Evidence from multiple observational studies suggests an association between physical activity and a reduced risk of dementia.
A prospective cohort study published in the Archives of Internal Medicine (2006; 144(2):73–81) examined exercise habits in 1,740 adults over the age of 65. Over the course of follow-up, participants who exercised three or more times per week were found to have a lower incidence of dementia compared with those who exercised less frequently.
The projected burden of dementia has been addressed in population-level research. The Lancet published the “Global Prevalence of Dementia: A Delphi Consensus Study” (2005; 366(9503):2112–2117), which estimated that the number of people with dementia in developed countries would double between 2001 and 2040. At the time of publication, dementia affected more than 23 million people worldwide, with approximately 4.6 million new cases each year, corresponding to a new case every seven seconds.
Additional cohort data were reported in The Journals of Gerontology Series A (2008; 63(5):529–535), which examined 2,263 men aged 71 to 92 years. This study also found that higher levels of physical activity were associated with a lower likelihood of developing dementia.
Further evidence comes from a study published in the Archives of Neurology (March 2001; 58:498–504), which followed 9,008 men and women over the age of 65 who were free of cognitive impairment at baseline. Of these participants, 4,615 were available for five-year follow-up. During that period, 436 individuals developed cognitive impairment, and 285 developed dementia. Regular physical activity was associated with a reduced risk of both cognitive impairment and dementia, with a graded relationship observed: greater levels of activity were associated with lower incidence.
Short-term effects of exercise on cognitive performance have also been explored. A report presented at the annual meeting of the Society of Psychophysiological Research in Montreal, Canada (October 18, 2001) evaluated 20 adults aged 18 to 24 years. Participants completed cognitive tests before and after 30 minutes of running, with brain activity measured using electroencephalography (EEG). Post-exercise testing showed faster decision-making, accompanied by changes in brain wave activity.
