Protective activities include washing dishes, cooking, cleaning, gardening — even playing cards. People who scored in the bottom 10% of physical activity were more than twice as likely to develop Alzheimer's. Study participants did not have dementia at the start of the four-year study, which is part of the ongoing Memory and Aging Project at Rush University Medical Center in Chicago. "The implication of this study is really astounding," says physician Aron Buchman, the lead author. "Exercise is good, without a doubt, but this study is about more than exercise. Older people who might not be able to exercise can tailor activities that are right for them." There is no cure or drug to delay the onset of Alzheimer's disease, which affects about 5 million people in the USA; numbers are expected to triple as Baby Boomers get older. Aging is the main risk factor.
During the study, 71 of the 716 study participants developed Alzheimer's. Study authors say this is the first study to use an objective measurement of all physical activity in addition to self-reports. Participants wore an actigraph on their wrists to assess levels of activity. The mean score for participants was 3.3 hours per week. Intensity of exercise also mattered: People in the bottom 10% of intensity of physical activity were almost three times as likely to develop Alzheimer's. The study is the latest evidence that physical activity, even in later years, aids in delaying Alzheimer's. The study did not attempt to measure which activities were most helpful. "We've known that muscle activity generates neurons in the brain, but this study gives us additional motivation," says physician Gary Kennedy, director of geriatric psychiatry at Montefiore Medical Center in New York, who was not associated with the study. "It shows you don't have to go to the gym. Older people very often don't want to do that."
Results did not vary by age, sex or education. The authors also looked at chronic health and genetic factors. Among the findings:
•Body mass index, depressive symptoms or vascular risk factors did not change the association between activities and risk.
•The gene APOE4, which puts people at higher risk for developing Alzheimer's, did not change the results. Alzheimer's develops for years prior to symptoms occurring, notes Kennedy. The authors tried to control for that possibility by administering baseline cognitive tests. "This is an important message for society as the largest growing segment of our population is old people," says Buchman. "We need to be encouraging physical activities even in very old individuals, even if their health doesn't allow them to take part in fitness programs." In an accompanying editorial, the authors cite physical activity as a promising, low-cost, easily accessible and side-effect-free means to prevent Alzheimer's.