Objectively Measured Physical Activity Is Associated with Vertebral Size in Midlife

Background Vertebral fractures reduce the quality of life and are a major burden to the health care sector. Small vertebral size is associated with increased vertebral fracture risk. Previous studies have investigated the relationship between physical activity (PA) and vertebral size, but their results seem somewhat contradictory. In this population-based birth cohort study, we aimed to evaluate the relationship between objectively measured PA and vertebral size. Methods The study population consisted of 1202 cohort participants who underwent PA and vertebral size measurements at the age of 46 to 48 yr. Moderate-to-vigorous PA (MVPA, >= 3.5 METs) was measured by a wrist-worn accelerometer (Polar Active; Polar Electro, Finland) for 14 d. The vertebral axial cross-sectional area (CSA) of the L4 vertebra was measured and calculated from lumbar magnetic resonance imaging scans at 46 to 48 yr. We analyzed the association between the daily amount of MVPA (min center dot d(-1)) and vertebral CSA using multivariable linear regression analysis. Results The daily amount of MVPA was significantly and positively associated with CSA in both sexes. For every minute per day of MVPA, men had 0.71 mm(2) (95% confidence interval, 0.36-1.06) and women 0.90 mm(2) (95% confidence interval, 0.58-1.21) larger CSA. Conclusions Physical activity of at least moderate intensity is positively associated with vertebral size and may thus prevent future vertebral fractures.