Factors influencing heart rate variability in nurses following night shifts: a prospective observational clinical study

Heart rate variability (HRV) has been established as a key indicator of autonomic nervous system activity, reflecting both sympathetic and parasympathetic modulation. This study was aimed at investigating the factors that influence HRV in nurses following night shifts. A prospective, observational, single-center study was conducted in the office corridor of a tertiary hospital in southern China. Thirty-five female nurses (median age: 27.0 years) working ward shifts were enrolled; all the participants were free of severe cardiopulmonary diseases and mobility limitations. Nurses completed their routine night shifts, and electrocardiograms (ECGs) were recorded for six minutes during a standing break on the mornings of the first and second days after their shifts. The study sought to identify the factors that influenced the primary outcome, i.e., the HRV after night shifts. The study also assessed the factors that affected a secondary outcome, i.e., the HRV after a one-day recovery period. Age and the frequency of awakenings in the 24 h preceding a night shift were inversely associated with low-frequency (LF) power after the night shift. Additionally, age was an independent predictor of LF power on the first morning after the night shift. On the other hand, the total catch-up sleep duration within 24 h after a night shift was negatively correlated with the HRV the second morning following the night shift. Older nurses and those experiencing more frequent awakenings before their night shifts exhibited lower LF power on the first morning after night duty, indicating reduced autonomic activity under the measured conditions. A longer duration of catch-up sleep within 24 h after a night shift was associated with lower HRV values on the second morning, reflecting decreased autonomic activity. These findings highlight potential relationships between pre- and post-shift sleep adjustments and post-shift HRV. This study was retrospectively registered with Clinicaltrials.gov. Registration Date: August 1, 2024. Clinicaltrials.gov ID: NCT06542510.