Frequent walking, but not total physical activity, is associated with increased fracture incidence: a 5-year follow-up of an Australian population-based prospective study (AusDiab).

Current public health physical activity (PA) guidelines recommend that older adults accumulate ≥ 2.5 hours per week of moderate- to vigorous-intensity PA to optimize health. The aim of this study was to examine (1) whether adults who meet the current PA guidelines are at reduced risk of fracture, (2) whether fracture risk varies by PA type/intensity and frequency, and (3) whether prolonged TV viewing, as a marker of sedentary behavior, is associated with fracture risk. This national, population-based prospective study with a 5-year follow-up included 2780 postmenopausal women and 2129 men aged 50 years or older. Incident nontraumatic clinical fractures were self-reported. Overall, 307 (6.3%) participants sustained at least one incident low-trauma fracture (women 9.3%, men 2.3%). Multivariate logistic regression, adjusting for age, body mass index (BMI), physical function, previous fracture history, smoking, and dietary calcium and serum 25-hydroxyvitamin D levels, showed that women who walked more than 3 hours per week or completed at least 6 weekly bouts of walking had a 51% and 56% increased fracture risk, respectively, compared with women who did no walking [odds ratio (OR) time = 1.51, 95% confidence interval (CI) 1.01-2.24; OR frequency = 1.56, 95% CI 1.07-2.27]. However, total and moderate to vigorous PA time and the accumulation of 2.5 hours per week or more of PA and TV viewing time were not associated with incident fractures. In men, there also was an increased fracture risk for those who walked more than 3 hours per week (OR = 2.30, 95% CI 1.06-4.97) compared with those who reported no walking. In conclusion, older adults who adhered to the current PA guidelines were not protected against fragility fractures, but more frequent walking was associated with an increased fracture risk.
(Copyright © 2011 American Society for Bone and Mineral Research.)