A four-year study involving 716 elderly (average age 82) has revealed that those who were most physically active were significantly less likely to develop Alzheimer’s than those least active. The study is unique in that, in addition to self-reports of physical and social activity, activity was objectively measured (for up to 10 days) through a device worn on the wrist. This device (an actigraph) enabled everyday activity, such as cooking, washing the dishes, playing cards and even moving a wheelchair with a person's arms, to be included in the analysis.
Cognitive performance was assessed annually. Over the study period, 71 participants (10%) developed Alzheimer’s.
The study found that those in the bottom 10% of daily physical activity were more than twice as likely (2.3 times) to develop Alzheimer's disease as those in the top 10%. Those in the bottom 10% of intensity of physical activity were almost three times (2.8 times) as likely to develop Alzheimer's disease as people in the top 10%.
Moreover, the level of activity was associated with the rate of cognitive decline.
The association remained after motor function, depression, chronic health conditions, and APOE gene status were taken into account.
The findings should encourage anyone who feels that physical exercise is beyond them to nevertheless engage in milder forms of daily activity.
Another recent study, involving 331 cognitively healthy elderly, has also found that higher levels of physical activity were associated with better cognitive performance (specifically, a shorter time to complete the Trail-making test, and higher levels of verbal fluency) and less brain atrophy. Activity levels were based on the number of self-reported light and hard activities for at least 30 minutes per week. Participants were assessed in terms of MMSE score, verbal fluency, and visuospatial ability.
 . Total Daily Physical Activity and the Risk of AD and Cognitive Decline in Older Adults. Neurology [Internet]. 2012 ;78(17):1323 - 1329. Available from: http://www.neurology.org/content/78/17/1323
 Association between physical activity and brain health in older adults. Neurobiology of Aging [Internet]. Submitted . Available from: http://www.sciencedirect.com/science/article/pii/S0197458012002618