Chronic physical activity and the prevention of Alzheimer's disease.

The growing population of older adults and the lack of cure for Alzheimer's disease (AD) has resulted in researchers identifying modifiable lifestyle factors that might prevent or slow the progression of the disease. Prospective studies exploring the relationship between baseline physical activity (PA) and the subsequent risk of a diagnoses of AD and randomized controlled trials (RCTs) testing the effects of aerobic exercise (AE) and resistance exercise (RE) on cognitive performance, blood-based biomarkers of AD, and neuroimaging measures of brain health provide some intriguing results. Exemplars of these studies and results from meta-analytic reviews (when available) are presented to provide an overview of the state of the science. In general, results from prospective studies show that PA is protective, and results from RCTs show that AE improves cognitive performance by older adults who are cognitively normal and by those with mild cognitive impairment. Promising results have been observed for AE on measures of brain health, and studies exploring the effects on biomarkers have yielded some intriguing results but are less consistent to date. Studies testing the effects of RE also find benefits for cognitive performance by older adults and consistently show improvements in brain health. In conclusion, results from prospective studies and RCTs demonstrate the potential of exercise to improve cognition, brain health, and, to a lesser extent, blood-based biomarkers. Future research linking the magnitude of the findings from RCTs with evidence from prospective studies will advance our understanding of the potential of exercise to reduce the risk of AD.