cancer as a cause of death for both sexes, even though rates of stroke are higher among men than women [2]. Over the past decade we have wit- nessed rapidly declining age-specific mortality rates for both sexes [3]. This improvement is attributable to a decrease in the risk of death from heart disease and cerebral vascular disease (41. Reasons for this decline are not fully known. Most likely, it is due to the combined

*Renrint reouests should be addressed to: Alan M. Jette, MGH Institute of Health Professions, Massachusetts General Hosoital. Boston. MA 02108-3402, U.S.A.

This research Gas supports in part by contracts from the National Heart, Lung and Blood Institute (NolHV52971) and by funds from the National Institute on Aging.

effects of several factors: better control of major risk factors such as hypertension; changes in diet, smoking, exercise and other health be- haviours; and earlier diagnosis and improved treatment [5].

Declining mortality rates among the elderly heightens awareness of the health profile of this growing cohort of survivors of major life- threatening diseases [6]. Better information is needed on the major determinants of disability among survivors of major chronic diseases as U.S. society begins to explore ways of reducing and preventing physical disability among its aging population. The Framingham Disability Study (FDS) presents an opportunity to con- duct longitudinal investigations into key factors that may contribute to physical disability among the community-dwelling aged. In this paper, we examine the extent to which a history of stroke is related to residual physical disability

719

720 ALAN M. JJZRI et al.

among community-dwelling survivors and ex- plore the degree to which elderly men and women experience a similar functional prog- nosis following a stroke.

METHOJIS

Between 1948 and 1951 the Framingham Study assembled a cohort of 5209 persons, aged 28-62 in Framingham, Massachusetts [7’J. Infor- mation on potential cardiovascular disease risk factors and disease endpoints was obtained every 2 years by interview, physical examina- tion, and laboratory tests. By December 1979, 31 years after the inception of the study, the fifteenth examination cycle had been completed.

The Framingham Disability Study was de- signed to yield a quantitative assessment of, levels of physical and social disability baseg on respondents’ self-reported information. Com- munity-dwelling members of the Framingham Study were interviewed from September 1976 (midway through the fourteenth examination cycle) through November 1978 (midway through the fifteenth examination cycle). This time period will be referred to throughout this report as examination 14/15. FDS participants reported current level of function at the time of examination 14/15. Descriptions of the prevalence findings on physical and social disability from this study have been reported elsewhere [8,9].

Sample

At the time the FDS interviewing began, 1649 of the original cohort of 5209 had died, 218 had moved away and dropped out of the study, 15 1 had refused to return for examination, and 354 had been missing from the study foi no known reasons for the last 5 years. Members of the original cohort who were alive at the time but did not participate in the FDS were significantly more likely to be female (65.3 vs 58.9%), older (mean age = 44.0 vs 40.9 years), and have a higher mean systolic blood pressure (135.2 vs 131.2mmHg), (p f 0.01 based on Chi square analysis.) The non?participants did not differ from participants with respect to mean body mass and mean number of cigarettes smoked.

Of the remaining 2837 individuals, 183 (6%) were not included in this sample of FDS partici- pants: 4 1 were nursing home residents who were unable to come to the clinic and were therefore

excluded; 87 had come into the clinic for their 14th examination before the disability inter- viewing began and had not come in for their 15th examination by the time the disability interviewing ended; 43 refused to be inter- viewed; 11 came for their physical examination but were missed by the disability interviewer due to scheduling difficulties and were unable to be rescheduled, and 1 person died before a re- scheduled interview was taken.

One hundred and fourteen (4%) of the 2654 FDS participants eligible for this analysis were excluded for the following reasons; 2 persons had missing values in all three components of the cumulative disability index, 40 had missing values in other key variables examined in this analysis, and 72 persons did not fit the Guttman model used in creating the cumulative disability index. Those who did not fit the Guttman model were significantly more likely to be male, have intermittent claudication or diabetes (p < 0.05 based on Chi square analysis). Reanalyzing the data with assigned cumulative disability index values for these 72 persons had no effect on the results.

Table 1 displays demographic information on the 2540 FDS women and men living in the community available for this investigation. Age and marital status were determined at examina- tion 14/15; level of education attainment was assessed at examination 1. Ages ranged from 56 to 88 years for the women and from 56 to 86 years for the men. Compared to their male counterparts, the women were slightly older,

Table 1. Per cent distribution of men and women at examination 14/U by age, marital status and education

(Framingham Disability Study, 1976-1978)

Percent

Age (Yr)* 56-64 65-74 75-88

Marital status* Never married Married Widowed Divorced/separated

Education 8 years or less Some high school High school paduate Beyond high school

*p c 0.01.

Women

37.3 39.9 22.8

(n = 1504)

9.5 52.8 33.4

(n =4.k4)

24.1 11.9 32.8 31.2

(n = 1467)

Mell

45.6 36.5 18.0

(n = 1036)

3.4 86.1 8.4

(n =t36)

21.8 16.5. 31.0

(n q&o)

The Framingham Disability Study 721

more likely to be widowed, and had a similar pattern of formal educational attainment.

DEFINITION OF VARIABLES

Cumulative disability index (CDZ)

All physical disability questions were adapted from previous work. Four items were drawn from the Katz Activities of Daily Living (ADL), scale [lo], two came from Branch’s work [ll], three items came from the Rosow and Breslau Health scale [12], and nine measures of physical performance were developed by Nagi [13]. All items have been widely used in community studies of this nature [14, 151.

The CD1 was derived from responses to 18 questionnaire items. The initial step was to dichotomize the response to each item into a disabled or non-disabled category. We then constructed three subscales: a Basic ADL scale (including the Katz and Branch items), a Gross Mobility Functional Health scale (the Rosow and Breslau items), and Nagi’s Physical Perfor- mance scale. Subscale scores were then dichoto- mized into disabled or non-disabled categories. The subscale definitions are presented in Table 2.

Table 2. Values of cumulative disability index and compo- nent scales used in the Framingham Disability Study,

1976-1978

Cumulative Component scales disability

index Nagi* Rosow-Breslaut Modified Katz1

0 0 0 0 1 1 0 0 2 1 1 0 3 1 1 1

*Co&s for Nagi scale. 0 = reports performing all of the following activities without difficulty: (a) pulling or push- ing a large object; (b) stooping, crouching or kneeling; (c) lifting or carrying weights under 10 lb (4.5 kg); (d) lifting or carrying weights over 10 lb (4.5 kg); (3) reaching or extending arms below shoulder level; (f) reaching or ex- tending arms above shoulder level; (g) writing, handling or fingering small objects; (h) standing in one place for long periods, say 15 mm; (i) sitting for long periods, say 1 hr. 1 = reports performing one or more of the above-men- tioned activities with difficulty.

tCo&s for Rosow-Breslau scale. 0 = reports is able to do all of the following activities without help: (a) heavy work around the house; (b) walk up and down stairs; (c) walk half a mile. 1 = reports is not able to do one or more of the above-mentioned activities without help.

$Codes for Mod@ed Katz scale. 0 = reports does not need help in any of the following activities: (a) walking across a small room; (b) bathing; (c) personal grooming; (d) dressing; (e) eating; (f) getting from a bed to a chair. 1 = reports needs help in one or more of the above-men- tioned activities.

Persons with missing data (n = 319) in one or two of the subscales were assigned subscale values in the following manner. Each person in this group was randomly paired with a person who had a similar configuration of values in the scale(s) of his or her counterpart identified in the random pairing procedure. For example, a group of 101 persons (group A) were identified as having a missing score in the Nagi scale, a Rosow’ score of 0, and a Katz score of 0. After randomly ordering the 1832 persons without missing values in the subscales, the first 101 (group B) who had Rosow scores of 0 and modified Katz scores of 0 were identified. Each of the 101 persons in group A was assigned a Nagi score of that person’s counterpart in group B. This procedure was repeated for 15 other configurations of missing and non-missing val- ues. Those with missing values in one or more subscales were more likely to be older, female, have had a stroke, intermittent claudication, coronary heart disease or diabetes (p < 0.05 based on Chi square analysis). Excluding those participants with imputed values had no effect on the results.

The three subscales were then combined into a unidimensional cumulative disability index. The CD1 is the Guttman scale which ranges from 0 to 3, in which 0 equals no disability in each of the three subscales, 1 equals disability in the Nagi scale only, 2 equals disability in the Nagi and Rosow-Breslau subscales, and 3 equals disability in all three subscales (see Table 2). The CD1 achieved a coefficient of reproduci- bility of 0.98 and a 0.92 coefficient of scalability, demonstrating the index’s high reliability.

Stroke

Surveillance of incident cases of stroke began in 1949 with the daily monitoring of all ad- missions to the only general hospital in Framingham. If a stroke was suspected, the patient was seen in the hospital by the Framing ham Study neurologist, usually within a few days after admission. By applying uniform cri- teria, the neurologist classified each confirmed stroke by type as either atherothrombotic brain infarction, cerebral embolism, intracerebral hemorrhage, subarachnoid hemorrhage, trans- ient ischemic attack only, or other. Further- more, neurological signs and symptoms noted at the time of each biennial examination were followed by a detailed evaluation in the Framingham Study’s Neurology Clinic. In addi- tion, circumstances surrounding all illnesses and

C.E. 41/8-B

722 ALAN M. JETTE el al.

the death of each subject were investigated by screening all available medical information, in- cluding hospital and physician records and post- mortem data to determine the stroke status and underlying cause of death.

Control variables

To minimize the chance of detecting a spur- ious relationship between the onset of a stroke and subsequent physical disability among those living in the community, we statistically con- trolled for the effect of co-existing congestive heart failure, intermittent claudication, coron- ary heart disease, cardiovascular disease risk factors, and reported health history of other diseases related, to disability.

The coronary heart diseases included in our analysis are angina pectoris (isolated), coronary attack (isolated), coronary attack and angina pectoris combined, and sudden death. A definite diagnosis of congestive heart failure required a minimum of two major (e.g. in- creased heart size and rales) or one major or two minor criteria (e.g. rales, and bilateral ankle edema and night cough). Intermittent claudi- cation was defined as cramping discomfort in the calf clearly provoked by walking but not present on taking the first few steps, with the pain appearing sooner when walking quickly or uphill and being relieved within a few minutes by rest. Detailed descriptions of each cardio- vascular control variable are available else- where [16].

We controlled for the presence of hyper- tension, obesity, and diabetes, and the three cardiovascular risk factors found in previous analysis to be related to physical disability among the Framingham cohort [17].

Systolic and diastolic blood pressure were taken by the examining physician at examina- tion 14/l 5. Participant height was measured at the first examination; weight was measured at each examination. Body mass index at examina- tion 14/15 was calculated as weight at ex- amination 14/l 5 divided by height squared at examination 1. A casual specimen of whole blood was taken at examination l-4, 6, 8-10, and 12-15 and amount of glucose present as well as information on the use of hypoglycemia agents was used as a measure of diabetes.

Several open-ended questions in the FDS solicited information on the participant’s health status over his or her lifetime. A maximum of 11 self-reported health problems were classified into one of the 233 codes. For the present

analyses, 131 codes were grouped into 16 cat- egories of health problems. Eight of the 16 categories were found to be related significantly to physical disability and are included as control variables in these analyses [17].

STATISTICAL METHODS

We chose a logistic model for multivariate analysis similar to that described by McCullagh [18], since the CDI, our dependent variable, is an ordered categorical variable consisting of four levels of increasing severity. In this ap- proach, the probability of being at the ith level or higher is written as a logistic function of the explanatory variables with a constant term de- pending on the value of i. The model used permits inclusion of continuous explanatory variables. Maximum likelihood was used for estimation, and tests were based on the esti- mates divided by their standard errors. Separate ‘sex-specific analyses of the multivariate relation- ship between stroke status and disability were accomplished on computer using the logistic procedure in the statistical analysis system avail- able from the SAS Institute, Inc. In addition to age, each logistic regression controlled for three cardiovascular risk factors: hypertension, body mass index and diabetes; angina pectoris (iso- lated) coronary attack (isolated), combined coronary attack and angina pectoris, intermit- tent claudication and congestive heart failure; and eight general health conditions: arthritis, accidents, allergies, cancer, hernia, neurologic disease (excluding stroke), respiratory disease and back disease.

REmLTs

There were 47 female and 59 male survivors of one or more strokes available for this analy- sis. Table 3 displays the distribution of type of

Table 3. Per cent distribution of type of stroke, through examination 14/15 by sex (Frami@am Study, 1949-1978)

Percent

TYIX of stroke Women Men

Atherothrombotic brain infarction 51 47 Cerebral embolism 11 13 Intracerebral hemorrhage - 2 Subarachnoid hemorrhage 13 Transient ischemic attack only 19 2; Other 4 2 Undetermined

(n =*47, (n =‘59)

724 ALAN M. JETIX et al.

Table 4. Logistic regression of residual disability among community-dwelling Framingham men (Framingham Disability Study, 1976-1978, N = 1036)

Multiple logistic

regression Standard Variable coefficient error z R-Square

Stroke 1.78 0.28 6.1** 0.12 Control variables

Age 0.04 5.3** 0.10 Angina pectoris (isolated) 1.27 0”:: 5.2** 0.10 Coronary attack (isolated) 0.41 0.25 0.01 Coronary attack and angina pectoris 1.72 0.28

;.;** 0.12

Congestive heart failure -0.32 0.45 -0:7 0.00 Intermittent claudication 0.38 0.24 0.01 High blood pressure (14/15) 0.06 0.13

IE 0.00

Diabetes 0.29 0.17 1:6 0.01 Body mass index (14/15) 0.02 0.01

:.;** 0.00

Arthritis 0.83 0.14 Allergies 0.95 0.41 212

0.11 0.03

Cancer 0.60 0.26 2.2 0.03 Neurological problems

(excluding stroke) 1.14 0.33 3.3** 0.06 Respiratory problems 0.45 0.17 2.5** 0.04 Back problems 0.72 0.21 3.4** 0.06 Hernia problems 0.27 0.14 1.9 0.02 Bone iniuries and other accidents 0.32 0.17 1.8 0.02

**p Q 0.01.

Table 5. Logistic regression of residual disability among community-dwelling Framingham women (Framingham Disability Study, 19761978, N = 1504)

Multiple logistic

regression Standard Variable coefficient error z R-Square

Stroke 0.79 0.30 2.5** 0.03 Control variables

Age 0.06 0.00 9.5** 0.15 Angina pectoris (isolated) 1.17 0.19 5.9** 0.09 Coronary attack (isolated) 0.64 0.32 2.0 0.02 Coronary attack and angina pectoris 1.44 0.31 4.5** 0.07 Congestive heart failure 1.17 0.31 3.6** 0.05 Intermittent claudication 0.21 0.26 0.7 0.08 High blood pressure (14/15) 0.34 0.10 3.2** 0.04 Diabetes 0.12 0.17 0.7 Body mass index (14/15) 0.02 0.01 2.4** 0”:: Arthritis 0.65 0.10 6.4** 0.10 Allergies 0.30 0.28 0.00 Cancer 0.57 0.22

:I** 0.03

Neurological problems (excluding stroke) 0.62 0.21 2.8** 0.04

Respiratory problems 0.25 0.18 1.3 0.00 Back problems 0.69 0.16 4.1** 0.06 Hernia nroblems 0.31 0.17 1.8 0.01 Bone i&tries and other accidents 0.50. 0.15 3.2** 0.04

**p Q 0.01.

Our findings are consistent with some other investigations which have examined sex differ- ences in chronic disabling conditions among the aged. In one national sample of older men and women in the U.S., 34.9% of women in contrast to 43.2% of men reported limitation of activities due to chronic conditions [l]. In analyses of unpublished tabulations from the National Health and Nutrition Examination Survey (1971-74), Verbrugge reports that 1.9% of

women 65 years and older compared with 2.9% of men report having had a stroke which limits their activity [l]. Although in most national studies older women report more chronic health problems than older men, the major anomaly is that a larger percentage of older men report they are limited in major activities due to specific chronic conditions such as stroke.

Our analyses suggest that these observed sex differences in reported disability due to stroke

The Framingham Disability Study 123

stroke by sex. Approximately half of the surviv- ing non-institutionalized male and female stroke victims suffered an atherothrombotic brain in- farction. Six women but only three men sur- vived following a subarachnoid hemorrhage. Seventeen of the men (29%) compared with nine women (19O/,) suffered a transient ischemic attack only.

There were no significant male-female differ- ences in stroke history. The average age of first stroke was 64.8 years for women and 63.8 years for men. Average age at the time of the most recent stroke was 65.7 years for women and 64.2 years for men. There were no statisti- ’ tally significant sex differences in number of strokes or in number of years since the most recent stroke (7.5 years for women, 6.8 years for men).

Figure 1 displays the sex-specific per cent distribution of FDS participants according to their score on the CDI. Clearly, more women than men reported disabilities. Seventy-nine percent of the women compared to 60% of the men report some level of physical disability.

Figure 2 displays the age- and sex-specific prevalence of disability for those with and with- out stroke living in the community. Eighty per cent of male survivors of stroke and 90% of the female survivors reported some physical disabil- ity. Of those without a stroke, 59% of the men and 74% of the women reported some degree of physical disability.

Tables 4 and 5 display the sex-specific logistic regression analyses undertaken to ascertain the degree to which physical disability in this cohort could be attributed to a history of stroke after adjusting for the potential impact of age, other

50 WOMEN MEN (n =15c4) ln=10361

40-

P 30-

h 8

20-

10 -

o- 0 1 2 3 0 1 2 3

Fig. I. Per cent distribution of mea and women at examina- tion 14/15 by their more on the cumulative disability index

(Framingham Study, 19761978).

:- -“- I . . . . . . . . _...-“-” . . . ...“..... _g

: _ ./ 80

e_._.-‘-’ -o.M” A tn. 591

,-A , n. 977)

__A----- _*-

_e-- c-

Age Cohort

Fig. 2. Framingham men and women with disability by age and stroke status. *Disability is defined aa a score of 1, 2,

or 3 in the cumulative disability index.

cardiovascular diseases, three cardiovascular risk factors, and eight self-reported health prob- lems. Among surviving men in the community, a history of stroke explains 12% of the total variance in physical disability and is the strongest predictor of physical disability in this model. Some of the control variables (age, angina pectoris (isolated), coronary attack and angina pectoris combined, and a history of arthritis) also explain 10% or more of the variance among men. Among surviving women in the community, a history of stroke is much less important to understanding degree of physical disability, explaining 3%~ of the total variance. Only two of the control varia- bles (age and a history of arthritis) explain 10% or more of the overall variance among women,

DISCUSSION

Although older men and women are known to die from the same major causes, they proba- bly are not disabled by the same conditions. In this investigation of community-dwelling sur- vivors of stroke among the Framingham Study cohort, a history of stroke was the strongest multivariate predictor of physical disability among surviving men in an analysis that con- trolled for age, other cardiovascular diseases, cardiovascular risk factors and other disabling health conditions. SuiTering a stroke, however, was not a strong predictor of physical disability among women, explaining only 3% of the total variance, even though in the overall Framing- ham cohort older women were more disabled than men.

The Framingham Disability Study 725

among these community-dwelling survivors cannot be explained fully by sex differences in the type or history of stroke. There are no observed sex differences among the Framing- ham cohort in number of strokes, years since the onset of the most recent stroke, or age at first stroke. More men than women survivors suffered a transient ischemic attack only, pre- sumably the least disabling type of stroke, while more than twice as many women than men suffered and survived a subarachnoid hemor- rhage. These differences among survivors pat- tern very closely the gender distribution of type of stroke for all who suffered a stroke [2].

The inclusion of transient ischemic attacks in our definition of stroke had little effect on the results. Recalculating age- and sex-specific logis- tic regression analyses excluding those with transient ischemic attacks only produce almost identical results for women. For men the only change is a small decrease in the stroke coeffi- cient for men 6574 years of age.

It is unlikely that these observed sex differ- ences among the non-institutionalized are due to differential cumulative survival rates for men and women. At the end of the 10 years of follow-up, the cumulative survival rate for all strokes in the Framingham cohort was 35%. Survival was better for women than men which continues a trend established within the first few years following a stroke. This superior survival experience in females was not due to age differ- ences since the average age of onset for the two groups is remarkably similar [2]. Sex differences in recurrence of stroke may explain, in part, our results. Recurrence among stroke survivors is common and the rate is slightly higher for men than women. Recurrence in men is strongly influenced by the presence of cardiac comor- bidity prior to the initial stroke [19].

Our multivariate findings in the degree of physical disability in Framingham survivors at- tributable to stroke confirms, in part, previous analyses of the same cohort by Gresham et al., using different statistical methods and different measures of disability [20,21]. By comparing the disability of Framingham survivors of stroke to an equal number of Framingham Study controls matched for age and sex, Gresham’s team re- ports statistically significantly more disability among survivors of stroke. Observed differences between stroke survivors and matched controls were not large, suggesting that once an elder survived a stroke the prognosis for eventual recovery of pre-stroke function was reasonably

good. Although Gresham’s group did not report their disability findings separately by sex, they did note that there was no statistical difference between men and women in the pattern of neurological deficit, eliminating another po- tential explanation for the sex differences we observed.

Gresham’s estimate of the prevalence of dis- ability among survivors of stroke is quite similar to ours even though they included nursing home and chronic hospital residents in their sample, and used very different disability measures. Gresham et al., report that 90% of the 119 Fram- ingham cohort survivors of stroke demonstrated one or more of four disabilities (i.e. dependence in ADL, dependence in mobility, decreased level of vocational function, and decreased socializa- tion outside the home) compared with a preva- lence of 58% in an equal number of matched controls. (Their figures were based on the Don- aldson +ctivities of Daily Living Evaluation Form f

B r observed performance of daily activi-

ties an mobility functions and a questionnaire to assess work and socialization activities.) In our investigation where the CD1 was used to measure self-reported disability, we estimated that 85% of the 111 non-institutionalized Fram- ingham stroke survivors had some level of phys- ical disability compared with 71% of the 2469 cohort members without stroke.

Comparisons drawn between our estimates of disability due to stroke and prospective in- vestigations conducted in other populations suggest a lower level of residual disability among Framingham cohort survivors living in the community, but by definition rates exclude approximately 1.4% of the potential study pop- ulation (i.e. the 41 institutionalized members who did not receive their examination at the clinic who could be stroke survivors also.) The World Health Organization sponsored a 17 center investigation both in developing and: developed countries. At one year post stroke, 38% reported dependence in daily activities [22]. Ahlsio et al., studied longterm disability in all patients from Stockholm who sought care for stroke during 1979. At 2 years post stroke, 24% of the 70 survivors had some disability in basic activities as assessed by the Katz index [23]. In a Finish Investigation, 32% of the 154 survivors of stroke displayed dependence in activities 12 months after onset [24]. Different methods of measuring disability, sample differences and varying time frames post-stroke make it difficult to interpret these cross-national differences.

126 ALAN M. JETIX et al.

Limitations of the study design merit atten- tion. We were unable to limit our analyses to persons with incident physical disability during the duration of the Framingham Study. Assess- ment of physical disability status was not made prior to examination 14/1X It is possible that some people reporting greater levels of physical disability at examination 14/ 15 in fact may have been disabled at the start of their participation in the Framingham Study; their disability may have preceded the onset of stroke.

Because the study group consists of those individuals who survived, stayed out of long- term care institutions, and continued to partici- pate in the investigation, selection effects may play some role in any observed association or lack of association. Those who escaped death and remained in the Framingham Study may differ in many unmeasured ways from those who died or dropped out of this investigation.

Finally, although an attempt was,made to control for various other health prob&ms, the amount of information on the relationship be- tween these problems and disability was limited. One can never be sure that a statistical model including terms for these health problems achieves complete comparability with respect to these health problems.

Acknowledgement-The authors wish to thank Dr Lois Verbrugge for her helpful comments on an earlier version of the manuscript.

1.

2.

3.

4.

5.

6.

REFERENCES

Verbrugge LM: A health profile of older women with comparisons to older men. Res Aging 1984; 6: 291-322. Wolf PA, Dawber TR, Thomas HE ef al. Epidemiol- ogy in stroke. In: Thompson RA, Green SR (Eds). Stroke. New York: Raven Press: 1977. Verbrugge LM. Women and men: mortality and health of older people. In: Riley WW, Hess BB, Bond K (Eds). Aging ln Soeiefy: Selected Reviews of Recent Reaeareb. Hollisdale, N.J.: Erlbaum; 1983. National C-enter for Health Statistics. Advance report of final mortality statistics, 1979. Moatkly Vital Statls- ties Report 1982; 31 Supplement. Havlik RJ, Feinleib M (Eds). Pme Conf on the Decllw lo Coronary Heart Dieeaee Mortality. U.S. Dept HEW; 1979: NIH Publ. No. 79-1610. Williams TF. Comprehensive functional assessment: An overview. J Am Gerht Sot 1983; 31: 636.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

Dawber TR, Meadows GF, Moore FE, Jr. Epidemio- logical approaches to heart disease: The Fra&ngham Studv. Am J PubBe Health 1951: 41: 279-286. Branch LG, Jette AM: The F&&ham Disability Study. I. Social disability among the aging. Am J Pnblic Healtk 1981; 71: 1202-1210. Jette AM, Branch LG: The Framingham Disability Study. II. Physical disability among the aging. Aa J Public Health 1981; 71: 1211-1216. Katz S, Downs TD, Cash HR ef al. Progress in the development of an index of ADL. Cerontoh@t 1970; lo: 20-30. Branch LG, Katz S, Kniepmann K. et al. A prospec- tive study of functional status among community dwelling elders. Am J Pub& He&b 1984: 74: 226- 268. Rosow I, Breslau H. A Guttman health scale for the aged. J Gerontol 1966, 21: 556-559. gagi SZ. An epidemiology of disability among the adults in the United States. Mubank Mem md 0 1976; 54: 439-468. Foley D, Bennan L, Branch L et al. Physical function- ing. in: Huntley J et al. (Eds). EstabBshed Popuiati for EddemloIoeie Studies of the EIderI% U.S. Deut of Healih and H&XII Services, 1987: NIk Publ. No. 86, 2443. Comoni-Huntley JC, Foley DJ, White LB et al. Epi- demiology of disability in the oldest old: Methodologic issues and preliminary findings. Milbank Mem Fund Q 1985; 63: 350-376. Shurtleff D. Some characteristics related to the inci- dence of cardiovascular disease and health: Framing- ham Study, 16-year follow-up. Sect 30. In: Kannel WB. Gordon T (Ed& Tbe Framinabem WV: An ‘Epidemiologicel‘ In&tigation of &rdiovma&r Dieeaee. Washington, D.C.: US DHSW, February 1974 Pinsky JL, Branch LG, Jette AM et al. Framingham Disability Study: Relationship of disability to cardio- vascular risk factors among persons free of diagnosed cardiovascular disease. Am J EpldemIoI 1985; 122: 644656. McCullagh P. Regression models for ordinal data. J R Stat Sot B 1980; 42: 109-142. Sacco RL, Wolf PA, Kannel WB et al. Survival and recurrence following stroke. Stroke 1982; 13:\ 29&295. Gresham GE, Fitzpatrick TE, Wolf PA ef ul. Residual disability in survivors of stroke: The Framingham Study. N Engl J Med 1975; 293: 954-956. Gresham GE, Phillips TF, Wolf PA et al. Epidemio- logic profile of long-term stroke disability: The Fram- ingham Study. Arch Pbys Med Rebabil 1979; 60: 487491. Aho K, Harmsen P, Hatano S et al. Cerebrovascular disease in the community: Results of a WHO collabor- ate study. BuB WHO 1980; 58: 113-130. Ahlsio B, Briton M, Murray V et al. Disablement and quality of life after stroke. Stroke 1984; 1% 886-890. Kotila M, Waltimo 0, Niemi ML er al. The profile of recovery from stroke and factors influencing outcome. Stroke 1984; 15: 1039-1044.