Depression and Cognitive Dysfunction in Older U.S. Military Veterans: Moderating Effects of BDNF Val66Met Polymorphism and Physical Exercise

Abstract Objectives Depression is associated with increased risk for cognitive dysfunction, yet little is known about genetic and behavioral factors that may moderate this association. Using data from a nationally representative sample of older U.S. military veterans, we examined the direct and interactive effects of depression, brain-derived neurotropic factor (BDNF) Val66Met genotype, and physical exercise on cognitive functioning. Methods 1,386 older European-American U.S. military veterans (mean age=63) completed a web-based survey and cognitive assessment. Analyses of covariance evaluated the effects of depression, BDNF Met allele carrier status, and physical exercise on these measures. Results Depressed veterans scored worse than non-depressed veterans on subjective measures of cognitive functioning (Cohen d's=0.34-0.57) and objective measures of visual learning (d=0.39) and working memory (d=0.28). Among depressed veterans, those who were Met allele carriers scored worse than Val/Val homozygotes on subjective cognitive measures (d's=0.52-0.97) and an objective measure of visual learning (d=0.36). Engagement in physical exercise moderated the association between depression and cognitive function, with depressed exercisers scoring better than depressed non-exercisers on a subjective measure of reasoning, and objective measures of processing speed, attention, and visual learning (d=0.58-0.99): further, in depressed Met allele carriers, exercisers scored better than non-exercisers on subjective cognitive (d's=0.80-1.92), and objective measures of visual learning (d=0.1.31) and working memory (d=0.67). Conclusions Depression is associated with moderate decrements in cognitive functioning in older U.S. military veterans, and this association is moderated by BDNF Val66Met genotype and physical exercise. Prevention and treatment efforts designed to promote physical exercise may help preserve cognitive functioning in at-risk veterans.