Heart rate variability in male shift workers in automobile manufacturing factories in South Korea
Purpose The aim of this study was to determine the effect of circadian rhythm disruption on cardiovascular autonomic regulation by examining potential differences in heart rate variability (HRV) between day- and night-shift workers.
Methods The study population consisted of 162 workers who worked both day and night shifts in two automobile manufacturing companies who underwent ambulatory 24-h electrocardiogram recording and completed questionnaires and sleep diaries. Both time and frequency domain indices of HRV were compared.
Results HRV parameters (mean RR, SDNN, RMSSD, pNN50, TP, HF, LF, LF/HF ratio) reflecting sympathetic and parasympathetic modulation varied less with activity in night-shift workers.
Conclusions Circadian rhythm-mediated changes in autonomic regulation of the cardiovascular system were blunted in night-shift workers, which could contribute to an increased risk for cardiovascular disease in overnight workers.