Diseases in the hip - Exploring risk for fracture and osteoarhritis

Abstract: Objective: Hip fracture is the most serious condition linked to low bone mass or osteoporosis, and Sweden has one of the highest incidences in the world. The proportion of elderly is increasing in the Swedish population and in the world, and with increased age comes increased incidence for both fragility fracture and osteoarthritis. We therefore aimed to expand knowledge about risk factors for hip fracture and osteoarthritis. Methods: All studies in this thesis were based on the entire Swedish population born between 1902 and 1952 (n=4,546,820). In Paper I we focused on married couples (n=904,451), in Paper II on farmers (n=97,136), in Paper III on women and men with total knee replacement (n=39,291), and in Paper IV we focused on widows and widowers (n=558,950). Statistics concerning risk factors were calculated with Poisson regression models. Results: The risk of hip fracture was higher after hip fracture in a spouse, after total knee replacement, and after the death of a spouse, compared to non-exposed. Women and men combined had an increased risk for trochanteric fracture after total knee replacement. Farming seemed to decrease the risk for hip fracture in men only, but increased the risk of total hip replacement due to primary osteoarthritis in both female and male farmers. Conclusion: A previous hip fracture in spouse increased the risk for hip fracture in women and men, most likely due to choosing a similar partner to oneself, along with shared lifestyle and environment. Farming seemed to protect against hip fracture in men but not in women, but increased the risk of total hip replacement. The reason for these results might be the high physical activity level and heavy loading, but why women did not have a lower risk for hip fracture is unknown. Both women and men had a higher risk for hip fracture after total knee replacement, which might be explained by reduced mobility, pain, low bone mineral density, and changed kinematics. The risk for hip fracture also increased after the death of a spouse, which might be explained by the stress caused by grief and perhaps also from the stress caused by taking care of a dying spouse.