The long-term effects of tibolone on aortic stiffness and endothelial function

OBJECTIVE: To investigate the effect of 10 years of treatment with tibolone on aortic stiffness and endothelial function. DESIGN: Cross-sectional study of women currently participating in an open-label, non-randomized study of the long-term efficacy of tibolone. A total of 113 recently postmenopausal women were recruited in 1988. Fifty-eight agreed to take tibolone 2.5 mg daily and 55 were followed during the study as matched controls (who chose not to take any form of hormone replacement therapy (HRT) for the duration of the study). The groups were matched for age, weight and time since last menstrual period. SETTING: A Central London Teaching Hospital. SUBJECTS: After 10 years, 60 women remained in the study, 32 in the tibolone group and 28 in the control group. All of these women were invited to participate in this pilot study and attend the Menopause Research Unit. Fourteen women from each group agreed to attend. The main outcome measures were aortic stiffness, measured by pulse wave velocity, and endothelial function, as assessed by flow-mediated dilatation of the brachial artery. RESULTS: Pulse wave velocity was significantly lower in the tibolone group (10.4 +/- 1.2) than in the control group (11.6 +/- 1.2), p = 0.042. The flow-mediated dilatations were similar in both groups. CONCLUSION: In this study, long-term use of tibolone over 10 years has a beneficial effect on aortic stiffness. The differences seen in brachial artery vasoreactivity failed to reach statistical significance. Whether this is a true indication of the effects of long-term tibolone on brachial artery vasoreactivity will only be determined by performing a larger, placebo-controlled, randomized study.