Original articlesMortality from Dementia in Advanced Age: A 5-Year Follow-Up Study of Incident Dementia Cases
Introduction
Among the age-related chronic disorders, dementia is a highly prevalent condition [1] which causes progressive and severe disability [2]. In a previous study, we found that dementia was the major determinant for the development of functional dependence over three years, whereas other chronic conditions led more frequently to death [3]. Nevertheless, demential has been also reported to shorten survival 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17.
Few data are present in the literature concerning mortality rates specific for dementia in the community 18, 19. Death certificates are generally considered to grossly underreport dementia, even when underlying causes of death are taken into account [20]. In 1986, Chandra and coworkers [18] reported a mortality rate of 0.98 per 1,000 person-years in 85+ old subjects, which is similar to the rate of 1.1 per 1,000 person-years in 80+ old people reported more recently by the Centers for Disease Control in Atlanta [19].
Several community-based studies have investigated mortality in dementia 5, 6, 8, 9, 10, 11, 12, 13, 15, 16, 17, and all showed an increased risk of death in demented compared to non-demented subjects. However, most of these studies have used prevalent rather than incident cases. The few studies that have investigated the risk of dying in incident dementia cases 9, 15, 21, 22 have focused on pre-senile dementia 21, 22, have studied selected populations of elderly [15], or have included patients who came to medical attention. In this last group, very mild cases as well as rapidly progressiving forms of the disease might have been under-represented [9]. The reported relative risk of dying varied between 1.9 to 3.0 for dementia 9, 10, 11, 16 and 1.4 to 2.9 for Alzheimer's disease 8, 12, 13, 15, 17. Additionally, some other authors have suggested that dementia may not necessarily cause decreased life-expectancy in very old age [23].
We had the opportunity to evaluate the impact of dementia on mortality using incident dementia cases from a community-based population followed for 5 years after diagnosis. Information on important covariates such as education and co-morbidity were also available, as was the diagnosis of different dementia types.
Section snippets
Study Population
The study population consisted of a cohort of subjects aged 75 years or older who were not demented at the beginning of the follow-up. The cohort was identified within the Kungsholmen Project's population by means of a cross-sectional study that led to the detection of the prevalent dementia cases [24]. All the inhabitants of an area in Stockholm (Kungsholmen) on October 1, 1987, born in 1912 or before, living at home or in institutions were included in the study population. The incident
Results
The cohort of 989 subjects included 77% women, and 43% highly education subjects. The average age ± SD was 84.3 ± 4.3 years, the mean MMSE score ± SD was 25.2 ± 5.3 points. Thirty-eight percent had a history of at least one of the following conditions, either cancer, heart disease, hip fracture, or stroke without dementia. Those affected by only one of these conditions amounted to 30%, and those affected by more than one condition to 8%. One hundred ninety-nine (20%) subjects developed dementia
Comment
This is one of the few population-based studies where mortality specific for dementia has been investigated by following incident dementia cases identified from a community of elderly subjects, and also where the mortality rate ratio associated with dementia has been estimated after controlling for other chronic medical conditions potentially related to death. The main findings from the present study can be summarized in two points:
- 1.
The impact of dementia on mortality is extraordinarily high,
Acknowledgements
We thank all members of the Kungsholmen Project Study group for their collaboration. We also thank The Swedish Council for Social Research, The Swedish Medical Research Council, The Swedish Society for Medical Research, and the Greta Lindenau-Hansells Foundation.
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