Postmenopausal hormone therapy initiation before and after the Women's Health Initiative in two French cohorts.

Objectives: The aim of this study was to describe the evolution of hormone therapy (HT) initiation among newly postmenopausal women after the release of the first results from the Women's Health Initiative trial (July 2002).

Methods: We used data from two French prospective cohorts, E3N and GAZEL. We identified 3,364 women with natural menopause onset occurring before 2002 and 1,880 women with menopause onset occurring after 2002.

Results: After 2002, the age-standardized rate of HT initiation (no later than 1 y after menopause onset) in newly postmenopausal women fell by 69.9% (67.9% and 74.8% in the E3N and GAZEL cohorts, respectively). There were also changes in the distribution of both the route of administration of estrogen and the type of associated progestogen, which made transdermal estrogen plus progesterone the predominant HT type initiated after 2002 (43.6% of the initiated HT, 44.0% and 42.2% in the Étude Épidémiologique auprès de femmes de l'Éducation Nationale and GAZEL cohorts, respectively).

Conclusions: The evolution of HT initiation was similar in these two French cohorts, with a substantial drop in HT initiation rate accompanied by changes in the types of HT used.