Chronic exercise in brain diseases

Given the growing segment of the aging population, interest in lifestyle factors and interventions that may stimulate cognitive function in aging and may reduce the risk of age-related neurodegenerative disorders, such asAlzheimer’s disease, is increasing. The claim that physical activity enhances brain function, that is cognitive function, and is therefore associated with a reduced risk of neurodegenerative disease is supported by different kinds of research, including observational studies, animal experimental studies and human intervention studies (Kramer and Erickson, 2007). Several epidemiological studies show a positive relationship between the level of physical activity and cognitive functioning (Fratiglioni et al., 2004; Laurin et al., 2001; Rovio et al., 2005; Van Gelder et al., 2004). In one prospective cohort study, in which participantswere assessed at baseline and after five years, itwas observed that physical activity of a high intensity was associatedwith a reduced risk of cognitive impairment, particularly in women (Laurin et al., 2001). A comparable association has been reported in men. Over a 10 year time interval, longer periods of physical activity and increased intensity of the activity were associated with less decline in cognitive functioning (Van Gelder et al., 2004). Physical activity does not necessarily have to be vigorous to be associated with cognition (Yaffe et al., 2001). In community-dwelling older women, it was shown that those who walked most blocks a week revealed less cognitive decline (Yaffe et al., 2001). The observational nature of these epidemiological studies, however, cannot establish causation (Fratiglioni et al., 2004). There have been an increasing number of intervention studies in which older people participated in a physical activity programme and cognitive measures were assessed before and after the intervention. Results of these studies have been mixed, however most studies revealed positive effects (Kramer and Erickson, 2007). A meta-analysis showed that in older people, executive functions (EF), like planning and organizing, benefited most from the physical activity intervention (Colcombe and Kramer, 2003). Only a few studies investigated the effects of the physical activity intervention on human brain