Cardiac Autonomic Changes in Shift Workers as Assessed by Time-Domain Measures of Short-Term Heart Rate Variability

Document Type : Original Article

Authors

1 Department of Physiology, PSG Institute of Medical Sciences and Research, Coimbatore, Tamil Nadu, India – 641004

2 Institute of Community Medicine, Madras Medical College, Chennai, Tamil Nadu, India – 600003.

Abstract

Background: The global prevalence of shift work is estimated to be around 20%.  Due to its untimely work schedule shift work affects the sleep-wake cycle and increases cardiovascular risk. Autonomic dysfunction is one of the explanatory links that has been proposed. Here, we strived to gather evidence regarding this association by assessing the cardiac autonomic activity of shift workers using Heart Rate Variability (HRV). Materials and methods:30 shift workers and 30-day workers were enrolled for the study as per the set criteria and subjected to Time-domain analysis of short-term HRV. By appropriate statistical methods, Time-domain indices between shift workers and day workers were compared based on their gender and Body Mass Index (BMI) and individual HRV measures were correlated with BMI. Results: Shift workers had a significantly lower RMSSD [Square Root of the Mean of the Sum of the Squares of the Differences between adjacent NN (normal-to-normal) intervals] (p- .004) and pNN50 (number of pairs of adjacent NN intervals differing more than 50 milliseconds divided by the total number of NN intervals) (p- .015) when compared to the day workers. Shift working males had a reduced RMSSD (p- .012) and pNN50 (p- .03). Shift workers showed a negative correlation between their BMI and time-domain measures SDNN (Standard Deviation of all NN intervals) (r-0.020) and RMSSD (r-0.005). Conclusion: Our study shows that shift work exposure is detrimental to cardiac autonomic activity and especially males are at a higher risk. Obesity in shift workers increases the risk.

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