Improvement of menopausal symptoms with acupuncture not reflected in changes to heart rate variability

This pilot study investigated whether acupuncture improves menopausal symptoms and whether these improvements correlate with changes in heart rate variability (HRV), a marker of autonomic nervous system activity. The research was motivated by the need for safe alternatives to hormone therapy following the findings of the Women's Health Initiative in 2002, which linked hormone replacement to increased risks of breast cancer and thromboembolic events.

Twelve menopausal women, aged 48–62 years and with moderate to severe symptoms (minimum score of 22 on the Menopause Rating Scale), participated in the study. Participants received 10 sessions of traditional Chinese acupuncture over 4 weeks, following a standardized protocol that included body points (HT-7, PC-6, ST-36, LR-3, KI-6, SP-6, GV-20) and auricular points (Shenmen and Uterus). Sessions were held three times a week for the first two weeks, then twice a week for the next two weeks.

The methodology included continuous heart rate monitoring before, during, and after each acupuncture session, with spectral analysis of HRV to assess sympathetic and parasympathetic system activity. Menopausal symptoms were assessed daily using the Menopause Rating Scale, which measures 11 symptoms on a 0–4 point scale.

The results showed significant improvement in all 11 menopausal symptoms assessed, with reduction rates ranging from 0.17 to 0.33 points per week. The symptoms that improved most were hot flashes (-0.34 points/week), sleep disturbances (-0.31 points/week), and fatigue (-0.30 points/week). Surprisingly, vaginal dryness — a symptom rarely reported in previous acupuncture studies — also improved.

However, HRV analysis did not show a significant correlation with symptom improvement. Only one HRV measure (during acupuncture) showed a significant change, but this alteration was attributed to the discomfort of the procedure itself, not to specific therapeutic effects. Post hoc analysis of high-frequency bands also revealed no significant effects of the intervention.

An interesting finding was the high individual variability in HRV, both between participants and within the same person over time. Two participants showed distinct patterns: one with severe initial vasomotor symptoms presented rebalancing of HRV frequency bands after treatment, while another showed changes in the opposite direction.

The clinical implications suggest that, although acupuncture can provide symptomatic relief in menopause, the mechanism may not involve detectable changes in HRV. This raises questions about whether the observed benefits result from placebo effects, expectation, or nonspecific relaxation, rather than acupuncture-specific physiological mechanisms.

Limitations include the very small sample size, the absence of a control group, the possibility of type I and II errors, and the pragmatic design that did not control for variables such as concomitant medications or breathing. The study also did not use controlled breathing, which could have influenced HRV measurements, and some participants were taking medications that could affect heart rate variability.