Hormone replacement therapy, other reproductive variables and symptomatic hip osteoarthritis in elderly white women: a case-control study.

Background: Recent epidemiological studies suggest that post-menopausal hormone replacement therapy might reduce the risk of hip osteoarthritis (OA) in women. However, the association of the disorder with other reproductive variables is controversial. We addressed this issue in a population-based case control study among 413 female cases and 413 age- and sex-matched controls.

Methods: A total of 413 women listed for hip replacement because of primary OA over an 18 month period were compared with an equal number of controls selected from the general population and individually matched for age and general practice. Information about reproductive variables was obtained by questionnaire administered at interview.

Results: The risk of hip OA was significantly elevated among women who had had an oophorectomy (OR = 1.9, 95% CI 1.0-3.7). After adjustment for body mass index, the presence of Heberden's nodes, previous hip injury and past leisure sporting activity (all independent risk factors for hip OA), and for other reproductive variables, there was a non-significant, protective effect of long-term hormone replacement therapy, such that > or =5 yr of use was associated with a 40% reduction in risk (OR = 0.6, 95% CI 0.2-1.8). Paradoxically, short-term HRT use (up to 5 yr duration) was associated with an excess risk of hip OA (OR = 1.7, 95% CI 0.9-3.3). There was no association between the risk of hip OA and use of oral contraceptives, parity or hysterectomy.

Conclusions: These data are consistent with previous studies suggesting a protective effect of long-term hormone replacement therapy on the risk of hip OA. By contrast, an elevation of risk in short-term users was demonstrated. Our results also suggest that risk is increased among women who have undergone unilateral or bilateral oophorectomy. Studies are required to investigate the mechanisms underlying these associations.