The effect of midlife physical activity on cognitive function among older adults: AGES–Reykjavik Study..

Chang M, Jonsson PV, Snaedal J, Bjornsson S, Saczynski JS, Aspelund T, Eiriksdottir G, Jonsdottir MK, Lopez OL, Harris TB, Gudnason V, Launer LJ.  J Gerontol A Biol Sci Med Sci. 2010 Dec;65(12):1369-74.