Effects of physical activity on bone mineral density in older adults: Korea National Health and Nutrition Examination Survey, 2008-2011

We compared the relationship between physical activity (PA) and bone mineral density (BMD) in men and women aged over 50 years. Only moderate-to-vigorous PA was positively associated with hip BMD in men. There was no association between PA and BMD at any site in women. Introduction Physical activity (PA) is widely recommended for osteoporosis. However, epidemiological data regarding the intensity or volume of PA required for bone health are lacking. We aimed to investigate and compare the relationship between PA and bone mineral density (BMD) in men and women. Methods This population-based cross-sectional study used data from the 4th and 5th Korea National Health and Nutrition Examination Surveys and included 2767 men and 2753 women aged > 50 years. The intensity, frequency, and duration of PA were assessed using a questionnaire, and the participants were divided into the no activity, walking-only, moderate PA, and vigorous PA groups. BMD was measured at the lumbar spine (LS), femur neck (FN), and total hip (TH) using dual-energy X-ray absorptiometry. Results Adjusted-BMDs of the hip were higher in men and women in the moderate and vigorous PA groups than those in men and women in the walking-only and no activity groups, while frequency and duration of PA were not associated with BMD at any site. The odds ratios for osteoporosis were the lowest at the FN and TH in men in the vigorous PA group (0.354, 95% confidence interval (CI) 0.139-0.901, P < 0.002, and 0.072, 95% CI 0.007-0.766, P < 0.003, respectively), while it was not significant in women. Conclusion Only moderate-to-vigorous PA was positively associated with the hip BMD in men. There was no association between PA and BMD at any site in women. It is necessary to assess the PA intensity for bone health based on the site and sex.