The epidemiology of hip fractures in the elderly

This thesis addresses three issues which are fundamental to the design of preventive strategies for hip fractures in the elderly: the independent contribution of osteoporosis to the risk of hip fracture, the roles of low dietary calcium intake and physical inactivity as risk factors for hip fracture, and the geographic variation in hip fracture incidence within England and Wales. Femoral neck bone mass was measured in 708 elderly people who had fallen and injured a hip. Bone mass was lower in those who had sustained a hip fracture than in those who did not. There was a steep increase in the risk of fracture with reduced bone mass at younger ages. At older ages, the risk gradient was less steep. The results suggest that osteoporosis contributes to the risk of hip fracture in the elderly independently of the risk of falling. Other age-related factors become increasingly important above the age of around 75 years. A case-control comparison between 300 elderly men and women with hip fractures and 600 age and sex matched community controls showed that physical inactivity and reduced grip strength were associated with statistically significant (p< 0.01) increases in fracture risk. In women, dietary calcium intake did not influence the risk of fracture. Men with daily calcium intakes above one gram had lower risks. Examination of death certification from hip fracture in England and Wales showed major inaccuracies which limit the usefulness of mortality rates as indices of the incidence of the condition. These studies suggest that the risk of hip fracture in the elderly depends upon an interaction between osteoporosis, the risk of falling and other age-related factors. Physical inactivity and concomitatnt muscle weakness are important individual risk factors for hip fracture. They may influence fracture risk through an effect on bone mass, the risk of falling or both of these. The results support the maintenance of activity and muscle strength in the elderly. Such a strategy requires prospective evaluation.