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Short Report Abstract Using the 1991 Canadian life table and estimates of the prevalence of
dementia from the Canadian Study of Health and Aging, we have partitioned
the expectation of life at age 65 into years spent in the community and
in institutions, with and without different forms of dementia. The total
expectation of life for women was 26% greater than that for men, but women's
expectations of life with dementia and of life in institutions were more
than twice the corresponding expectations for men. The difference between
sexes was greater for Alzheimer's disease than for vascular and other
types of dementia. Introduction At older ages, dementia is an important cause of disability, institutional admission and death. The burden of dementia falls more heavily on women because they live longer. There are also differences between sexes in the incidence of the main types of dementia and in the likelihood of being institutionalized. In this paper, we quantify these differences in terms of the expected years lived after age 65 with and without dementia, in the community and in institutions. Methods We used data on people aged 65 and over in the 1991/92 Canadian Study of Health and Aging (CSHA).1 The study included 9008 people living in the community and 1255 people in institutions. Those living in the community were first screened for the likely presence of dementia using the Modified Mini-Mental State (3MS) Examination.2 All residents in institutions plus those in the community scoring less than 78 on the 3MS Examination, were offered a clinical examination that classified them into one of four categories: normal, Alzheimer's disease, vascular dementia or other dementia. The CSHA estimated the prevalence, in Canada, of the three categories of dementia by sex and age, both in the community and in institutions. We used these estimates to partition the years of life lived after age 65 derived from the 1991 Canadian life table, using the method described by Sullivan.3 Results Table 1 shows that the total expectation of life at age 65 is 19.98 years for women and 15.80 years for men. This difference of 4.18 years includes 1.22 more years with dementia for women and 1.35 more years in an institution. For every additional year women live in the community without dementia, they spend an extra 1.7 months in the community with dementia and 4.7 months in an institution with dementia. Table 1 also shows the sex ratios (female-to-male ratios) of the various components of the expectation of life. In relative terms, the increased burden for women is greatest for time spent in an institution with Alzheimer's disease. The ratio is lower for vascular dementia, though, in absolute terms, women spend slightly longer with vascular dementia than men, especially in institutions.
Comment Perenboom et al.4 estimated life expectancy at age 65 in the Netherlands, with and without dementia, subdivided by type of residence but not by type of dementia. The results were similar to ours, except that the expected years lived with dementia in institutions were lower. Some of this discrepancy may be due to the definition of an institution or to the methods of estimating the prevalence of dementia in institutions. The following calculations provide a measure of the public health impact of these sex differences. At present, about 225,000 Canadians reach the age of 65 each year. With the current sex differences, this cohort would experience 3,633,000 person-years without dementia and 417,000 person-years with dementia, including 227,000 person-years institutionalized with dementia. If men had the same expectations as women, the expected person-years without dementia for the cohort would increase by 9%, but the expected person-years with dementia would increase by 31%, and the expected person-years institutionalized with dementia would increase by 41%. The difference between sexes in expectation of life at age 65 is primarily attributable to mortality from ischemic heart disease, lung cancer and chronic obstructive lung disease,5 all diseases related to smoking. The apparent advantage of women's longer life expectancy is substantially reduced by the proportion of that time spent with dementia and in institutions. The difference will likely be further shortened by the equalization of the prevalence of smoking in men and women. Acknowledgments The Canadian Study of Health and Aging is funded by the Seniors' Independence Research Program of Health Canada, with funds administered by the National Health Research and Development Program (project 6606-3954-MC[S]). References 1. Canadian Study of Health and Aging Working Group. Canadian Study of Health and Aging: study methods and prevalence of dementia. Can Med Assoc J 1994;150:899-913. 2. Teng EL, Chui HC. The Modified Mini-Mental State (3MS) Examination. J Clin Psychiatry 1987;48:314-8. 3. Sullivan DF. A single index of mortality and morbidity. HSMHA Health Reports 1971;86:347-54. 4. Perenboom RJM, Van de Water HPA, Boshuizen HC. Dementia-free life expectancy in the Netherlands 1993. Paper presented at the 8th Meeting of the Network on Health Expectancy (REVES); 1995 Oct 5-7; Chicago, USA. 5. Wilkins K, Morris S, Lane R. Mortality and morbidity of Canada's seniors: a historical perspective. Chronic Dis Can 1988;9(5):79-84. Author References |
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Last Updated: 1998-10-20 |  |
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