It is too early to recommend hormone replacement therapy for the prevention of cardiovascular disease, Scandinavian researchers say this week. They report a study in which women who used HRT were at lower risk of cardiovascular disease before starting treatment than women who did not use HRT.
The researchers, from Gothenburg university, studied 1,201 women over a 24 year period; 15 per cent of women used HRT at some point during the study period. Before the start of their treatment, these women had significantly lower blood pressure, were less obese and belonged to a higher social group than women who did not use HRT.
Several studies in recent years have reported a beneficial effect of HRT on cardiovascular disease, with some indicating a 50 per cent risk reduction. Critics of these studies have, however, suggested that women using HRT represent a special subgroup of the population. The Scandinavian authors suggest that reported beneficial effects are likely to have been confounded by pre-existing differences in the health of users and non-users. "Our findings are consistent with the hypothesis that there has been a self selection of more healthy women for HRT." A large proportion of the "beneficial" effects of HRT may be an artefact of selection, the researchers say. They suggest that randomised, controlled studies are needed before HRT can be recommended for prevention of cardiovascular disease (British Medical Journal 1999;319:890).