Post-menopausal oestrogens protect against fractures of hip and distal radius. A case-control study.

To assess the efficacy of oestrogens in preventing the common major limb fractures of postmenopausal women, retrospective case-control research was used for a new purpose--to explore beneficial rather than adverse effect of treatment. Postmenopausal women admitted with fractures of the hip or distal radius and matched women admitted to the orthopaedic service for other reasons were surveyed. The "risk" of the non-oestrogen users, was estimated by inverting the customary odds ratio to calculate protection in terms of numbers of (exposed controls x non-exposed cases) divided by (exposed cases x non-exposed controls). Medical-record data for oestrogen usage in 157 matched case-control pairs gave an odds ratio for "protection" of 1.5 (10 x 150 divided by 7 x 147). If "exposure" was defined as starting oestrogens within 5 years of the menopause, this ratio rose to 2.6 (10x153 divided by 4x147). With oestrogen usage ascertained from standardised interviews of 80 case-control pairs, the ratio was 3.0 (20x72 divided by 8x60) (p=0.01), and rose to 3.8 (16x75 divided by 5x64) (p=0.01) for oestrogen "exposure" that began within five years of menopause. When lateral chest X-rays were blindly reviewed, the prevalence of oesteoporosis was 32% in the fracture cases and 15% in controls (p less than 0.01). The results add epidemiological evidence for the belief that exogenous oestrogens protect against postmenopausal osteoporosis.