Combo HT linked to doubling of thrombosis risk: the risk of venous thrombosis among HT users climbs with age and increasing BMI: preliminary analysis of final WHI data.

SAN DIEGO -- Postmenopausal women who take estrogen plus progestin as hormone therapy have more than a twofold increase in risk of venous thrombosis, compared with nonusers, according to a preliminary analysis of final results from the Women's Health Initiative.

Thrombosis occurred in 167 women who received combination hormone therapy (HT), for an overall incidence of 3.5 events per 1,000 person-years. Among women who took a placebo, there were 76 events, resulting in a cumulative incidence of 1.7 events per 1,000 person-years, Dr. Mary Cushman reported at the annual meeting of the American Society of Hematology.

The analysis also found that the risk of venous thrombosis among HT users climbs with age and increasing body mass index (BMI).

"Consideration of these factors might be important in prescribing estrogen plus progestin," noted Dr. Cushman of the University of Vermont, Colchester.

In the WHI trial, 16,608 women aged 50-79 years were randomized to receive conjugated equine estrogen (0.625 mg/day) and medroxyprogesterone acetate (2.5 mg/day) or placebo. After a mean follow-up of 5.6 years, the trial was halted in July 2002 because of the overall health risks associated with the combined estrogen plus progestin therapy, including increased risks of invasive breast cancer, coronary heart disease, stroke, and pulmonary embolism.

In the first part of the analysis, Dr. Cushman and her associates used intention-to-treat principles to study the association of combination HT and baseline risk factors with the 5.6-year risk of developing venous thrombosis.

In the second part of the analysis, the researchers performed a nested case-control study, including 147 women who developed thrombosis, to examine associations of genetic variants with thrombosis risk. They selected 513 controls who were matched for age, ...