Ability to complete quarter-mile walk a powerful predictor of health outcomes in elderly

May 2 2006

Walking fitness makes a significant difference in predicting the likelihood of future disability in the elderly, according to a study published today in the Journal of the American Medical Association.

Researchers at the University of Pittsburgh Graduate School of Public Health (GSPH) and their collaborators found that the ability to walk 400-meters, or about a quarter mile, was an important determinant not only of whether elderly participants would be alive six years later but also how much illness and disability they would experience within that time frame.

"The ability to complete this walk was a powerful predictor of health outcomes. In fact, we found that the people who could not complete the walk were at an extremely high risk of later disability and death," said lead author, Anne B. Newman, M.D., M.P.H., professor of epidemiology at GSPH and professor of medicine in the department of medicine, University of Pittsburgh School of Medicine.

Dr. Newman and her co-workers, collaborating with researchers at five other institutions, asked a group of almost 2,700 community-dwelling white and African-American men and women aged 70 to 79 to complete, as quickly as they could--without running--and at a consistent pace, ten 40-meter laps in a corridor. All of the participants previously had reported no difficulty walking a quarter of a mile, climbing one flight of stairs without resting or performing basic activities of daily living. Participants were excluded from attempting the walk if they had an abnormal electrocardiogram, elevated blood pressure or resting heart rate or recently had a procedure for, or symptoms of, heart disease. Those participants who qualified for the quarter-mile walk were told to stop if they experienced any signs of fatigue or persistent rapid heart rate.

Of the 2,680 elderly people eligible for the test, 2,324 (86 percent) completed the full 400-meters, while 356 (13 percent) did not complete the test. The investigators followed the medical histories of all participants--whether they completed the walk or not--for about six years.

Among those excluded from or who stopped the walk, death rates were significantly higher six years later than those who completed the walk. In addition, of the more than 2,200 participants who did not have a clinical diagnosis of cardiovascular disease at the time of the test, those who did not complete the walk had significantly more heart-related incidents six years later compared to those who did. The former group also had a significantly higher risk of persistent limitations in their mobility and related disabilities than did those who completed the full 400-meters.

"A significant portion of people in the study could not complete the walk, even though they believed they were in fairly good health. Moreover, there was a big gap in health outcomes between people who could complete the longer walk and people who could not, with the latter being at an extremely high risk of becoming disabled or dying. What was really surprising is that these people were not aware of how limited they actually were," explained Dr. Newman, who also is a collaborator with the University of Pittsburgh Institute on Aging.

Even among those who completed the walk, those in the slowest 25 percent for walk time had a three- to four-fold higher risk of death than those in the fastest 25 percent for walk time. Those in the slowest 25 percent of walk time also had a higher risk of cardiovascular disease-related complications and limitation in their mobility and mobility-related disabilities than those in the fastest 25 percent.

Based on these results, Dr. Newman and her collaborators believe the 400-meter long-distance corridor walk offers a relatively simple but powerful way to discriminate levels of function, particularly among the elderly with normal performances on lower extremity tests or on short walking tests. More importantly, it can point out who needs intervention.

"Our study found that many people who performed well on lower extremity tests or short walking tests did not perform well on the 400-meter walking test. Although quite simple, the 400-meter walk appears to be a highly accurate way to predict whether or not someone may be experiencing early problems and needs an immediate referral into an intervention program to help them increase their activity and physical stamina," she explained.

Unfortunately, many communities have structural barriers that prevent the elderly from maintaining physical fitness, so these findings have public policy as well as public health implications, said the authors. According to Dr. Newman, it is difficult for many older people to find safe places to walk, and many can't afford indoor exercise equipment, such as treadmills. As a result, the elderly tend to become more and more sedentary as they grow older, setting them up for major problems as they age.

"Individuals who remain physically active into their 70s have a big advantage in their 80s in terms of living longer and reducing their risk of cardiovascular disease and disability. So, we really need to focus on developing programs in the community that will help the elderly stay active and healthier longer," she said.

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