Via EurekAlert!: "Daily physical exercise may reduce the risk of Alzheimer's disease, even in people over the age of 80 ... The study showed that not only exercise but also activities such as cooking, washing the dishes and cleaning are associated with a reduced risk of Alzheimer's disease. These results provide support for efforts to encourage physical activity in even very old people who might not be able to participate in formal exercise but can still benefit from a more active lifestyle. ... For the study, a group of 716 people with an average age of 82 wore an actigraph, a device that monitors activity, on their non-dominant wrist continuously for 10 days. All exercise and non-exercise was recorded. They also were given annual tests during the four-year study that measured memory and thinking abilities. During the study, 71 people developed Alzheimer's disease. ... The research found that people in the bottom 10 percent of daily physical activity were more than twice as likely to develop Alzheimer's disease as people in the top 10 percent of daily activity. The study also showed that those people in the bottom 10 percent of intensity of physical activity were almost three times as likely to develop Alzheimer's disease as people in the top 10 percent of intensity of physical activity."