The importance of impaired physical health and age in normal cognitive aging.

The objective of this study was to investigate the importance of impaired physical health and age in normal cognitive aging. In our cross-sectional, clinical and explorative study, medical and neuropsychological data from 118 voluntary healthy controls aged 26-91 years were collected from five recruitment occasions. Health was assessed according to a criterion reflecting clinical and subclinical severity. The examinations included a clinical investigation, brain neuroimaging, and a comprehensive neuropsychological assessment. Regression analyses showed a significant incidence of clinical and subclinical medical disorders that explained 10.8% of the variation in cognitive performance, while age-related impairment explained 5.6%. Findings of the central nervous system were important but various other medical findings explained about half of the health-related variation. Cognitively demanding tasks were more susceptible to impaired physical health while tasks comprising salient motor- and visual spatial elements were more prone to be impaired by age. Our findings suggest (1) that impaired physical health is more important than chronological age in accounting for cognitive impairment across the adult lifespan, (2) that age and health dissociate with regard to cognitive functions affected, and (3) that selection for so-called "super healthy" elderly people might be justified in cognitive research. Because the prevalent diseases in normal aging are potentially preventable, the present findings promise good prospect for prevention of future cognitive disability among elderly people.