Association between different domains of physical activity and osteoporotic fractures

Epidemiological studies suggest for an inverse relationship between physical activity and risk of fractures. However, it is unclear how this association varies according to the domain of life in which the activity is undertaken. In this analysis of the European Prospective Investigation of Cancer- Norfolk study, we assessed total and domain-specific physical activity using a validated questionnaire (EPAQ2) in 14,903 participants (6,514 men, mean age 62-yr). After a median follow-up of 8 years, there were 504 fractures (164 hip fractures). Metabolic equivalent measures were calculated according to frequency and duration of different activities for all participants. In multivariable Cox proportional-hazards models, moderate activities at home and for leisure were associated with reduced hip fracture risk among women (hazard ratios [HR] 0.51 and 0.55, 95%CI 0.29-0.90 and 0.30-0.93, respectively). Leisure time activities were associated with highly reduced risk of hip fracture among men (HR=0.58; p for trend<0.001) whereas activities at home increased the risk of any fracture among men (HR=1.25; p for trend=0.008). Walking for leisure/transport was associated with reduced risk of any fracture (HR=0.74, 95%CI 0.58-0.95) and hip fracture (HR=0.57, 95%CI 0.37-0.87) in both men and women. This study suggests that different domains of physical activity may relate differently to fracture risk and these relationships may vary by age and sex. The interaction observed between age and physical activity suggests for a higher impact of activity on bones in the younger ages which might not be achievable for the elderly people.