In a 44-year-long study involving women, high midlife cardiovascular fitness was related to a decreased risk in dementia. The study found a dose-dependent relationship between fitness level and dementia risk. Those with a high cardiovascular fitness level had only a 5% incidence of all-cause dementia by the end of the study, as compared with 25% for medium fitness, and 32% for low fitness. Furthermore, for those who did develop dementia, the onset was an average of five years later in the high fitness group, than in the medium fitness group. The average age of dementia was 11 years higher in women with a higher fitness level than those with a medium fitness level.
Cardiovascular fitness levels were measured at the start of the study using a stationary bicycle test that incrementally increased workload, in which participants cycled to exhaustion. Dementia assessments were administered to the participants every 5-10 years thereafter. The women who had the highest fitness levels also on average had higher wine consumption, their own income, and less hypertension compared with the medium or low fitness groups. Although this study only involved women, similar conclusions can be extrapolated to men. A Swedish study that tested cardiovascular fitness utilizing the bicycle test in 18-year-old men, found an increased risk in the onset of dementia occurring among medium fitness levels as compared with highly fit men, and further increased the risk in those with low fitness levels. A very high dementia incidence was found particularly in participants who could not complete the bicycle test before reaching a submaximal load.
Although the findings were not causative, there is a definitive association between higher cardiovascular fitness and a lower risk for dementia. Physiologically speaking, those who are the most fit, have a greater amount of oxygen circulating through their bodies. Higher oxygenation to muscles increase endurance and performance. Similarly, the same effect can be hypothesized to apply to brain function, as many associative studies have supported. In short, increasing your cardiovascular fitness level will almost surely enhance your mental function. Yet another pillar for the benefits of exercise.