"This is the first study to follow a large group of individuals for this long a period of time," Zaldy Tan said.
"It suggests that lowering the risk for dementia may be one additional benefit of maintaining at least moderate physical activity, even into the eighth decade of life."
Framingham Study Shows Physical Activity Lowers Risk of Dementia, Especially in Men
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Several long-term epidemiological studies have related physical activity and cognitive decline, dementia and/or Alzheimer's disease, although the results of published research studies thus far are not entirely consistent and several large studies failed to show an association.
Most of these studies followed participants for less than six years or had significant loss to follow-up. Still needed are studies including long-term follow-up in older persons in age brackets at higher risk of incident Alzheimer's to elucidate the true relationship.
One such long-term trial is the Framingham Study, a population-based study that has followed participants residing in the town of Framingham, Massachusetts since 1948 for cardiovascular risk factors, and is now also tracking cognitive performance. Framingham is widely acknowledged as a premier longitudinal study; it has continued to yield valuable information for more than 40 years.
Zaldy Tan, MD, MPH, of Brigham and Women's Hospital, GRECC, VA Boston, and Harvard Medical School, and colleagues estimated the levels of 24-hour physical activity of more than 1,200 elderly participants from the Framingham Study (742 female; age 76 +\-5) during the study's 20th examination cycle (1986-87) and followed them for the development of dementia. They divided the participants into five groups based on level of physical activity, from lowest (Q1) to highest (Q5).
Over two decades of follow-up (mean 9.9 +/-5 years), 242 participants developed dementia (of which 193 were Alzheimer's). The researchers found that participants who performed moderate to heavy levels of physical activity had about a 40 percent lower risk of developing any type of dementia.
Further, people who reported the lowest levels of physical activity were 45 percent more likely to develop any type of dementia compared to those who reported higher levels of activity. Similar results were seen when analyses were limited to Alzheimer's alone. Analyses showed that the observed associations were largely evident in men in the study.
"This is the first study to follow a large group of individuals for this long a period of time," Tan said. "It suggests that lowering the risk for dementia may be one additional benefit of maintaining at least moderate physical activity, even into the eighth decade of life."
Zaldy S. Tan, et al. Physical Activity and the Risk of Dementia: The Framingham Study. (Funded by: National Institutes of Health; National Heart, Lung, and Blood Institute; National Institute on Aging)
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Original content Bob DeMarco, the Alzheimer's Reading Room