DIET AND HIP FRACTURE RISK - A CASE-CONTROL STUDY

Background. The role of diet as a risk factor for osteoporotic fractur es is unclear. Earlier studies have yielded conflicting results. Metho ds. In two counties in central Sweden we investigated the association between dietary intake and the risk of proximal femoral fractures in a case-control study nested in a cohort. Women born in 1914-1948 were a sked to fill out a food frequency questionnaire when invited to attend for mammographic screening between the years 1987 and 1990. More than 65 000 women completed the questionnaire. Those who had participated in the enquiry and subsequently sustained a first hip fracture were de fined as cases. For every case, four individually matched controls, by age and county of residence, were selected from the cohort. A second questionnaire concerning confounding factors was mailed to controls an d cases. In all, 247 cases and 893 controls could finally be included. Monthly intake of foods and daily intake of nutrients were calculated . Results. When highest quartile of intake was compared to lowest, int akes of iron (adjusted odds ratio [OR] of 3.3, 95% confidence interval [CI] : 1.6-6.9), magnesium (adjusted OR = 2.7, 95% CI : 1.3-6.0) and vitamin C (adjusted OR = 1.9, 95% CI : 1.2-3.1) were found to be indep endent risk factors for hip fracture. High calcium intake did not prot ect against hip fracture. Smoking, low physical activity in leisure ti me, low body mass index, earlier fracture of the distal forearm and di abetes were all risk factors while postmenopausal hormone replacement therapy protected against hip fracture. Discussion. This large study i ndicates new dietary risk factors for hip fracture. The association be tween high dietary intake of iron, magnesium and vitamin C and risk of hip fracture has not been reported previously. Further clinical and e xperimental studies are needed to confirm these findings and to invest igate their mechanism of action.