Postmenopausal hormone therapy: less favourable risk-benefit ratios in healthy Dutch women

To estimate the health effects of postmenopausal hormone therapy used for 10 or 20 years in a population of intermediate cardiovascular risk.

Using existing estimates of the effect of hormone therapy on rates of myocardial infarction, hip fracture and breast cancer, a proportional multistage life table was generated to calculate the effects of use for 10 and 20 years in a synthetic cohort of Dutch women aged 55 with an average and a high-risk profile for cardiovascular disease.

A woman of the general population who starts hormone therapy at age 55 for 10 years can prolong her life by 1 month and may postpone the occurrence of first incidence of one of the diseases under consideration by 2.4 months. One excess breast cancer case is likely to occur per 5-6 averted cases of first myocardial infarction or hip fracture. If she prolongs her use to 20 years, the gain of life expectancy and disease-free life expectancy is doubled. The risk-benefit ratio worsens to one extra breast cancer per 3-4 averted cases of the preventable diseases. For a woman with a high-risk profile, the gains in health are about twice as high as for her counterpart in the general population, and her risk-benefit ratio is also more favourable. Yet, the risk-benefit ratio still worsens for 20 as compared with 10 years of use.

Women from the general population in the Netherlands and similar populations can achieve only a modest gain in life expectancy by using hormones during 10 or 20 years following menopause. This is a consequence of the low incidence of myocardial infarction and hip fracture and the relatively high incidence of breast cancer before the age of 75. Women at increased cardiovascular risk can benefit more from hormone therapy. But even amongst these women, the risk of breast cancer incurred with long-term use offsets much of the benefit that could accrue from changing the risk of heart disease and hip fracture.