How Safe Is Exercise? A Cross-Sectional Analysis Between Mid-Life Physical Activity And Fractures In UK Biobank

Objective: To examine associations between volume and intensity of leisure time physical activity (LTPA) and fracture risk during midlife and determine whether adherence to World Health Organisation (WHO) physical activity recommendations was associated with fracture risk. Methods: Cross-sectional analysis of UK Biobank participants aged 40 to 65 years using self-reported physical activity and fracture data. LTPA volume (LTPAV) was derived from walking, moderate and vigorous activity. Participants were categorised into LTPAV quintiles and by adherence to WHO physical activity recommendations. Multivariable logistic regression examined associations with self-reported fracture within the previous five years, with sex stratified analyses. Results: Among 322,749 participants, 53% were female with a mean age of 47 years. Fracture risk increased with higher LTPAV, although the association was non-linear and varied by age and sex. The strongest associations were in the highest quintile among men and women aged 40 to 49 years (OR 1.81, 95% CI 1.64 to 1.99 and OR 1.42, 95% CI 1.28 to 1.58 respectively). In mutually adjusted models, vigorous activity demonstrated the strongest independent association with fracture risk. Meeting WHO physical activity recommendations, without exceeding them, was not associated with increased fracture risk. Conclusions: Higher fracture risk was observed in individuals undertaking higher volumes of leisure-time physical activity, with the association largely driven by vigorous-intensity activity. The association was strongest in adults aged 40 to 49 years and in men. Physical activity consistent with current WHO recommendations was not associated with increased fracture risk, supporting continued promotion of physical activity during midlife.