Objective: To evaluate the effects of tibolone on heart rate variability and plasma free fatty acid levels in postmenopausal women.
Design: Randomized, placebo-controlled trial.
Setting: University hospital.
Patient(s): Thirty postmenopausal women.
Intervention(s): Tibolone, 2.5 mg/d, or placebo for 4 months.
Main outcome measures: Variability in heart rate and changes in the lipid profile.
Result(s): Anthropometric data were unchanged throughout the study. Compared with placebo, long-term tibolone administration was associated with a decrease in plasma levels of low-density lipoprotein cholesterol, triglyceride, and free fatty acid and homeostasis model assessment index. Furthermore, tibolone administration was associated with an increase in RR interval, total power, and high frequency and decrease in low frequency and the low frequency/high frequency ratio. Finally, the delta decrease in plasma free fatty acid levels correlated with delta low frequency/high frequency ratio independently of age, delta body mass index, delta homeostasis model assessment index, and low-density lipoprotein cholesterol levels.
Conclusion(s): Long-term tibolone administration improves the ratio of cardiac sympathetic tone to parasympathetic tone in postmenopausal women.