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Five-year mortality in relation to dementia and cognitive function in 95-year-olds

From the Neuropsychiatric Epidemiology Unit (A.B.-H., D.G., I.S.), Psychiatry Section, Institute of Neuroscience and Physiology, Sahlgrenska Academy at Göteborg University, Sweden; and Medical College of Wisconsin (D.G.), Milwaukee.

Address correspondence and reprint requests to Dr. Anne Börjesson-Hanson, Neuropsykiatri SU/Mölndal, Wallinsgatan 6, SE-431 41 Mölndal, Sweden anne.borjesson{at}neuro.gu.se

Background: Dementia is a known predictor of mortality, but most studies include small numbers of participants above age 90. The influence of dementia or cognition on mortality in this age group is therefore uncertain.

Objective: To examine 5-year mortality in relation to dementia and cognitive performance at age 95.

Methods: A population sample of 338 individuals examined at age 95 was followed to age 100. Dementia was diagnosed according to DSM–III-R criteria. Cognitive function was measured using the Mini-Mental State Examination (MMSE). Information on severe physical disorders was obtained from the Swedish Hospital Discharge Register, and date of death from the Swedish Population Register.

Results: Five-year mortality was higher in 95-year-olds with dementia than in 95-year-olds without dementia (96% vs 73%; p < 0.0001), even when adjusting for severe physical disorders. A Cox regression analysis with calculation of population attributable risk (PAR), calculated from adjusted relative risks, showed that mortality was predicted by dementia (PAR 42%), cardiac disease (PAR 17%), cancer (PAR 6%), and male sex (PAR 7%), but not by stroke. Among the subjects without dementia, cognitive performance measured using the MMSE (n = 133 with complete tests; 81% of the subjects without dementia) predicted mortality. For each point increase in the MMSE, mortality decreased by 13%.

Conclusions: In 95-year-olds, dementia, as well as cognitive performance in the subjects without dementia, influences mortality. When controlling for other severe medical conditions we found dementia to be the leading cause of deaths among the oldest old. The reason why dementia and cognitive function predict life expectancy requires further elucidation.

Abbreviations: AD = Alzheimer disease; ADL = activities of daily living; AF = atrial fibrillation; AP = angina pectoris; CHF = congestive heart failure; COPD = chronic obstructive pulmonary disease; CPRS = Comprehensive Psychopathological Rating Scale; DSM-III-R = Diagnostic and Statistical Manual of Mental Disorders, third edition, revised; MI = myocardial infarction; MMSE = Mini-Mental State Examination; PAR = population attributable risk; RR = relative risks; VaD = vascular dementia.

Supported by grants from The Swedish Research Council (no. 11267), Swedish Council for Working Life and Social Research (no. 2849, 2835, and 0762), Alzheimer Association USA (no. IIRG-03-6168), Hjalmar Svensson Foundation, and National Institutes of Health/National Institutes on Aging 1R03AG026098-01A1.

Disclosure: The authors report no conflicts of interest.

Received March 12, 2007. Accepted in final form June 5, 2007.