Exercise, fitness and cognition – A randomised controlled trial in older individuals: The DR's EXTRA study

Background Observational studies suggest that higher levels of physical activity and cardiorespiratory fitness associate with improved cognition. However, evidence from randomised controlled trials (RCT) is limited. We hypothesised that increased regular exercise improves cognition in older individuals. The trial is registered: ISRCTN45977199 (http://isrctn.org). Methods A population sample of 1335 men and women aged 57–78 years was randomised into aerobic exercise, resistance exercise, diet, combined aerobic exercise and diet, combined resistance exercise and diet or reference group for a 4-year intervention. Here, we report 2-year interim data. Exercise was assessed by a questionnaire and by maximal oxygen uptake (VO 2max ), an objective measure of exercise, and cognition using Consortium to establish a registry for Alzheimer's disease (CERAD) neuropsychological tests. Findings In the intention to treat analyses, regular exercise increased in exercise groups, but remained unchanged in reference and diet only groups ( P 2max remained unchanged in exercise groups, but decreased in reference and diet only groups ( P 2max to cognition during the first 2 years of intervention. In secondary analyses, improved VO 2max was associated with improved immediate memory in aerobic (β=0.11, P =0.001), resistance (β=0.08, P =0.018), diet (β=0.09, P =0.029) and combined aerobic and diet groups (β=0.09, P =0.013), with improved delayed memory in diet group (β=0.08, P =0.015) and with verbal performance in aerobic group (β=0.14, P =0.044). Those who were in the upper gender-specific VO 2max tertile had a 66.0% (95% confidence interval [CI] 34.2–82.4%, P =0.001) lower, and those in the middle tertile a 56.4% (95% CI 22.6–75.4%, P =0.005) lower risk of developing impaired delayed memory compared to those in the lower VO 2max tertile, after adjusting for potential confounders. Conclusions Present data from a large RCT among older individuals failed to show between group differences on the effects of regular exercise on cognition. However, secondary analyses suggest that higher levels of fitness may potentially mitigate memory impairment.