- The Washington Times - Tuesday, July 11, 2006

Seniors who expend more energy through daily activity, including such simple tasks as cooking, vacuuming, washing dishes, gardening or climbing stairs, have a lower death rate than those who are less active, a federal study has found.

Researchers with the National Institute on Aging (NIA) followed 302 healthy “high-functioning” non-institutionalized adults, ages 70 to 82, for an average of slightly more than six years. Fifty-five participants, or 18.2 percent, died during the follow-up period.

“Simply expending energy through any activity may influence survival in older adults,” the authors concluded in their report, published in today’s issue of the Journal of the American Medical Association (JAMA).

In fact, the study showed that seniors in the highest third in terms of levels of activity had a 69 percent lower risk of death than those in the lowest third.

Todd M. Manini, a research scientist at NIA and the study’s lead author, said, “We’re saying that higher energy use is associated with a lower risk of mortality, and this energy can come from many more sources than most people might think.”

Just standing “burns more energy than sitting,” Mr. Manini said. He noted that energy is burned even by fidgeting in a seat, “but it is a lot less than would be achieved through a 10-minute walk.”

Previous observational studies have shown that older adults who report low physical activity levels are at a higher risk of death than those who report moderate or high levels of activities.

But the NIA researchers said those findings were based on questionnaires asking about physical activity levels. In such self-reporting, they said, information may not be recalled accurately, and many types of daily activity may be overlooked.

What’s more, they said, self-reported physical activity does not provide data on “absolute amounts of activity” and so cannot be used “to determine whether higher levels of activity-induced energy expenditures confer survival advantages.”

For the study in JAMA, Mr. Manini and his team used an objective but costly method of measuring a person’s activity. They measured energy expenditure over a two-week period by having participants drink water labeled with certain isotopes of hydrogen and oxygen. The technology cost between $500 and $1,000 per trial participant.

“When ingested, hydrogen is eliminated as water, and oxygen is eliminated as water and carbon dioxide. The excess disappearance rate of [oxygen] relative to [hydrogen] is a direct measure of the carbon dioxide production rate, a direct measure of total energy expenditures,” the report’s authors wrote.

In an accompanying editorial in JAMA, Steven N. Blair of the Cooper Institute in Dallas and William L. Haskell of the Stanford University School of Medicine wrote: “Higher levels of activity energy expenditure appear to be protective. Public health officials should consider how these results can be translated into recommendations for individuals.”

Mr. Blair and Mr. Haskell say the NIA researchers’ conclusion that “simply expending energy through any activity may influence survival in older adults is provocative” and “would have major implications for physical activity recommendations … if documented by further research.”

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