Association between Bone Quality and Physical Activity in Community-Dwelling Older Adults

Bone quality is an essential factor determining bone strength. However, the relationship between physical activity (PA) and bone quality remains unclear. This study aimed to ascertain the relationship between bone quality and PA using a cortical bone quantitative ultrasound device that measures components of bone quality. In this cross-sectional study, bone quality was assessed in community-dwelling older adults by measuring the cortical speed of sound (cSOS) at the mid-tibia using a quantitative ultrasound device. Using a wrist-worn accelerometer, we calculated the daily duration of moderate-to-vigorous physical activity (MVPA) and light physical activity (LPA) based on estimated METs from the accelerometer data, without differentiating between types of activities. A multiple regression analysis was performed to examine the association between PA and the cSOS. The participants' physical activity averaged 42.0 min/day for MVPA and 483.6 min/day for LPA. No significant association was observed between PA and bone quality in either men or women in the crude models. Furthermore, PA was not significantly correlated with the cSOS in the models adjusted for age, body mass index, nutrient intake, number of medications, and kidney disease. This study was a cross-sectional study which focused on the association between bone quality in older adults and their current amount of PA. The cSOS, as a measure of bone quality, was not associated with PA in men or women. Higher amounts of daily PA, as estimated from metabolic equivalents with an accelerometer, may not necessarily maintain or improve bone quality in older adults. This study does not rule out the potential for a positive association between PA levels or types and bone quality in younger or middle-aged individuals. It was specifically targeted at older adults, and its findings should not be generalized to younger populations. Further longitudinal studies are required to better understand the relationship between PA and bone quality.