Acupoint Sensitivity in Patients with Primary Insomnia and Its Correlation with Polysomnography and Heart Rate Variability: A Cross-Sectional Study

Background: Primary insomnia (PI) is the most common clinical sleep disorder that can be effectively treated with acupuncture. However, the selection of optimal acupoints remain contentious. Objective: To investigate the pain sensitization phenomenon of specific acupoints commonly used in treating PI, we evaluated the threshold and sensitization rate of acupoint sensitization and their correlations with sleep questionnaire scores, polysomnography (PSG) and heart rate variability (HRV) to identify the optimal sensitized points. Methods: This study recruited 73 PI patients and 73 age- and sex-matched healthy controls in the outpatient acupuncture clinic of the Third Affiliated Hospital of Zhejiang University of Traditional Chinese Medicine from January 31, 2024 to March 31, 2025. Pressure pain thresholds (PPT) were tested at 10 specific points commonly used in PI. The primary outcome measure was calculated as the acupoint hyperalgesia rate using the receiver operating characteristic (ROC) curve. Secondary outcome measures included PSG and HRV indices of some subjects. Results: Compared with the control group, PI patients showed significantly lower PPTs at specific acupoints such as RN14 and BL15, along with increased pain sensitivity rates. The pain sensitization rate in the T5-T8 nerve segments of PI patients was markedly elevated. Additionally, the degree of acupoint pain sensitization was negatively correlated with age and positively correlated with disease duration. Higher PSQI scores were associated with a greater likelihood of pain sensitization at EX-HN3, EX-HN0, and HT7. The probability of GV20 pain sensitization increased with higher SDS scores but decreased with increased high-frequency components in HRV. Conclusion: Pain sensitization was observed at specific points commonly used in PI patients. BL15 and RN14 may be the best acupoints for clinical diagnosis and treatment. Furthermore, acupoint pain sensitization was correlated with age, high-frequency, disease duration, PSQI, and SDS. Acupoint pain sensitization can be used as a screening and assessment index for acupuncture treatment in insomnia patients, providing an objective basis for individualized treatment. Keywords: primary insomnia, acupoint sensitization, polysomnography, heart rate variability, case-control study