Thorleif Etgen, from Technische Universitat (Munich, Germany), and colleagues studied 3,903 subjects, ages 55 and older when enrolled in the study, following them for a two-year period. 
Each was categorized as to physical activity (no activity, moderate activity [<3 times/wk], and high activity [3 times/wk]), and cognitive function was evaluated.  At the beginning of the study, 418 participants (10.7%) had cognitive impairment. After two years, 207 (5.9%) of the remaining 3,485 unimpaired study participants developed cognitive impairment. 
Observing that the incidence of new cognitive impairment among participants with no, moderate and high activity at baseline was 13.9%, 6.7%  and 5.1%, respectively, the researchers urge that: “Moderate or high physical activity is associated with a reduced incidence of cognitive impairment after 2 years in a large population-based cohort of elderly subjects.”