Cognitive impairment and mortality in a cohort of elderly people

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Abstract
Objectives: To investigate the relation between cognitive function and cause specific mortality in people aged 65 and over. Design: A 20 year follow up study of a cohort of randomly selected elderly people living in the community who in 1973-4 had taken part in a nutritional survey funded by the Department of Health and Social Security. Setting: Eight areas in Britain (five in England, two in Scotland, and one in Wales). Subjects: 921 men and women whose cognitive function was assessed by a geriatrician in 1973-4 and for whom data on health, socioeconomic circumstances, and diet had been recorded. Results: Cognitive impairment was associated with increased mortality, in particular death from ischaemic stroke. Those who scored 7 or less on the Hodkinson mental test had a relative risk of dying from stroke of 2.8 (95% confidence interval 1.4 to 5.5), compared with those who gained the maximum score (10), after adjustment for age, sex, blood pressure, serum cholesterol concentration, and vitamin C intake. These associations were independent of illness or social class. At the time of the nutritional survey, cognitive function was poorest in those with the lowest vitamin C status, whether measured by dietary intake or plasma ascorbic acid concentration. The relation between vitamin C status and cognitive function was independent of age, illness, social class, or other dietary variables. Conclusion: The relation between cognitive function and risk of death from stroke suggests that cerebrovascular disease is an important cause of declining cognitive function. Vitamin C status may be a determinant of cognitive function in elderly people through its effect on atherogenesis. A high vitamin C intake may protect against both cognitive impairment and cerebrovascular disease. Key messages In this prospective study of 921 elderly people cognitive impairment was a strong predictor of death from ischaemic stroke Low vitamin C intake and low plasma ascorbate concentrations were also important risk factors for death from stroke Cognitive performance was poorest in people with the lowest vitamin C status A high vitamin C intake may protect against both cognitive impairment and cerebrovascular disease