(Stroke. 2000;31:2354.)
© 2000 American Heart Association, Inc.
Original Contributions |
From the Departments of Public Health (S.-L.W., S.-P.C.) and Family Medicine (M.-C.L.), Chung Shan Dental and Medical College, and National Institute of Family Planning, Department of Health, Executive Yuan (M.-C.C.), Taichung, Taiwan; and the Division of Epidemiology and Public Health, Institute of Biomedical Sciences, Academia Sinica, and School of Public Health, National Taiwan University (W.-H.P.), Taipei, Taiwan, ROC.
Correspondence and reprint requests to Shu-Li Wang, Division of Evironmental Health and Occupational Medicine, National Health Research Institutes (NHRI), No. 100, Shih-Chuan 1st Road, Kaohsiung 807, Taiwan ROC. E-mail wang21{at}nhri.org.tw
| Abstract |
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MethodsA total of 99 stroke survivors, from a
representative national sample of elders aged
65
years on December 31, 1988, whose strokes occurred in the period
19891993, were followed for mortality until July 1, 1995. Personal
data were gathered through home interviews conducted by well-trained
community nurses, and mortality data were obtained from the national
census office by using identification card numbers. Cox proportional
hazards regression analysis and the stepwise technique were
used to search for important prognostic factors of survival.
ResultsWomen experienced a higher mortality rate (139.8 per 1000 person-years) than men (126.4 per 1000 person-years), as age-adjusted for World Health Organization world-population figures. Stroke patients who received continuous treatment for diabetes experienced mortality risks similar to those of patients without diabetes and much lower risks than those with discontinuous diabetes treatment. Cognitive impairment was also an independent predictor of survival (relative risk 2.69, P<0.05). In addition, patients with both cognitive and mobility impairments had a 2- to 3-fold greater risk of mortality than those with only a single abnormality.
ConclusionsThis first report on the various prognostic factors related to survival of elderly stroke patients in Taiwans Chinese population emphasized the benefit of continuous diabetes treatment in improving survival chances. These stroke patients should also be monitored for cognitive and mobility impairments and undergo rehabilitation.
Key Words: elderly epidemiology stroke outcome survival
| Introduction |
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65 years.2 Stroke is also related to other
major chronic diseases and disabilities in the elderly.3 4
Investigation into stroke in the elderly is especially important
because the Taiwanese population is aging rapidly. Some 8.2% of
Taiwans population is now
65 years of age, and it is estimated that
the figure will increase to 18.4% by the year 2030.
The prevalence of stroke in Taiwan was 33.7 to 42.5 per 1000 persons
aged
65 years in the 1986 survey.5 This is similar to
prevalence rates in other developed countries. The incidence of stroke
in Taiwan is also similar to rates in other developed
countries.6 7 However, survival rates among stroke
patients in Taiwan were lower than those in the United States and
similar to those in Japan.8 Data from a nationwide
registry of cases of acute stroke from 26 study centers in Taiwan
during the period 19881991 showed a 1-year survival rate of 74.3%
and a 2-year rate of 67.7%.9 However, no prognostic
factors were examined in these previous studies to determine survival
chances except types of stroke. Available data about the relationship
between stroke predictors and survival were derived mainly from stroke
registries based on clinical findings in acute cases, in which type of
stroke was found to be an independent and significant predictor of
survival.10 11 12 Because none of these studies were
targeted to the elderly, disabilities such as cognitive impairment or
depression were not investigated. In addition, modifiable factors
related to survival were also proposed. A community-based study of the
elderly, which used self-reporting to identify stroke cases, showed
increased blood glucose, cognitive impairment, and other subclinical
diseases to be important predictors of survival.13
Nonetheless, to the best of our knowledge, no such data on survival
predictors are available for Chinese populations. The aim of the
present study was to examine prognostic factors of survival for
elders suffering strokes, with specific focus on depression and
cognitive and physical impairments, by using data from a nationally
based cohort of individuals aged
65 years in Taiwan.
| Subjects and Methods |
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60 years
as of December 31, 1988, were selected by systematic random sampling
from each selected lin. Respondents names and addresses were obtained
from local population census offices. Selected respondents who no
longer resided at the addresses listed for them within selected lins
were interviewed at their new addresses, wherever in Taiwan they
happened to be. As shown in Figure 1
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Data Collection and Various Scales
Baseline data collected in 1989 and follow-up data collected in
1993 were derived from home interviews by well-trained community
nurses. Subjects were asked: "Do you have any of the following
illnesses, diseases, or symptoms at the present time?" The
disease list included stroke. Prognostic factors recorded in 1993
that served as predictors of survival status in 1995 included
demographic data, disease and treatment histories, lifestyle, and
economic status. The various scales used in the present study
included physical functions, cognitive impairment, and depression. The
Barthel Index15 and Karnofsky scale16 were
used to assess physical functions, including activities of daily living
(ADL), instrumental activities of daily living (IADL), and mobility
impairment. Details of each scale are listed in the Appendix.
Disabilities in ADL, IADL, and mobility impairment were defined as
being completely incapacitated in 1 or more listed items. Assessment of
cognitive impairment17 was based on the number of
questions answered incorrectly. Depression18 was defined
as the number of negative feeling lasting for 5 to 7 days, on average,
every week. Two questions designed to elicit positive feelings were
coded in opposite ways during analysis. Thus, the total number
of expressed negative feelings revealed the degree of depression.
Follow-Up
A total of 99 subjects who sustained strokes in the period
19891993 were tracked for survival until July 31, 1995. To guarantee
successful follow-up, telephone interviews were conducted in 1991.
Life/death status data and death certificates were obtained from the
local population census offices, and dates of death were recorded
for survival analyses. A 99% follow-up rate was achieved, with
only 1 subject lost to follow-up.
Statistical Methods
A direct method of age standardization was used for various
mortality rates in stroke patients that included all people aged
65
in Taiwan and truncated (
65) WHO world population as reference
populations. An indirect method of age standardization was used to
calculate the standardized mortality ratio (SMR) in order to
compare the mortality rates in our subject constituency with those of
the general population aged
65 years in Taiwan.19
Assessment scores for the various scales were first grouped into 3
categoriesnormal, mild, and severeto facilitate statistical
analyses and presentation. For ADL and mobility
impairment, 1 to 3 items of disability were combined as "mild"
impairment, and 4 to 6 items were grouped into the "severe"
category. Zero items were considered "normal." Similar grouping was
applied to IADL (0, 14, and 58), cognitive impairment (0, 15, and
610), and depression (0, 15, and 611). Survival curves showed
markedly lower survival rates for subjects with severe disabilities
compared with the other 2 groups. Thus, in regression analyses,
disability was treated as a dichotomous variable, with the normal
and mild categories as value 0 and the severe category as value 1.
Kaplan-Meier survival curves were drawn for the various groups. A Cox proportional hazard regression analysis was used to estimate relative risks for univariate and multivariate analyses. In multivariate analysis, a stepwise technique was used to model survival.
| Results |
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Focusing on the 99 patients suffering stroke, Table 1
shows all-cause mortality rates for
stroke patients between 1993 and 1995. Among men, the rate was higher
in the
75 years age group than in the 65 to 74 years age group.
However, among women the rate was higher in the 65 to 74 years age
group. The overall age-adjusted mortality rate was 120.48 per 1000
person-years using Taiwans population as a reference, and 121.25
using the WHO world population as a reference. Thus, the women we
studied appeared to experience higher mortality rates than men, but the
differences were not statistically significant. Stroke patients had a
5.37-fold greater risk of dying than the general population of Taiwan
aged
65 years.
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Table 2
shows the distribution of
characteristics among the 23 deceased patients compared with those
among the 75 survivors. We found that discontinuous diabetes treatment
signified a relative risk (RR) as high as 9.78 (P=0<0.001)
compared with absence of diabetes or continuously treated diabetes.
Each of the functional scales, except those for depression and IADL, is
associated with a significantly increased risk of death. Patients who
answered 6 to 10 items incorrectly during cognitive impairment testing
experienced a 4.18-fold (P=0.002) greater risk of death compared with
those who gave 0 to 5 incorrect answers. Being bedridden showed
borderline significance in predicting death, with an RR of 2.65
(P=0.055). Accordingly, we investigated these prognostic
factors further by regression analyses. We found that lower-income
patients had an RR of 2.26, but these findings were not statistically
significant.
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We also calculated age-adjusted mortality rates according to diabetes and cognitive impairment. Patients with diabetes were divided into those who received and did not receive treatment. We found that stroke patients who received continuous treatment for diabetes (135.0 per 1000 person-years) experienced mortality risks similar to those of patients without diabetes (92.5) and much lower risks than those of patients with untreated diabetes (1601.2). Age-adjusted mortality rates increased consistently and roughly linearly with increasing grading on the cognitive impairment scale: 0, 71.1, 153.2, to 224.7 per 1000 person-years for those with 0, 1 to 3, 4 to 6, and 7 to 10 items of cognitive impairment, respectively.
Survival Analysis Outcome
Figure 2
shows that survival rates
were consistently lower for stroke patients than for those who
had not sustained strokes. The second-year survival rates are shown
according to the occurrence of stroke by sex. Women had slightly
higher survival rates than men when neither had sustained strokes. When
both had suffered strokes, women consistently experienced lower
survival rates than men, reaching a difference of 9.7% in survival
rates by the second year of follow-up.
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As shown in Figure 3
, subjects who had
serious mobility impairment had lower survival rates than those with
less-severe mobility impairment. Survival curves showed markedly lower
survival rates in subjects with 4 to 6 items of mobility impairment
compared with the other 2 groups. This association illustrates a
typical survival curve pattern for the various scales with the
exception of depression, for which the association was less clear.
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Table 3
, generated by Cox stepwise
regression analysis, shows that discontinuous diabetes
treatment and cognitive impairment are significant predictors of
survival when adjusted for age (discontinuous diabetes treatment: RR
9.56, P<0.01; cognitive impairment: RR 2.69,
P<0.05). Mobility impairment was also found to be a
noteworthy predictor, with an RR of 1.71 when included in the model
(data not shown), but it did not achieve statistical significance
(P=0.35). Because cognitive and mobility impairments are
correlated, further analysis of the 2 predictors showed an
additive effect on survival.
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Mobility impairment was a significant predictor of survival in univariate analysis, with an RR of 4.01, but became insignificant in multivariate analysis. We did further analyses and found that the mortality risk was as high as 346.2 person-years in subjects with both serious cognitive and mobility impairments compared with those having only serious cognitive impairment (117.59) or only mobility impairment (156.16). Those without serious cognitive or mobility impairments had the lowest rate, 41.4 per 1000 person-years.
| Discussion |
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Stroke patients with continuous diabetes treatment experienced mortality risks similar to those without diabetes, and much lower risks than those with discontinuous diabetes treatment. Discontinuous diabetes treatment was also found to have the highest RR for mortality at 9.56 (P<0.01), independent of age and cognitive impairment. Studies of stroke-survival prognoses among white Americans20 and Canadians11 showed diabetes to be a significant predictor of mortality independent of heart diseases. Similarly, analysis of stroke registry data in Sweden10 showed that the presence of diabetes was a significant predictor of both mortality and recurrence in stroke patients during the period 19891992. However, whether subjects had continuous treatment for diabetes was not considered in these 3 studies. Our results emphasize the benefit of continuous diabetes treatment in improving survival chances among stroke elderly. We further investigated these deceased stroke patients without continuous diabetes treatment through review of their death certificates and medical records and discussions with their clinicians. Diabetes was even not mentioned on their death certificates. Reviews of the medical records showed that blood glucose level was not measured or monitored in 1 patient. Diabetes was not under control in 2 patients because the cost was relatively high during that time, when the national health insurance was not available. The other contributory reasons may result from the lack of awareness of blood glucose control in these patients (personal communications with the subjects clinical doctors). It is pointed out that better surveillance of diabetes followed by proper treatment would be crucial to decrease mortality, particularly in women, from our survival observations.
Cognitive impairment was also found to be an important and
independently significant predictor of survival, with an RR of 4.18
(P<0.01) in univariate analysis and
2.69 (P<0.05) in multivariate
analysis, when adjusted for age and discontinuous diabetes
treatment. Mortality rates also increased consistently with
severity of the impairment. Similar results21 were
reported for clinic-based ischemic stroke patients aged
60
years, in which dementia was the most significant predictor of 4.5-year
survival, with an RR of 3.11 (95% CI 1.79 to 5.41). Cognitive
impairment, as assessed by the 10 questions used in the present
study, showed a high degree of predictive accuracy in determining
severity of impairment. We recommend using this simplified mental
status test, which can be widely applied, in community settings.
Cognitive impairment is generally considered a non-modifiable factor.
However, it has been suggested that intervention in high blood pressure
may prevent dementia in elderly men.22 In addition, a
3-year follow-up study23 of a population-based stroke
registry in New Zealand showed that patients who lost consciousness had
the lowest survival rates, especially when the strokes occurred in
institutions. Though cognitive impairment, like other scales, is an
appropriate measurement of stroke severity, its value in predicting
survival helps clinicians and health planners assess needs.
Mobility impairment was also found to be an important predictor of survival, with an RR of 4.01(P=0.002) in univariate analysis. In multivariate analysis it became insignificant. Further analysis demonstrated an additive effect with cognitive impairment. Mortality totaled 346.22 per 1000 person-years in those with both severe mobility and cognitive impairments. A population-based cohort study of the elderly24 showed that physical functioning, as assessed by ADL, together with cognitive impairment predicted the outcomes of strokes. Previous findings for a Chinese population showed that physical functions were related to the prevalence of depression in stroke survivors,25 which may imply that improvements in physical functioning may also reduce the severity of depression.
Regarding sex differences, stroke-free women had slightly higher survival rates than men. However, among stroke patients, we found that women experienced lower survival rates than men, with a difference of 9.7% by the second year of follow-up. Because observation showed that the distribution of stroke type between sexes in Taiwan7 was very similar, the reason for this survival difference between the sexes maybe result from the difference in risk-factor distribution. It is found that women (5.6%) had a higher rate of discontinuous diabetes treatment than men (3.2%), and this may be the reason for their higher mortality rates. In addition, we found that female stroke patients tend to have slightly more items of ADL and/or morbility impairment than male stroke patients (data not shown).
Disease information obtained from self-reports may underestimate the prevalence of disease, particularly in those without apparent clinical symptoms. However, stroke patients usually have acute symptoms and need team care from neurologists, physiotherapists, and nutritionists, and others. Thus, it is unlikely that stroke patients remain unaware of disease very long. A previous study26 showed a sensitivity of 95% and a specificity of 96% for the single question, "Have you ever had a stroke?" Stroke types without apparent symptoms, such as transient strokes and so-called silent strokes or minor strokes, were not considered in the present study.
In summary, the present study demonstrated that the nationally representative elderly study group with self-reported strokes experienced a 5.37-fold greater risk of mortality than the general population. Among elderly stroke victims, women experienced lower survival rates than men. This study even pointed out the importance of better surveillance of diabetes followed by proper treatment to decrease the mortality, particularly in women. Cognitive impairment was also found to be an important and independently significant predictor for survival, and mobility impairment was found to have an additive effect on cognitive impairment. Future work will be directed toward evaluating intervention in these associated factors to improve survival. This may include vigorous diabetes monitoring and treatment, rehabilitation to increase physical functioning, and high-blood-pressure control to reduce the risk of cognitive impairment.
| Acknowledgments |
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| Appendix 1 |
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1. Bathe yourself?
2. Dress and undress yourself?
3. Feed yourself?
4. Stand up and sit down without assistance?
5. Walk around your home?
6. Use the toilet by yourself?
IADL
Are you able to:
1. Shop for personal items such as toiletries and medicines?
2. Manage your money, for example, keep track of expenses, and pay bills?
3. Climb 2 to 3 flights of stairs?
4. Take buses or trains by yourself?
5. Walk about 200 to 300 meters?
6. Do heavy housekeeping chores, such as scrubbing floors, cleaning storm ditches, moving furniture, and washing windows?
7. Do light housekeeping, such as mopping floors, washing dishes and disposing of garbage?
8. Use the telephone?
Mobility Impairment
Are you able to:
1. Stand up without assistance and stand continuously for about 15 minutes?
2. Crouch?
3. Reach up over your head?
4. Use your fingers to grasp and manipulate objects?
5. Lift or carry something as heavy as 11 to 12 kg (25 pounds) of rice?
6. Run 20 to 30 meters?
Cognitive Impairment
Do you know:
1. What your address is?
2. Where you are?
3. The date (day, month, year)?
4. What day it is (day of the week)?
5. Your mothers maiden name?
6. Who is President now?
7. Who was President previously?
8. How old you are?
9. When you were born (day, month, year)?
10. If you have 20 oranges and eat 3, how many will be left? If you eat 3 more, how many will then be left? (Asked four times in succession: 20 to 3=? 3=? 3=? 3=?)
Depression
Most or all of the time (5 to 7 days during the week):
1. I did not feel like eating; my appetite was poor.
2. I felt that everything I did was an effort.
3. I slept poorly.
4. I felt very happy.
5. I enjoyed life.
6. I could not "get going."
7. I felt that people dislike me.
8. I felt depressed.
9. I felt lonely.
10. People were unfriendly to me.
11. I felt sad.
Received May 18, 2000; revision received July 5, 2000; accepted July 5, 2000.
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