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Updated: Jun 9, 2026
Calculating Heart Rate Variability from ECG Data from Youth with Cerebral Palsy During Active Video Game Sessions
Published on: June 5, 2019
Circadian variation of heart rate variability among welders
Jennifer M Cavallari1, Shona C Fang, Murray A Mittleman
1Harvard School of Public Health, Department of Environmental Health, Environmental and Occupational Medicine and Epidemiology Program, 665 Huntington Ave, FXB-103, Boston, MA 02115, USA. jcavalla@hsph.harvard.edu
Objective:
To compare the circadian variation of hourly heart rate variability (HRV) on work and non-workdays among boilermaker construction workers.
Method:
A panel study of 18 males monitored by 24-h ambulatory ECG over 44 observation-days on paired work and non-workdays was conducted. ECGs were analysed and the SD of normal-to-normal beats index (SDNN(i)) was calculated from 5-min data and summarised hourly. SDNN(i)s over work and non-workdays were compared using linear mixed-effects models to account for repeated measures and harmonic regression to account for circadian variation.
Results:
Both work and non-work hourly HRV exhibited circadian variation with an increase in the evening and a decrease in the afternoon. SDNN(i) was lower on workdays as compared with non-workdays with the largest, statistically significant differences observed between 10:00 and 16:00, during active working. Lower SDNN(i), albeit smaller yet statistically significant differences, was also observed in the evening hours following work (17:00-21:00) and early morning (4:00). In regression models using all time periods, an average workday SDNN(i) was 8.1 ms (95% CI -9.8 to -6.3) lower than non-workday SDNN(i). The circadian pattern of HRV exhibited two peaks which differed on work and non-workdays.
Conclusion:
While workday and non-workday HRV followed a circadian pattern, decreased HRV and variation of the circadian pattern were observed on workdays. Declines and changes in the circadian pattern of HRV is a concern among this exposed population.
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