In the United States, one in every three adults 65 years old or older falls each year, with hip fractures resulting in the greatest number of deaths and most serious health problems. Women account for 80 percent of the 300,000 hip fractures that occur annually. A study, which included investigators from the Harvard School of Public Health, showed that women who walked at least four hours per week had approximately a 40 percent reduction in the risk of hip fracture, compared with women who were mostly sedentary. Higher-impact exercise provided greater protection. Exercise equivalent to about three hours of jogging per week reduced risk of hip fracture by approximately 50 percent. These results were based on the analysis of questionnaires beginning in 1986 from more than 61,000 postmenopausal women, ranging in age from 40 to 77 years, participating in the Brigham and Women’s Hospital-based Nurses’ Health Study.