Physical Activity Linked to Lower Risk of Dementia

Medscape Medical News from the Alzheimer's Association International Conference on Alzheimer's Disease (ICAD) 2010

Susan Jeffrey

July 12, 2010 (Honolulu, Hawaii) — A new analysis from the Framingham Study suggests moderate to heavy physical activity is associated with a reduced risk for dementia during more than 20 years of follow-up.

Compared with those with lower levels of activity, participants reporting moderate to heavy physical activity had a 45% lower risk for dementia over time.

"A reduced risk of dementia may be one of the additional health benefits that can actually be derived from maintaining at least moderate physical activity," lead author Zaldy Tan, MD, MPH, from the Brigham and Women's Hospital, VA Boston, and Harvard Medical School, in Massachusetts, concluded.
Dr. Zaldy Tan

Dr. Tan presented the results here at the Alzheimer's Association International Conference on Alzheimer's Disease 2010.

Divergent Findings

Previous findings from the Framingham original cohort have already shown moderate or high physical activity to be associated with a number of positive outcomes, including a reduced risk for stroke and cardiovascular disease, higher high-density lipoprotein cholesterol levels, a reduced risk for colon cancer, and lower overall rates of mortality, Dr. Tan noted.

"Interestingly, while there are many potentially modifiable risk factors that have been linked with Alzheimer's disease and dementia, physical activity seems to be one that is fairly consistent in being shown to be related to the risk of dementia," he said. A recent review showed that 20 of 24 population-based studies showed a link between physical activity and reduced risk for dementia or cognitive decline.

Still, Dr. Tan added, the evidence is not entirely consistent. "There are some studies that seem to show no relationship between physical activity and dementia," he said, including the Bronx Aging Study, the Religious Orders Study, and the Radiation Effects Research Foundation Study.

The present investigation then looked at this relationship in the Framingham Study original cohort — a longitudinal community-based sample of 5209 men and women living in Framingham, Massachusetts, that has been evaluated every 2 years since 1948 for cardiovascular risk factors. A dementia study began in 1975, with the administration of a battery of neuropsychological tests, and 3349 of the original participants free of dementia at that time were enrolled and subsequently assessed every 2 years.

In 1986 to 1987, a survey was introduced to calculate a daily physical activity index (PAI) based on estimated hours spent performing physical activity and weighting each activity by an assigned caloric equivalent. The study population for this current study, then, includes those participants who were both free of dementia in 1986 and 1987 and who had a PAI available, for a total of 1211 Framingham study participants.

Participants were asked to estimate the amount of time they spent in various activities, ranging from sleep and sedentary states; to slight physical activity, such as standing and walking; to moderate activity, including things like housework, climbing stairs, or light sports like golf or bowling; to heavy activity, including heavy household work or more intensive exercise such as jogging.

During a mean follow-up of 9.9 ± 5.5 years, ranging from 0 to 21 years, 242 participants developed dementia. Of these, 193 cases were Alzheimer's disease, defined according to Diagnostic and Statistical Manual of Mental Disorders, 4th Edition/National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association criteria.

"What we found is that participants who spent at least 1 hour per day of moderate or heavy physical activity had a 45% lower risk of developing dementia," Dr. Tan said.