Published in Neurology Clinical Practice, a systematic review of the literature examined the influence of exercise on cognitive function in older adults.1
The findings they showed a significant correlation with total hours exercised. At least 52 hours of resistance, aerobic, mind-body, or any combination of these exercises over 6 months had a positive effect on global cognition in this study.
Gomes-Osman J, Cabral DF, Morris TP, et al. Exercise for cognitive brain health in aging: A systematic review for an evaluation of dose. Neurology Clinical Practice. May 30, 2018. http://cp.neurology.org/content/early/2018/05/30/CPJ.0000000000000460. Accessed June 19, 2018.