Physical activity and risk of cognitive impairment and dementia in elderly persons. (Abstracts of Current Literature).

Laurin D, Verreault R, Lindsay J, et al (Laval University Geriatric Research Unit and Department of Social and Preventative Medicine, Sainte-Foy, Quebec; Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, Ontario; Department of Community Health and Epidemiology, Dalhousie University, Halifax, Nova Scotia), Arch Neurol. 2001;58:498-504.

Using a prospective, cohort design, this study examined the association between physical activity and the occurrence of cognitive impairment and dementia 5 years later. Data were collected on randomly selected Canadian men and women at least 65 years of age who participated in the 1991-1992 Canadian Study of Health and Aging, a national, multicenter study examining prevalence, incidence, and risk factors for dementia and Alzheimer disease in Canada. Follow-up data were recorded in the 1996-1997 phase.

Cognitive impairment and dementia were identified using the Modified Mini-Mental State Examination and a neuropsychological test battery. Diagnoses of cognitive ability were determined by a neuropsychologist and a physician using 1 of 5 possible classifications: "no dementia," "cognitive impairment-no dementia," "Alzheimer disease (probable or possible)," "vascular dementia," or "other specific and unclassified dementia." Physical activity level was determined by a questionnaire that measured frequency and intensity of exercise and was classified as "high" (3 or more times per week at an intensity greater than walking), "moderate" (3 or more times per week at an intensity equal to walking), "low" (all other combinations of intensity and frequency), or "none."

Of the 9,008 initial participants, 6,434 were determined by the researchers to be free of cognitive impairment and, of this group, 4,615 were available for follow-up examination 5 years later. Consensus diagnoses of cognitive ability were rendered without knowledge of the previous classification. Multivariate logistic regression models accounted for confounding variables such as age, education, and family history of dementia. After 5 years, 84% of the initial 4,615 participants were classified "no impairment" (n=3,894), 9% were classified "cognitive impairment-no dementia" (n=436), 4% were classified as having Alzheimer disease (n=194), and 2% were classified as having dementia of any type (n=91).

According to the results, physical activity was associated with lower risks of cognitive impairment (odds ratio [OR]=0.58, 95% confidence interval [CI]=0.41, 0.83), Alzheimer disease (OR-0.50, 95% CI=0.28, 0.90), and dementia of any type (OR=0.63, 95% CI-0.40, 0.98) compared with no physical activity. Significant trends toward lower risk with higher levels of activity supported a dose-response relationship. Comparisons by sex revealed that women had a 50% reduction in the chance of developing cognitive impairment or dementia and a 60% reduction for Alzheimer disease with the highest level of physical activity, whereas men had no significant associations between cognitive impairment, dementia, or Alzheimer disease and physical activity.

The authors concluded that their data suggested that regular physical activity offered a protective benefit against the risk of developing cognitive impairment or dementia, especially in women. They suggested that possible mechanisms for this effect were related to the cerebral effects of physical activity, including increased cerebral blood flow, reduced lipid levels, and increased cerebral metabolic supply and demand.

James W Bellew, PT, EdD
Louisiana State University Health
Sciences Center
Shreveport, La