Treatment adherence in the Estonian postmenopausal hormone therapy (EPHT) trial [ISRCTN35338757].

Objective: To investigate treatment adherence and factors related to non-adherence in the Estonian postmenopausal hormone therapy (EPHT) trial.
Methods: A total of 1823 postmenopausal women aged 50-64 years were recruited into the EPHT trial from 1999 to 2001. They were randomised into the blind group receiving continuous orally administered postmenopausal hormone therapy (PHT) or a placebo and to a non-blind group receiving open-label PHT or no drugs. A woman was classified as non-adherent, if she had stopped treatment for at least 6-month period in treatment arms or used PHT for at least 6-month period in the control group. Adherence was calculated by the Kaplan-Meier method, and factors affecting adherence were studied with Cox proportional hazard modelling.
Results: The rate of adherent women declined approximately 50% during the first year in all treatment arms. Less than 10% of the control group women started taking prescribed PHT. Older women, with lower education, with only one birth, never used oral contraceptives (OC), with lower physical activity or who were dissatisfied with the information received from the trial staff, were more likely to discontinue. In treatment arms, the two most often cited reasons for non-adherence were side-effects and woman's loss of interest in participation. Control group women started PHT due to the menopausal symptoms or on doctor's recommendation.
Conclusions: The adherence was similar to that found for PHT use in everyday life. Higher adherence was related to younger age, higher education, previous OC use, physical activity and satisfaction with received information.