Some older people may benefit more than others from regular physical exercise. Now a study is offering some genetic clues that help explain why.

The study shows that some older people who exercise have better physical function than others and the reason may have to do with a chemical involved in blood pressure control.

"Our results reinforce the importance of exercise, but also may explain a mechanism for why it seems to benefit some individuals more than others," says Stephen Kritchevsky, PhD, professor of gerontology at Wake Forest, who led the study.

The study supports previous findings that exercising on a regular basis plays a major role in staying healthy into the later years. The researchers also show that a chemical involved in regulating blood pressure may also explain why not all seniors respond the same way to exercise.

The researchers shed new light on how an inherited gene combination present in some and absent in others may be the major factor in determining how well activity will help preserve function in individual exercisers.

The study appears in The Journal of the American Medical Association.

Functional limitations, such as limits on climbing stairs or difficulty walking, are a step toward physical disability, write the researchers. About one-third of seniors in the U.S. age 70 and older report walking limitations.

According to the researchers, these older adults have "nearly four times the risk of nursing home placement and three times the risk of death within two years."

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Exercise Is Not the Same for Everyone

Exercise has numerous benefits for heart health and physical and emotional well-being. Yet the physical response to exercise can vary greatly from person to person, and the reasons remain unclear. But genetics seem to play a role.

"Research has consistently found that exercise is associated with lower risk for physical decline," writes Kritchevsky. "But despite exercise's benefit, individual responses vary. Our current findings regarding the ACE genotype may help explain why."

The study is the first to show that a gene controlling levels of angiotensin-converting enzyme (ACE) -- a chemical involved in blood pressure control -- may be associated with better physical function in older adults. Variations of the gene have been associated with increased muscle strength, power, and endurance.

The study involved 3,075 healthy adults aged 70-79 who were followed for up to four years. About a third of the group was physically active and burned more than 1,000 calories a week in exercise, walking, and climbing stairs. The others were less active.

Physically active seniors were 33 percent less likely to report problems getting around compared with less active seniors.

Activity level was linked to variations of the ACE gene in active seniors. Inactive seniors had no such association.

Among older adults who exercised, those with ACE variations associated with improved muscle strength and endurance were less likely to develop functional limitations.

About one in four study participants had a gene variation associated with lower ACE production. These seniors did not benefit from exercise as much as the others. But they still did better than those who did not exercise.

Study results underscore the need to learn more about how the ACE system influences human health, Kritchevsky says.

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By Patti Connor, reviewed by Brunilda Nazario, MD

SOURCES: Kritchevsky, S. The Journal of the American Medical Association, Aug. 10, 2005; vol 294: pp. 691-698.