Physical activity and 10-year incidence of self-reported vertebral fractures in Japanese women: the Japan Public Health Center-based Prospective Study.

UNLABELLED: This study assessed the effects of physical activity on a 10-year incidence of self-reported vertebral fractures in adult women of a large Japanese cohort. Medium levels of strenuous activity and long-duration sedentary activity were associated with a lower incidence of vertebral fractures; association patterns appear to be different from hip fractures. INTRODUCTION: Physical activity helps prevent hip fracture, but little is known about the longitudinal association between physical activity and vertebral fractures. The purpose of this study was to evaluate the effects of physical activity on the 10-year incidence of symptomatic vertebral fractures using data from the Japan Public Health Center-based Prospective Study. METHODS: Baseline studies were conducted in 1993-1994, and the follow-up study was conducted 10 years later. We analyzed 23,757 women aged 40-69 years. At baseline, physical activity was assessed as a predictor by using a questionnaire. Subjects were asked to report vertebral fractures that occurred during the 10-year follow-up period. Relative risks (RRs) adjusted for confounders were estimated by multiple logistic regression analysis. RESULTS: The 10-year cumulative incidence of vertebral fractures was 0.67%. Those who engaged in strenuous physical activity of <1 h/day had a significantly lower incidence of vertebral fractures than those who did not engage in such activity (RR = 0.52, 95% CI 0.28-0.97), while those engaged in such activity ≥1 h/day did not (RR = 0.82, 95% CI 0.58-1.14). Long-duration sedentary activity was associated with a low incidence of vertebral fractures (P for trend = 0.0002), but the frequencies of sports activities and metabolic equivalents were not (P for trend = 0.0729 and 0.4341, respectively). CONCLUSIONS: Strenuous activity and sedentary activity are associated with the incidence of vertebral fractures, although the association may not be linear. The pattern of association between physical activity and vertebral fractures appears to be different from that of hip fractures.