The acute effects of temperature variability on heart rate variability: A repeated-measure study

Background: The impacts of temperature variability on cardiac autonomic function remain unclear. Objective: To explore the short-term associations between daily temperature variability and parameters of heart rate variability (HRV). Methods: This is a repeated-measure study among 78 eligible participants in Shanghai, China. We defined temperature variability as diurnal temperature range (DTR), the standard-deviation of temperature (SDT) and temperature variability (TV). We evaluated 3 frequency-domain HRV parameters (VLF, LF and HF) and 4 time domain parameters (SDNN, SDANN, rMSSD and pNN50). We used linear mixed-effect models to analyze the data after controlling for environmental and individual confounders. Results: Temperature variability was significantly associated with decreased HRV, especially on the concurrent day. The exposure-response relationships were almost inversely linear for most parameters. Every one inter quartile range (IQR) increase of DTR was associated with a decrease of 3.92% for VLF, 6.99% for LF, 5.88% for HF, 3.94% for rMSSD and 1.30% for pNN50. Each IQR increase of SDT was associated with a decline of 6.48% for LF, 5.91% for HF, 4.26% for rMSSD and 1.87% for pNN50. Every IQR increase of SDT was associated with a decrease of 4.39% for VLF, 7.67% for LF, 6.52% for HF, 3.22% for SDNN, 2.98% for SDANN, 4.05% for rMSSD, and 1.41% for pNN50. The decrements in HRV associated with temperature variability were more prominent in females. Conclusion: Temperature variability on the concurrent day could significantly decrease cardiac autonomic function, especially in females.

Automated summary

The study found that temperature variability is negatively associated with heart rate variability, especially on the same day. The exposure-response relationships were almost linear for most parameters. The increase in temperature variability is significantly associated with the decrease in heart rate variability, with females being more affected.