Researchers from Brigham and Women's Hospital mined data from a large study, collecting information on the activity and sitting habits of almost 36,000 men over 24 years.
Their study relied on answers on questionnaires that the men filled out every two years about how vigorously they walked -- at an easy, average or brisk pace -- as well as their time spent sitting and performing other activities, including tennis, lap swimming and outdoor work.
During the 24-year follow-up period, 546 hip fractures were reported, not including fractures due to cancer or a traumatic event such as a fall during skiing or a car accident. Eighty-five percent of the fractures involved "low-trauma" events such as slipping, tripping or falling from a chair.
The results suggest that the more a man walked, and the more vigorously he walked, the lower his risk for hip fracture as he aged, the authors reported. For men whose primary activity was walking, doing so at least four hours a week was associated with a significant drop in hip fractures -- a 43 percent lower risk than walking less than one hour a week.
"It's well known that physical activity helps to prevent hip fractures, that it helps to build bone and muscle tone. It can help with balance, too," said study author Diane Feskanich, an assistant professor at Harvard Medical School and an associate epidemiologist in the department of medicine at Brigham and Women's Hospital in Boston.
"One thing we're pointing out here is that it doesn't necessarily have to be strenuous activity," Feskanich said. "A lot of studies have focused on the benefits of strenuous activity, but we found walking alone helped to prevent hip fractures, and when you come down to it, older people are often more comfortable with walking."
Because of different fracture risks, men of African American or Asian ancestry were not included in the study, which was published online Feb. 13 in the American Journal of Public Health.
Dr. Neil Roth, an attending orthopedic surgeon at Lenox Hill Hospital in New York City, and a specialist in sports medicine, said bones are not static organs -- they're fluid. "The cells are constantly breaking down bone and making new bone," he said.
The way to keep bones healthy and strong is by increasing stress on the bone through activity, but not to overdo it, either, he said. "You want to stay below the threshold that becomes dangerous but also push it to the point that builds bone mass -- find the sweet spot -- but that will be different for everybody," Roth said.
An obese 75-year-old man will not be able to do the same activity as a 65-year-old who is in good shape, Roth noted. He also said that while walking may help with some balance and cardiovascular issues, it may not fully address those and other health issues.
"Balance in the elderly is a very complicated situation. If someone has better balance, they're much less likely to fall and the majority of hip fractures occur from a fall. But all sorts of things can affect balance in elderly -- inner ear issues, or vertigo," he said, as well as poor eyesight and medications. But he said a walker or cane can help people maintain a healthy walking routine.
Roth advises that men get cleared by their internist or cardiologist, though, before starting an exercise routine, and that they listen to their bodies during physical activity, especially if they experience bone pain.
Feskanich said she and colleagues performed a similar earlier study in women and the results almost mirrored this study: "We found almost the exact same results in women and men, about the same numbers."
She said the new findings may boost recommendations for more walking. "But a good clinician is already telling their older patients to be walking and active," she added.
Visit the U.S. National Institute of Arthritis and Musculoskeletal and Skin Diseases to learn more about exercise and bone health.