Past and current physical activity levels and the risk of fracture in a population based study with 25 years follow-up

Norway has the highest fracture incidence in the world, and data from Oslo indicate increasing incidence in both sexes to the end of 1990. Physical activity stimulate bone formation during growth and maintain bone strength and reduce bone loss in adulthoo d and old age. Physical activity throughout life might therefore have substantial effect on bone health. Little is however known about how physical activity at younger age influence risk of fracture in older age and very few studies have addressed fractur e risk in men. The aim of this project is therefore to examine the relationship between physical activity at younger age, during middle age, and risk of non-vertebral fractures occuring at older age in both women and men. The project will utilise data a lready collected in the longitudinal population based Tromsø study, which started in 1974. From the 1979/80 survey women have also attended, and after Tromsø V in 2001/02, 38202 persons have participated in at least one of five surveys, 12605 in three or more surveys. Data on physical activity is collected in all surveys, together with other lifestyle information. Bone mass was measured at the forearn in Tromsø IV 1994/95 and Tromsø V 2001/02, at the hip and total body in Tromsø V. Fractures are registere d in the cohort from 1988 to 2005. In addition, more data will be collected in Tromsø VI, starting in October 2007. We apply for fundings for technical assistant to collect new data in Tromsø VI and one PHD student, who shall over the project period : 1. Describe secular trends in physical activity levels in leisure time over the last three decades. 2. Examine the association between physical activity levels at younger age and fracture risk in old age? 3. Examine the association between changing physical activity levels and fracture risk later in life? 4. Examine the association between physical activity levels in younger age and BMD levels in older age.