What happens to a woman’s health risks after she stops using hormone therapy (HT) following five to seven years of use? Until recently, there was little rigorous scientific data to address this question. Now: New findings from the Women’s Health Initiative (WHI) study provide an answer.

At the start of the WHI, in the mid-1990s, more than 16,000 women ages 50 to 79 were assigned to take either a combination of estrogen plus progestin (Prempro) or a placebo for 5.6 years. After they stopped taking the pills, the women were tracked for three more years. Good news: The risks for heart attack, stroke and blood clots, which rose while women were taking HT, quickly dropped back toward normal after HT was stopped. Bad news: Benefits of HT—relief from hot flashes, protection against bone loss and fractures—also dissipated quickly…a slightly higher risk for breast cancer persisted…and there was a suggestion of a higher risk for various cancers and for death in the post-HT years.

Significance: These findings reinforce current guidelines advising women to consider HT only for short-term relief from moderate-to-severe menopausal hot flashes or night sweats that significantly disrupt their quality of life and/or sleep. Ideally, treatment should be limited to two to three years or, at most, five years.

Although HT does help prevent fractures, it is no longer recommended as a first line of defense against osteoporosis. Reason: The average age of women who break a hip is close to 80 years, so women would need to take HT for many, many years to maintain bone protection when fracture risk is greatest.

Keys to safety: Health status and timing. HT-related heart attack, stroke and blood clot risks are low for women in good cardiovascular health whose periods ended less than 10 years ago, but higher in those who are older and/or in poorer cardiovascular health. Example: Among women who entered the WHI trial with better cholesterol levels, those assigned to HT had a 40% lower risk for coronary heart disease than those on a placebo…but among women who entered with worse cholesterol levels, HT users had a 73% higher risk.

The balance of benefits and risks of HT appears quite favorable for younger women. Among WHI participants in their 50s, HT use was linked to a 30% reduction in mortality. This does not mean that healthy, recently menopausal women should take HT specifically to prevent health problems—rather, when taking HT for short-term symptom management, such women need not be overly concerned about risks.

What’s next: More research is needed to determine if lower doses of oral HT or transdermal patches or gels can further minimize risk.