HORMONE REPLACEMENT THERAPY AND RISK OF HIP FRACTURE - POPULATION-BASED CASE-CONTROL STUDY

Objective: To determine the relative risk of hip fracture associated w ith postmenopausal hormone replacement therapy including the effect of duration and recency of treatment, the addition of progestins, route of administration, and dose. Design: Population based case-control stu dy. Setting: Six counties in Sweden. Subjects: 1327 women aged 50-81 y ears with hip fracture and 3262 randomly selected controls. Main outco me measure: Use of hormone replacement therapy. Results: Compared with women who had never used hormone replacement therapy, current users h ad an odds ratio of 0.35 (95 % confidence interval 0.24 to 0.53) for h ip fracture and former users had an odds ratio of 0.76 (0.57 to 1.01), For every year of therapy the overall risk decreased by 6% (3% to 9%) : 4%, (1% to 8%) for regimens without progestin and 11% (6% to 16%) fo r those with progestin. Last use between one and five years previously with a duration of use more than five years, was associated with all odds ratio of 0.27 (0.08 to 0.94). After five years without hormone re placement therapy the protective effect was substantially diminished ( -7% to 48%). With current use, an initiation of therapy nine or more y ears after the menopause gave equally strong reduction in risk for hip fracture as an earlier start. Oestrogen treatment with skin patches g ave similar risk estimates as oral regimens. Conclusions: Recent use o f hormone replacement therapy is required for optimum fracture protect ion, but therapy can bt started several years after the menopause. The protective effect increases with duration of use, and an oestrogen-sp aring effect is achieved when progestins are included in the regimen.