Observational studies on hormone replacement therapy (HRT) have shown cardioprotective effects that have not been replicated in randomized controlled trials, perhaps due to unaccounted confounding by socioeconomic factors. To resolve this discrepancy, we examined the association between socioeconomic status (SES) and HRT use in a large population of Danish postmenopausal women.
We conducted a register-based cross-sectional study based on all women aged 40 or more with a permanent address in the North Jutland County, Denmark on 1 January 1999 (n = 122 584). The women were classified according to SES through the Prevention Registry at Statistics Denmark. Through the Pharmaco-epidemiological Prescription Database, we identified all reimbursed HRT prescriptions in North Jutland County for women aged 40 or more in the study population during 1999. We calculated 1-year prevalence proportions of HRT use for all socioeconomic groups. Between-group comparisons were made by log-risk analysis with adjustment for age.
The estimated overall user-prevalence of HRT in 1999 among Danish postmenopausal women was 14.9%[95% confidence interval (CI) 14.7-15.1]. No substantial socioeconomic gradient was found in the study. The adjusted relative prevalence proportions (RPPs) varied between 0.90 and 1.14 among the different groups when using salaried employees, basic level, as the reference group.
Our findings suggest that recent observational studies on the use of hormone replacement therapy among women in Denmark may not have suffered from strong confounding by socioeconomic status.