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 hor mone replacement therapy might reduce the risk of hip osteoarthritis (OA) i n women. However, the association of the disorder with other reproductive v ariables is controversial. We addressed this issue in a population-based ca se-control study among 413 female cases and 413 age- and sex-matched contro ls. 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 g eneral practice. Information about reproductive variables was obtained by q uestionnaire 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 m ass index, the presence of Heberden's nodes, previous hip injury and past l eisure sporting activity (all independent risk factors for hip GA), and for other reproductive variables, there was a non-significant, protective effe ct of long-term hormone replacement therapy, such that greater than or equa l to 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 a ssociated with an excess risk of hip OA (OR = 1.7, 95% CI 0.9-3.3). There w as 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 p rotective effect of long-term hormone replacement therapy on the risk of hi p OA. By contrast, an elevation of risk in short-term users was demonstrate d. Our results also suggest that risk is increased among women who have und ergone unilateral or bilateral oophorectomy. Studies are required to invest igate the mechanisms underlying these associations.