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- Title
Effects of shift work on QTc interval and blood pressure in relation to heart rate variability.
- Authors
Murata, Katsuyuki; Eiji Yano; Hashimoto, Hideki; Karita, Kanae; Dakeishi, Miwako
- Abstract
Objectives:There is evidence that shift work contributes to excess cardiovascular mortality. The purpose of this study was to determine the effects of shift work on heart rate-corrected QT (QTc) and blood pressure in relation to heart rate variability (CVRR).Methods:The study population consisted of 153 male shiftworkers and 87 male day workers who were employed at a copper-smelting plant. The QTc interval, total power spectral density (t-PSD) of 100 RR intervals, PSDs with frequencies of 0.01 Hz-0.15 Hz and 0.15 Hz-0.40 Hz (PSDLF and PSDHF), CVRR, low frequency (LF) component variability and high frequency (HF) component variability (CCVLF and CCVHF) and %LF (PSDLF/(PSDLF+PSDHF) ·100) were measured (LF and HF components are thought to reflect the sympathetic and parasympathetic activities, respectively).Results:The QTc interval was significantly longer in the shiftworkers than in the day workers, although there was no significant difference in systolic or diastolic blood pressure between the two groups. Also, the CCVLF and log(PSDLF) were significantly depressed in the shiftworkers. In the day workers, the QTc interval was significantly related to the CVRR, log(t-PSD), CCVHF, log(PSDHF),%LF, and log(LF/HF ratio) (partial correlation coefficientr=-0.305, -0.377, -0.312, -0.355, 0.297, and 0.277, respectively). In the shiftworkers only two relations of the QTc interval to non-specific CVRR and log(t-PSD) were significant.Conclusion:The clear association between long QTc interval and reduced parasympathetic activity observed in the day workers did not exist in the shiftworkers. Rather, the shiftworkers had a selective reduction in sympathetic drive, which may have compensated for prolonged QTc interval due to shift work. On the other hand, the impact of shift work on hypertension remains unclear, although reduced sympathetic drive in the shiftworkers may explain the absence of differences in blood pressure between shiftworkers and day workers to some extent.
- Subjects
SHIFT systems; WORKING hours; HEART beat; CARDIOVASCULAR diseases; BLOOD pressure; MORTALITY
- Publication
International Archives of Occupational & Environmental Health, 2005, Vol 78, Issue 4, p287
- ISSN
0340-0131
- Publication type
Article
- DOI
10.1007/s00420-004-0592-4