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Objective: To investigate the association between short-term exposure to indoor total volatile organic compounds (TVOC) and nocturnal heart rate variability (HRV) among young female adults., Methods: This panel study recruited 50 young females from one university in Beijing, China from December 2021 to April 2022. All the participants underwent two sequential visits. During each visit, real time indoor TVOC concentration was monitored using an indoor air quality detector. The real time levels of indoor temperature, relative humidity, noise, carbon dioxide and fine particulate matter were monitored using a temperature and humidity meter, a noise meter, a carbon dioxide meter and a particulate counter, respectively. HRV parameters were measured using a 12-lead Holter. Mixed-effects models were used to evaluate the association between the TVOC and HRV parameters and establish the exposure-response relationships, and two-pollutant models were applied to examine the robustness of the results., Results: The mean age of the 50 female subjects was (22.5±2.3) years, and the mean body mass index was (20.4±1.9) kg/m 2 . During this study, the median (interquartile range) of indoor TVOC concentrations was 0.069 (0.046) mg/m 3 , the median (interquartile range) of indoor temperature, relative humidity, carbon dioxide concentration, noise level and fine particulate matter concentration were 24.3 (2.7) ℃, 38.5% (15.0%), 0.1% (0.1%), 52.7 (5.8) dB(A) and 10.3 (21.5) μg/m 3 , respectively. Short-term exposure to indoor TVOC was associated with significant changes in time-domain and frequency-domain HRV parameters, and the exposure metric for most HRV parameters with the most significant changes was 1 h-moving average. Along with a 0.01 mg/m 3 increment in 1 h-moving average concentration of indoor TVOC, this study observed decreases of 1.89% (95% CI: -2.28%, -1.50%) in standard deviation of all normal to normal intervals (SDNN), 1.92% (95% CI : -2.32%, -1.51%) in standard deviation of average normal to normal intervals (SDANN), 0.64% (95% CI : -1.13%, -0.14%) in percentage of adjacent NN intervals differing by more than 50 ms (pNN50), 3.52% (95% CI : -4.30%, -2.74%) in total power (TP), 5.01% (95% CI : -6.21%, -3.79%) in very low frequency (VLF) power, and 4.36% (95% CI : -5.16%, -3.55%) in low frequency (LF) power. The exposure-response curves showed that indoor TVOC was negatively correlated with SDNN, SDANN, TP, and VLF when the concentration exceeded 0.1 mg/m 3 . The two-pollutant models indicated that the results were generally robust after controlling indoor noise and fine particulate matter., Conclusion: Short-term exposure to indoor TVOC was associated with significant negative changes in nocturnal HRV of young women. This study provides an important scientific basis for relevant prevention and control measures.