The effect of postmenopausal estrogen therapy on the risk of non-insulin-dependent diabetes mellitus

Objectives. This study examined the effect of postmenopausal estrogen replacement therapy on the incidence of non-insulin-dependent diabetes in women. Methods. Postmenopausal women aged 50 through 70 years (n = 848) without diagnosed diabetes at baseline were followed for 10 to 15 years for incident diabetes. Results. Over the average 11.5 year follow-up, there were 105 new cases of diabetes. The age-adjusted relative-risk for development of diabetes was nonsignificantly fewer for women with continuous estrogen replacement therapy use than for never users. After adjustment for major covariates, a nonsignificant linear trend with increasing duration of estrogen replacement therapy was reversed. Conclusions. This study suggests that previous results showing a reduced risk of diabetes in women using estrogen may have been due to selection bias regarding who is prescribed estrogen, confounding factors, or differential diagnostic efforts.