Cognitive functioning and health as determinants of mortality in an older population.

The authors studied whether the ability of cognitive functioning to predict mortality is pervasive or specific, and they considered the role of health in the cognition-mortality association. Data were taken from a sample of 2,380 persons aged 55-85 years who took part in the Netherlands' Longitudinal Aging Study Amsterdam in 1992-1993. Five cognitive measures were distinguished: general cognitive functioning, information processing speed, fluid intelligence, learning, and proportion retained. Mortality data were obtained during an average follow-up period of 1,215 days. Cox proportional hazards regression models revealed that all cognitive functions predicted mortality independent of age, sex, education, and depressive symptoms. When health (self-rated health, medication use, physical performance, functional limitations, lung function, specific chronic diseases) was also taken into account, information processing speed, fluid intelligence, and proportion retained remained independent predictors of mortality, whereas the ability of general cognitive functioning and learning to determine mortality was lost. The authors concluded that the ability of cognitive functioning to predict mortality is pervasive to all cognitive functions that were included in the study when age, sex, education, and depressive symptoms are considered and is more specific to some functions when also controlling for health.