A study published this week in the journal Obstetrics & Gynecology shows that hormone use among postmenopausal women has been declining for at least the past decade. The study, which examined data from the National Health and Nutrition Examination Survey, found that less than 5% of postmenopausal women used hormone therapy in 2009. In contrast, that number was just over 22% in 1999.

The study found that hormone therapy use among white women sharply declined starting in 2003. The same decline followed for black and Hispanic women starting in 2005. Not coincidentally, the Women’s Health Initiative announced in 2002 that combined estrogen/progestin hormone therapy can raise certain health risks for women.

Reuters quotes the lead author of the study, Brian Sprague of the University of Vermont, as stating that he is unable to say definitively why the change is occurring, though he does speculate that fears of the health risks of hormone therapy from doctors and patients is likely the cause.

The Woman’s Health Initiative is a health initiative created by the U.S. National Institutes of Health to conduct research into the health issues that concern older women. In it’s 2002 study, it found that estrogen plus progestin hormone therapy increases the risk of heart attack, stroke, blood clots, and breast cancer. The initiative did not, however, suggest that women not use hormone therapy to alleviate symptoms of menopause. Instead, it recommended that women follow the Food and Drug Administration’s advice on hormone therapy, which suggests taking the lowest dose for the least amount of time necessary.