August 19, 2008 - By Erin Digitale
Regular running slows the effects of aging, according to a new study from the School of Medicine that tracked 500 older runners for more than 20 years. Elderly runners have fewer disabilities, a longer span of active life and are half as likely as nonrunners to die early deaths, the research found.
'The study has a very pro-exercise message,' said James Fries, MD, professor of medicine emeritus and the study's senior author. 'If you had to pick one thing to make people healthier as they age, it would be aerobic exercise.' The findings appear in the Aug. 11 issue of the Archives of Internal Medicine.
When Fries and his team began the study in 1984, many scientists thought vigorous exercise would do older folks more harm than good. Some feared the long-term effect would be floods of orthopedic injuries, with older runners hobbled. Fries had a different hypothesis: regular exercise would extend high-quality, disability-free life. Keeping the body moving, he speculated, might not extend longevity, but it would compress the period at the end of life when people couldn't do daily tasks on their own. The idea became known as the 'compression of morbidity' theory.
Fries' team began tracking 538 runners over age 50, and a similar group of nonrunners. The subjects, now in their 70s and 80s, answered yearly questionnaires on their ability to do tasks such as walking, dressing, getting out of a chair and gripping objects. The team used national death records to find who died and why. Nineteen years into the study, 34 percent of nonrunners had died compared with 15 percent of runners.
At the beginning of the study, the runners ran an average of about four hours a week. After 21 years, their running time declined to an average of 76 minutes a week, but they were still seeing health benefits from running.
Both study groups became more disabled after 21 years of aging, but for runners the onset of disability was later.
'Runners' initial disability was 16 years later than nonrunners,'' Fries said. 'By and large, the runners have stayed healthy.'
Not only did running delay disability, but the gap between runners' and nonrunners' abilities got bigger with time.
'We did not expect this,' Fries said. 'The health benefits of exercise are greater than we thought.'
Fries was surprised the gap between runners and nonrunners continued to widen even as they entered their 80s. The effect was probably due to runners' greater lean body mass and healthier habits in general. 'We don't think this effect can go on forever,' Fries added. 'We know that deaths come one to a customer. Eventually we will have a 100 percent mortality rate in both groups.'
But so far, the effect of running on delaying death has been more dramatic than scientists expected. Not surprisingly, running slowed cardiovascular deaths. However, it was also associated with fewer early deaths from cancer, neurological disease, infections and other causes.
The dire injury predictions other scientists made for runners have fallen flat. Fries and colleagues published a study in the August issue of the American Journal of Preventive Medicine that showed running was not linked with higher rates of osteoarthritis in older runners. Runners also did not require more total knee replacements, Fries said.
Fries, 69, takes his own advice: he's a runner, mountaineer and outdoor adventurer. Hanging on his office wall is a photo he joked was 'me, running around the world in two minutes.' It shows him amid blue sky and white ice, making a tiny lap around the North Pole.
Fries collaborated with Stanford colleagues Eliza Chakravarty, MD, MS, an assistant professor of medicine; Helen Hubert, PhD, a researcher now retired from Stanford, and Vijaya Lingala, PhD, a research software developer.
The research was supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases and by the National Institute on Aging.
Erin Digitale is a science-writing intern in the Office of Communication & Public Affairs.
Stanford Medicine integrates research, medical education and health care at its three institutions - Stanford School of Medicine, Stanford Health Care, and Stanford Children's Health. For more information, please visit the Office of Communications website at http://mednews.stanford.edu.