The epidemiology of hip fractures among elderly women in Nord-Trøndelag: HUNT 1995-97 The Nord-Trøndelag Health Study
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Hip fractures constitute a large public health problem. Norway is among the countries with the highest incidence of such fractures. Women, in particular elderly women, are at higher risk than men. Preventing hip fractures presupposes broad knowledge about risk factors which may or may not be related to osteoporosis, magnitude of the problem, and long term consequences. Through this work we wanted to make a contribution to the knowledge about incidence, seasonal variation and mortality related to hip-fractures among elderly women in Nord- Trøndelag. Additionally, we wanted to evaluate the effect of dairy products on bone mass density and fracture risk. Data used in this thesis are based on information from the osteoporosis and fracture study in the second health survey in the county of Nord Trøndelag (HUNT 2). A total of 8,824 women aged 65 or more when participating in HUNT 2 have been followed prospectively. Of these, 5,661 had their forearm bone mineral density (BMD) measured at baseline. From the two hospitals in the county, hip fractures were registered until 31.12.2004. The overall hip fracture incidence rate between 1997 and 2004 was 13.1 per 1000 person years (95 % CI 12.2-14.1). This is lower than rates reported from other parts of Norway. The fracture incidence remained stable during the 9 years of follow up. We also found seasonal variation, with higher fracture rates during the winter months. Women who sustained a hip fracture had excess mortality at three months after hip fracture compared with women without fracture (HR 6.5, 95 % CI 4.2 – 9.6). The excess mortality persisted for at least five years after the event. Excess mortality associated with hip fractures did not seem to be explained by pre-fracture conditions (diabetes, stroke, cancer, angina,myocardial infarction), body mass index (BMI), smoking habits and estrogen use. We found no association between BMD and increased risk of mortality. Dairy food intake was positively associated with BMD, and displayed a dose-response pattern. However, we found no dose response association between amounts of dairy products consumed and hip fracture risk. The few women in the study (1.9 %), who did not consume dairy products daily, did not have increased fracture risk. In conclusion, the fracture rates remained stable during the follow-up period, and a higher fracture rate was observed in the winter. Excess mortality after hip fractures persisted for at least five years after the event, and could not be explained by pre-fracture morbidity. We found no dose-response association between amount of dairy products consumed and risk of hip fractures.
UtgiverNorges teknisk-naturvitenskapelige universitet, Det medisinske fakultet, Institutt for samfunnsmedisin
SerieDoktoravhandlinger ved NTNU, 1503-8181; 2011:130
Dissertations at the Faculty of Medicine, 0805-7680; 507