Association between depression and cognitive impairment in aged male war veterans

This study examined the association between both depressive symptoms and depressive disorder and subsequent cognitive performance and incident dementia. Participants were selected randomly from male veterans of World War II living in Sydney, Australia in 1982 (n=342). Those surviving were interviewed again in 1991 (n=209). Depressive disorder and dementia were diagnosed clinically. Depressive symptoms were assessed by a standard self-completed scale. Cognitive performance was assessed by 18 standard neuropsychological tests representing a range of mental functions. There was essentially no predictive and no concurrent association between depressive disorder and cognitive performance. There was a marginal correlation between depressive disorder in 1982 and dementia in 1991 but no concurrent association in 1991. Initially, depressive symptoms appeared to be associated with cognitive impairment, both predictively and concurrently. However when verbal intelligence was controlled, the predictive association disappeared for all but two cognitive performance tests and the concurrent association weakened distinctly across all tests. We concluded that cognitive performance and incident dementia were not predicted by depressive disorder nor by depressive symptoms after adjusting for the effect of intelligence.