Fit Bodies Keep Minds Sharp into Later Years

October 10, 2006

ENDIBURGH, Scotland -- Fitness helps keep minds agile as time goes by, according to European studies.

EDINBURGH, Scotland, Oct. 10 -- Fit bodies help keep minds agile as time goes by.

So concluded researchers in Scotland and France who studied the mind-body connection, and reported their findings in two studies in the Oct. 9 issue of Neurology.

Scots who underwent cognitive testing at the age of 11 in 1932 and were tested again nearly seven decades later had better cognitive function if they were in good physical shape, supporting the idea that "physical fitness is associated with more successful cognitive aging," wrote psychologist Ian J. Deary, Ph.D., of the University of Edinburgh here, and colleagues.

"The important result of the study is that fitness contributes to better cognitive ability in old age," Dr. Deary said. "Thus, two people starting out with the same IQ at age 11, the fitter person at age 79 will, on average, have better cognitive function."

In a separate study, French researchers looked at the problem the other way around and found that the higher the body mass index, the lower the cognitive performance both at baseline and at five-year follow-up.

They did not, however, find an association between change in BMI and cognitive performance, noted epidemiologist Maxime Cournot, M.D., of Toulouse University Hospital, and colleagues.

Dr. Deary and colleagues in Edinburgh, Glasgow, and Aberdeen took advantage of a cognitive data gold mine -- test scores of 87,498 people who were born in 1921 and were attending school in Scotland on June 1, 1932, when they were assessed as part of the Scottish Mental Survey of 1932.

A total of 460 surviving participants in the 1932 survey were tested at age 79 on the same general cognitive test, called the Moray House test. The 71-item test primarily measures verbal reasoning, but also contains numerical and spatial items and other measures of cognitive ability. The test is equivalent in validity to the Stanford-Binet test for age 11, and the Raven's Progressive Matrices for age 79, the authors wrote.

The participants, all living in the community independently, traveled to the test site on their own. They were tested for physical fitness with measures of grip strength, six-meter walk time, and lung function, assessed as forced expiratory volume from the lungs in one second (FEV1).

The authors also used logistic regression analysis to control for variables that included gender, education, socioeconomic status, smoking, co-morbidities, and apolipoprotein-E4 (APOE ?4) allele.

They found that "physical fitness, as defined by a latent trait of time to walk six meters, grip strength, and FEV1, is associated with healthy cognitive aging, contributing 3.3% additional variance to cognitive ability in old age after the score on the same test at age 11 was accounted for."

In the multivariable model, IQ at age 11 accounted for most of the variance in Moray House IQ test scores at age 79 (43.7% of the variance, P

They conducted a prospective cohort study looking at the relationship between BMI, cognitive function, and cognitive decline among 2,233 healthy men and women ranging in age from 32 to 62 at baseline. The cohort members were participants in the larger Aging and Health at Work study.

In 1996 and 2001 the authors collected medical, psychosocial and environmental data on the cohort, including cognitive function. The cognitive function tests consisted of word-list learning, a digit-symbol substitution test, and selective attention test.

They found that in a cross-sectional analysis, higher BMI was associated with lower cognitive score at baseline, after adjusting for age, gender, level of education, physical activity, and geographic region.

In addition, higher BMI at baseline was associated with a greater decline in all of the cognitive measures at follow-up, although the association was only significant for word-list recall, the authors found. The association between baseline BMI and cognitive decline at follow-up held up after adjusting for the confounding factors mentioned above.

In a longitudinal analysis, "whatever the test, we found a negative association between BMI at baseline and the improvement of cognitive performance, with a statistically significant linear trend," Dr. Cournot and colleagues wrote. "After adjustment for age, sex, region of residence, educational level, baseline cognitive score, and other medical or psychosocial confounders (depending on the cognitive test), the negative association between BMI and the progression in cognitive performance remained significant for word-list learning."

In contrast with other recent studies, the authors did not find evidence of an association between change in body weight and cognitive function, however, suggesting that keeping weight off from the outset, rather than taking it off later, may provide more protection against cognitive decline.

The authors noted that their study is limited by the fact that the cohort was not strictly population based, and by the lack of data on race as a possible confounding factor. French law prohibits collecting racial or ethnic data for biomedical research purposes, Dr. Cournot and colleagues noted.