Aims: To describe changes in the prevalence of hormone replacement therapy (HRT) use in New Zealand women aged 45-64 years from 1991-1997.
Methods: For each of two population-based surveys, 2,000 women aged 45-64 years were randomly selected from the electoral roll and sent questionnaires. The response rates were 78% in 1991 and 73% in 1997.
Results: Current use of HRT increased from 12% in 1991 to 20% in 1997 (OR=2.0, 95% CI (1.6, 2.4)). In both surveys, professional women or those with husbands in professional occupations were more likely to use HRT. Women in all socio-economic and educational groups experienced a two fold increase in the use of HRT from 1991 to 1997. The majority started HRT primarily or partly for relief of symptoms (85% in 1991, 83% in 1997). While almost half had started it to prevent osteoporosis in both surveys, there was a marked increase between 1991 and 1997 in the proportion of women who had started it to prevent coronary heart disease (13% in 1991, 25% in 1997, p=0.0002). In each survey, just over a quarter of women had undergone a hysterectomy and they were 2-3 times more likely to be using HRT than other women.
Conclusions: In New Zealand the prevalence of HRT use has doubled in the 1990s, despite uncertainties about the magnitude of benefits and risks of its long-term use.