A study involving 68 healthy older adults (65-85) has compared brain activity among four groups, determined whether or not they carry the Alzheimer’s gene ApoE4 and whether their physical activity is reported to be high or low. The participants performed a task involving the discrimination of famous people, which engages 15 different functional regions of the brain. Among those carrying the gene, those with higher physical activity showed greater activation in many regions than those who were sedentary. Moreover, physically active people with the gene had greater brain activity than physically active people without the gene.
And adding to the evidence supporting the potential for exercise to lower the risk of dementia, another recent study has found that after ten years exercise (in terms of the number of different types of exercises performed and number of exercise sessions lasting at least 20 minutes) was inversely associated with the onset of cognitive impairment. The study used data from the National Long Term Care Survey.
 . Interactive effects of physical activity and APOE-[epsilon]4 on BOLD semantic memory activation in healthy elders. NeuroImage [Internet]. 2011 ;54(1):635 - 644. Available from: http://www.sciencedirect.com/science/article/B6WNP-50PJWV6-2/2/59ddd28ab1b310c33701fa41a478207d
 . Exercise and cognition: Results from the National Long Term Care Survey. Alzheimer's and Dementia [Internet]. 2010 ;6(6):448 - 455. Available from: http://www.alzheimersanddementia.com/article/S1552-5260(10)00060-9/abstract