Epidemiology of Physical Activity and Fragility Fractures

Sammanfattning: Fragility fractures mainly affect elderly individuals and often cause long term pain, loss of function and higher mortality rates. Physical activity improves balance, increases muscle strength and bone mineral density, and may reduce the risk of fragility fractures. The aim of this thesis is to investigate the association between physical activity and fragility fractures.In Paper I the risk of hip and any fracture was investigated across levels of habitual walking/bicycling and exercise in participants from the population-based Cohort of Swedish Men (COSM) and Swedish Mammography Cohort (SMC). Individuals walking/bicycling a maximum of 20 minutes per day had a lower risk of hip and any fracture than individuals who did not walk or bicycle. The risk of hip and any fracture was gradually lower with increasing levels of exercise. In Paper II participants in the cross-country skiing race Vasaloppet were compared to non-participants from the general population, and were found to have a higher risk of any and forearm fracture but a lower risk of hip, proximal humerus and lower leg fracture. There was no difference in the risk of vertebral fracture. In Paper III, the association between physical activity and cardiovascular candidate plasma protein concentrations were analyzed in participants from the EpiHealth cohort and the Swedish Mammography Cohort Clinical. Of 184 assayed proteins, 75 associations with physical activity were discovered and 28 subsequently replicated in multivariable adjusted models. In Paper IV the COSM, SMC and the Vasaloppet cohort were combined to achieve as wide a range of physical activity as possible and a common measure of physical activity was created using generalized structural equation modeling (GSEM). Low levels of physical activity were associated with higher risk of any and hip fracture but lower risk of wrist fracture. Individuals with physical activity close to the median of the combined cohort had the lowest risk of fracture, and higher levels of physical activity was associated with a higher risk of any fracture.In conclusion, physical activity is associated with a lower risk of major fractures such as hip fractures, but may in large quantities increase the risk of wrist and any fracture. Physical activity is associated with more beneficial concentrations of 28 cardiovascular plasma proteins.