Background: Shift working inclusive of night shift working can severely compromise the autonomic nervous system. Since there is limited literature available about cardiac autonomic activity in shift workers compared to regular (9 am- 5 pm) workers, the purpose of our study is to assess the impact of shift working on Heart Rate Variability (HRV), by comparing HRV measures of shift workers to regular workers.

Material and Methods: the study was conducted in Department of Physiology, Gajra Raja Medical College, Gwalior. The participants were security guards working in the same gated community with same working hours, but employed in day and night shifts. 30 cases comprised of 30 night shift guards and 30 controls were 30 day shift guards (total subjects being 60). 5 minute ECG samples were obtained for each respective group at shift beginning and shift end via computerized 12 lead ECG equipment and HRV analysis was done in time domain and frequency domain parameters. Comparisons were done done between cases and controls by independent T test within 95% CI.

Results: time domain parameters SDNN and RMSSD exhibited significantly diminished values in night shift workers. Frequency domain analysis showed sympathetic dominance (LF nu, LF/HF ratio) and parasympathetic suppression (HF nu) in night shift workers.

Conclusion: night shift working leads to a sympathetic dominant state in cardiac autonomic function, combined with diminished parasympathetic activity, which is detrimental to cardiovascular health.