It is well established that more physical activity correlates with reduced risk of mortality and age-related disease. The accumulated epidemiological evidence is mountainous in scope, and includes countless studies similar to the one noted here. It is hard, however, to prove causation in human studies. Are people more active because they happen to be more robustly resistant to the declines of aging for reasons entirely unrelated to physical activity, for example? In mice, yes, one can create groups at various levels of exercise and show that those who exercise to a greater degree have a longer span of healthy life (though not a longer life overall). The direction of causation can be established there, and exercise produces better health and lesser degrees of decline in aging. Health advice for humans leans heavily on the causation established in mice and other mammals. Reasonably so, I would say.
Keeping physically and mentally active in middle age may be tied to a lower risk of developing dementia decades later. The study involved 800 Swedish women with an average age of 47 who were followed for 44 years. At the beginning of the study, participants were asked about their mental and physical activities. Mental activities included intellectual activities, such as reading and writing; artistic activities, such as going to a concert or singing in a choir; manual activities, such as needlework or gardening; club activities; and religious activity.
Participants were given scores in each of the five areas based on how often they participated in mental activities, with a score of zero for no or low activity, one for moderate activity and two for high activity. For example, moderate artistic activity was defined as attending a concert, play or art exhibit during the last six months, while high artistic activity was defined as more frequent visits, playing an instrument, singing in a choir or painting. The total score possible was 10.
Participants were divided into two groups. The low group, with 44 percent of participants, had scores of zero to two and the high group, with 56 percent of participants, had scores of three to 10. For physical activity, participants were divided into two groups, active and inactive. The active group ranged from light physical activity such as walking, gardening, bowling or biking for a minimum of four hours per week to regular intense exercise such as running or swimming several times a week or engaging in competitive sports. A total of 17 percent of the participants were in the inactive group and 82 percent were in the active group.
During the study, 194 women developed dementia. Of those, 102 had Alzheimer's disease, 27 had vascular dementia, and 41 had mixed dementia, which is when more than one type of dementia is present, such as the plaques and tangles of Alzheimer's disease along with the blood vessel changes seen in vascular dementia. The study found that women with a high level of mental activities were 46 percent less likely to develop Alzheimer's disease and 34 percent less likely to develop dementia overall than the women with the low level of mental activities. The women who were physically active were 52 percent less likely to develop dementia with cerebrovascular disease and 56 percent less likely to develop mixed dementia than the women who were inactive.