Effect of Sleep Quality on Heart Rate Variability in Medical Students: A Cross-sectional Study

Globally, medical students had demonstrated poor sleep quality. Poor sleep can negatively affect cardiovascular functions. The autonomic nervous system (ANS) regulates cardiovascular function during the sleep-wake cycle and can be monitored by heart rate variability (HRV). The primary objective was to determine any association between sleep quality and HRV parameters in medical students.

A cross-sectional study was conducted at a single institution in North India. The Pittsburgh Sleep Quality Index (PSQI) was used to assess sleep quality. HRV was recorded using Power Lab AD Instrument (Australia). The correlation between HRV variables and sleep parameters was estimated using Pearson's correlation coefficient and Spearman correlation based on the normality test.

A total of 84 medical students (54 males and 30 females) participated in the study. The mean total PSQI score was 6.44 (SD = 2.62). There was a statistically significant negative correlation between PSQI global score and HRV indices high frequency (HF), root mean square successive difference (RMSSD), and the proportion of differences in consecutive RR intervals that are longer than 50 ms in % (pRR50). A statistically significant positive correlation between PSQI global score and low frequency (LF), and LF/HF ratio was found.

The present study found that parasympathetic-related indices (RMSSD, pRR50, and HF) were inversely correlated to poor sleep quality and directly related to sympathetic indices (LF and LF/HF). This suggests that the poorer the sleep quality, the less is the parasympathetic activity and the more is the sympathetic activity.