Exercise linked to big drop in dementia risk
22:00 16 January 2006
NewScientist.com news service
Gaia Vince
Paul Crane from the University of Washington
Centers for Disease Control and Prevention in Atlanta, Georgia
Annals of Internal Medicine
Regular exercise may reduce the risk of dementia and Alzheimer’s disease in the elderly by as much as 40%, according to a new study. And the effect is even more pronounced for those who are more frail, say the researchers.
The US team, at Group Health Cooperative in Seattle, studied a group of 1740 people aged 65 or over, all of whom began the study with good cognitive function.
The participants reported how many days per week they had exercised for 15 minutes or more, in activities varying from walking to callisthenics to swimming. Their physical function was also recorded, including grip strength and walking speed. Each was evaluated again every two years and tests were performed to determine whether they had developed dementia.
After six years, 158 people in the group had developed dementia, and 107 of these had Alzheimer’s. But those who had exercised at least three times a week were on average 38% less likely to have developed dementia than those exercising less than three times a week.
Unknown mechanism
“Those who had scored the lowest on the physical function tests, showed the most marked reduction in risk of dementia if they exercised,” says Paul Crane, one of the research team, from the University of Washington in Seattle. Amongst those with good levels of exercise, “people who scored 10 out of 16 in the physical tests had an average 42% reduction in risk of dementia, compared to 25% for those who scored 12 out of 16."
He adds: “Our study group was fairly fit and healthy compared to the average population, so the benefits of exercise could be even greater for less fit people.”
Crane says the biological mechanism behind the results is unknown, but that it may result from exercise causing a reduction in vascular disease.
“It could be that these people are still developing plaques [deposits in the brain which cause Alzheimer’s] but exercise is stopping them from having strokes – so they are not showing clinical symptoms of dementia,” he told New Scientist.
Subclinical deterioration
Other studies into the relationship between exercise and dementia have shown mixed results. But previous studies have not excluded the possibility that participants with lower exercise levels at the start undertook less physical activity because they were already suffering from early, subclinical cognitive deterioration.
Laura Podewils at the Centers for Disease Control and Prevention in Atlanta, Georgia, US, and co-author of an editorial accompanying the study, says the team behind the new research made a great effort to avoid this bias. "It is also the first study to report an interaction between the level of physical function and physical activity and dementia risk,” she says.
However, Podewils points out that it remains uncertain whether this association is causal or whether physical activity is more likely among people with other behaviours that reduce dementia risk.
“People who exercise tend to be more socially active, which enhances cognitive activity. We need randomised trials to establish the relationship, but nonetheless exercise undoubtedly has extensive health benefits,” she says.
Journal reference: Annals of Internal Medicine (vol 144, p 73)
The Human Brain - With one hundred billion nerve cells, the complexity is mind-boggling. Learn more in our cutting edge special report.
re frail, say the researchers.
The US team, at Group Health Cooperative in Seattle, studied a group of 1740 people aged 65 or over, all of whom began the study with good cognitive function.
The participants reported how many days per week they had exercised for 15 minutes or more, in activities varying from walking to callisthenics to swimming. Their physical function was also recorded, including grip strength and walking speed. Each was evaluated again every two years and tests were performed to determine whether they had developed dementia.
After six years, 158 people in the group had developed dementia, and 107 of these had Alzheimer’s. But those who had exercised at least three times a week were on average 38% less likely to have developed dementia than those exercising less than three times a week.
Unknown mechanism
“Those who had scored the lowest on the physical function tests, showed the most marked reduction in risk of dementia if they exercised,” says Paul Crane, one of the research team, from the University of Washington in Seattle. Amongst those with good levels of exercise, “people who scored 10 out of 16 in the physical tests had an average 42% reduction in risk of dementia, compared to 25% for those who scored 12 out of 16."
He adds: “Our study group was fairly fit and healthy compared to the average population, so the benefits of exercise could be even greater for less fit people.”
Crane says the biological mechanism behind the results is unknown, but that it may result from exercise causing a reduction in vascular disease.
“It could be that these people are still developing plaques [deposits in the brain which cause Alzheimer’s] but exercise is stopping them from having strokes – so they are not showing clinical symptoms of dementia,” he told New Scientist.
Subclinical deterioration
Other studies into the relationship between exercise and dementia have shown mixed results. But previous studies have not excluded the possibility that participants with lower exercise levels at the start undertook less physical activity because they were already suffering from early, subclinical cognitive deterioration.
Laura Podewils at the Centers for Disease Control and Prevention in Atlanta, Georgia, US, and co-author of an editorial accompanying the study, says the team behind the new research made a great effort to avoid this bias. "It is also the first study to report an interaction between the level of physical function and physical activity and dementia risk,” she says.
However, Podewils points out that it remains uncertain whether this association is causal or whether physical activity is more likely among people with other behaviours that reduce dementia risk.
“People who exercise tend to be more socially active, which enhances cognitive activity. We need randomised trials to establish the relationship, but nonetheless exercise undoubtedly has extensive health benefits,” she says.
Journal reference: Annals of Internal Medicine (vol 144, p 73)
The Human Brain - With one hundred billion nerve cells, the complexity is mind-boggling. Learn more in our cutting edge special report. |
