Changes in the use of hormone replacement therapy in New Zealand from 1991-1997

To describe changes in the prevalence of hormone replacement therapy (HRT) use in New Zealand women aged 45-64 years from 1991-1997.

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.

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.

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.