Fracture reducing potential of hormone replacement therapy on a population level

ObjectivesTo study the fracture reducing potential of hormone replacement therapy (HRT) at a population level, the effect of age on the fracture reducing potential of HRT, and to examine whether socio-economic factors confound the effects of HRT on fracture risk.Subjects and methodsCase–control study. All women who sustained any fracture during the year 2000 in Denmark served as cases (n = 64,548). For each case, three age-matched controls were randomly drawn from the background population (n = 193,641). The main exposure was the average daily dose of HRT (expressed as defined daily doses DDD/day). Adjustments were made for co-morbidity, socio-economic factors, and prior fracture.ResultsA fracture risk reduction was seen in women aged ≥50 years using ≥0.3 DDD/day. The risk reduction for any fracture was larger in women aged ≥60 years (0.3–0.99 DDD/day: odds ratio (OR) = 0.77, 95% confidence intervals (CI): 0.73–0.82, ≥1 DDD/day: OR = 0.61, 95% CI: 0.56–0.67) than in women aged 50–59 years (0.3–0.99 DDD/day: OR = 0.92, 95% CI: 0.85–0.99, ≥1 DDD/day: OR = 0.77, 95% CI: 0.70–0.84). Larger risk reductions were seen for Colles’ fractures (age 50–59 years: OR = 0.64 for 0.3–0.99 DDD/day, and OR = 0.57 for ≥1 DDD/day, age ≥60 years: OR = 0.52 for 0.3–0.99 DDD/day, and OR = 0.40 for ≥1 DDD/day). Adjustment only changed the estimates little. No difference between oral and dermal preparations could be found.ConclusionsHormonal replacement therapy possesses a fracture-reducing potential at population level even at dosages lower than usually recommended. The risk reduction was larger with advancing age for any fracture and Colles’ fractures.