Studies Show Physical Activity Delays Onset of Dementia

SEATTLE – Evidence is beginning to suggest that exercise can at least forestall Alzheimer's disease, Dr. Eric B. Larson said at the annual scientific meeting of the American Geriatrics Society.

“We now see association studies of physical activity showing a pretty convincing relationship with a delayed onset of dementia,” said Dr. Larson, the executive director of the Center for Health Studies of the Group Health Cooperative, Seattle. “I don't think we are preventing this disease from ever happening,” he added. “What we're doing is delaying it.”

Four observational studies have now shown, with consistency, a 30%–40% reduction in the incidence of Alzheimer's disease when people get regular exercise, Dr. Larson noted.

Some might find it implausible that physical exercise could affect the brain, cognitive function, and decline, since it has been thought that the brain does not develop after a young age, Dr. Larson noted. It turns out that animal experiments show that new neurons do form in the adult brain.

“Neurogenesis is possible at almost any phase of development, at least in animals,” he said.

And then, there is the human study.

In a study of humans who used functional magnetic resonance imaging, the investigators found that aerobic physical fitness measured on a treadmill correlated with frontal, parietal, and temporal lobe tissue density, such that better fitness meant higher density, which indicates less age-related loss (J. Gerontol. A Biol. Sci. Med. Sci. 2003;58:176–80).

In his own study, Dr. Larson looked at 2,581 individuals, who were aged 65 years or older, without dementia. They were tested for cognitive functioning and interviewed about exercise habits every 2 years, starting in 1994–1996. For the analysis, the investigators threw out those individuals who scored in the bottom quartile of subjects on the cognitive testing, on the grounds that they might be persons already showing some dementia-associated decline (Ann. Intern. Med. 2006;144:73–81).

With an average follow-up of 6.2 years, during which time 158 subjects developed dementia, the researchers found that those subjects who exercised three or more times per week had a 40% reduction in the risk of developing dementia, compared with those who exercised less than three times per week.

The incidence rates of dementia were 13/1,000 person-years for those who exercised three or more times per week, compared with 19.7/1,000 person-years for those who exercised less than three times per week.

Exercise was defined as the number of days during the past year that the subjects had engaged in walking, hiking, bicycling, aerobics or calisthenics, swimming, water aerobics, weight training, stretching, or other exercise, for at least 15 minutes at a time. About 60% of those who developed dementia had developed Alzheimer's disease.

The interesting part of the findings was that those subjects who had the lowest physical performance benefited the most from exercise, Dr. Larson said.

All of the prevention was in the people in the lowest third on physical performance measures.

SEATTLE – Evidence is beginning to suggest that exercise can at least forestall Alzheimer's disease, Dr. Eric B. Larson said at the annual scientific meeting of the American Geriatrics Society.

“We now see association studies of physical activity showing a pretty convincing relationship with a delayed onset of dementia,” said Dr. Larson, the executive director of the Center for Health Studies of the Group Health Cooperative, Seattle. “I don't think we are preventing this disease from ever happening,” he added. “What we're doing is delaying it.”

Four observational studies have now shown, with consistency, a 30%–40% reduction in the incidence of Alzheimer's disease when people get regular exercise, Dr. Larson noted.

Some might find it implausible that physical exercise could affect the brain, cognitive function, and decline, since it has been thought that the brain does not develop after a young age, Dr. Larson noted. It turns out that animal experiments show that new neurons do form in the adult brain.

“Neurogenesis is possible at almost any phase of development, at least in animals,” he said.

And then, there is the human study.

In a study of humans who used functional magnetic resonance imaging, the investigators found that aerobic physical fitness measured on a treadmill correlated with frontal, parietal, and temporal lobe tissue density, such that better fitness meant higher density, which indicates less age-related loss (J. Gerontol. A Biol. Sci. Med. Sci. 2003;58:176–80).

In his own study, Dr. Larson looked at 2,581 individuals, who were aged 65 years or older, without dementia. They were tested for cognitive functioning and interviewed about exercise habits every 2 years, starting in 1994–1996. For the analysis, the investigators threw out those individuals who scored in the bottom quartile of subjects on the cognitive testing, on the grounds that they might be persons already showing some dementia-associated decline (Ann. Intern. Med. 2006;144:73–81).

With an average follow-up of 6.2 years, during which time 158 subjects developed dementia, the researchers found that those subjects who exercised three or more times per week had a 40% reduction in the risk of developing dementia, compared with those who exercised less than three times per week.

The incidence rates of dementia were 13/1,000 person-years for those who exercised three or more times per week, compared with 19.7/1,000 person-years for those who exercised less than three times per week.

Exercise was defined as the number of days during the past year that the subjects had engaged in walking, hiking, bicycling, aerobics or calisthenics, swimming, water aerobics, weight training, stretching, or other exercise, for at least 15 minutes at a time. About 60% of those who developed dementia had developed Alzheimer's disease.

The interesting part of the findings was that those subjects who had the lowest physical performance benefited the most from exercise, Dr. Larson said.

All of the prevention was in the people in the lowest third on physical performance measures.

SEATTLE – Evidence is beginning to suggest that exercise can at least forestall Alzheimer's disease, Dr. Eric B. Larson said at the annual scientific meeting of the American Geriatrics Society.

“We now see association studies of physical activity showing a pretty convincing relationship with a delayed onset of dementia,” said Dr. Larson, the executive director of the Center for Health Studies of the Group Health Cooperative, Seattle. “I don't think we are preventing this disease from ever happening,” he added. “What we're doing is delaying it.”

Four observational studies have now shown, with consistency, a 30%–40% reduction in the incidence of Alzheimer's disease when people get regular exercise, Dr. Larson noted.

Some might find it implausible that physical exercise could affect the brain, cognitive function, and decline, since it has been thought that the brain does not develop after a young age, Dr. Larson noted. It turns out that animal experiments show that new neurons do form in the adult brain.

“Neurogenesis is possible at almost any phase of development, at least in animals,” he said.

And then, there is the human study.

In a study of humans who used functional magnetic resonance imaging, the investigators found that aerobic physical fitness measured on a treadmill correlated with frontal, parietal, and temporal lobe tissue density, such that better fitness meant higher density, which indicates less age-related loss (J. Gerontol. A Biol. Sci. Med. Sci. 2003;58:176–80).

In his own study, Dr. Larson looked at 2,581 individuals, who were aged 65 years or older, without dementia. They were tested for cognitive functioning and interviewed about exercise habits every 2 years, starting in 1994–1996. For the analysis, the investigators threw out those individuals who scored in the bottom quartile of subjects on the cognitive testing, on the grounds that they might be persons already showing some dementia-associated decline (Ann. Intern. Med. 2006;144:73–81).

With an average follow-up of 6.2 years, during which time 158 subjects developed dementia, the researchers found that those subjects who exercised three or more times per week had a 40% reduction in the risk of developing dementia, compared with those who exercised less than three times per week.

The incidence rates of dementia were 13/1,000 person-years for those who exercised three or more times per week, compared with 19.7/1,000 person-years for those who exercised less than three times per week.

Exercise was defined as the number of days during the past year that the subjects had engaged in walking, hiking, bicycling, aerobics or calisthenics, swimming, water aerobics, weight training, stretching, or other exercise, for at least 15 minutes at a time. About 60% of those who developed dementia had developed Alzheimer's disease.

The interesting part of the findings was that those subjects who had the lowest physical performance benefited the most from exercise, Dr. Larson said.

All of the prevention was in the people in the lowest third on physical performance measures.