Exercise, diet, and cognition in a 4-year randomized controlled trial: Dose-Responses to Exercise Training (DR's EXTRA)

Background Evidence for the effects of exercise and dietary interventions on cognition from long-term randomized controlled trials (RCTs) in large general populations remains insufficient. Objective The objective of our study was to investigate the independent and combined effects of resistance and aerobic exercise and dietary interventions on cognition in a population sample of middle-aged and older individuals. Methods We conducted a 4-y RCT in 1401 men and women aged 57-78 y at baseline. The participants were randomly assigned to the resistance exercise, aerobic exercise, diet, combined resistance exercise and diet, combined aerobic exercise and diet, or control group. Exercise goals were at least moderate-intensity resistance exercise ≥2 times/wk and at least moderate-intensity aerobic exercise ≥5 times/wk. Dietary goals were ≥400 g/d of vegetables, fruit, and berries; ≥2 servings of fish/wk; ≥14 g fiber/1000 kcal; and ≤10% of energy of daily energy intake from SFAs. The primary outcome was the change in global cognition measured by the total score of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) neuropsychological tests [CERAD total score (CERAD-TS)]. The data were analyzed using the intention-to-treat principle and linear mixed-effects models. Results There was a trend toward improved CERAD-TS over 4 y in the combined aerobic exercise and diet group compared with the control group (net increase: 1.4 points; 95% CI: 0.1, 2.7; P = 0.06) adjusted for age, sex, years of education, symptoms of depression, and waist circumference at baseline. No other differences in CERAD-TS changes were found across the 6 study groups. Diet did not potentiate the effect of aerobic or resistance exercise on CERAD-TS. Conclusions A combination of at least moderate-intensity aerobic exercise and a healthy diet may improve cognition in older individuals over 4 y, but there was no effect of either of these interventions alone, resistance training alone, or resistance exercise with a healthy diet on cognition.