A cross-sectional study was conducted in China to investigate the relationship between self-assessed sleep status and electromagnetic field exposures, especially power frequency magnetic fields, in workers of a power plant.
Sleep quality was assessed by asking the participants to evaluate the sleep quality and the sleep duration during the past month. Sleep duration was categorized in short (< 7 h), medium (7-8 h), and long (≥ 8 h).
|Reference group 1||daily occupational exposure time: ≤ 1.5 hours/day|
|Group 2||daily occupational exposure time: < 1.5 - ≤ 4 hours/day|
|Group 3||daily occupational exposure time: > 4 hours/day|
|Reference group 4||occupational exposure duration: < 23 years|
|Group 5||occupational exposure duration: ≥ 23 years|
|Reference group 6||electric fee: < 150 yuan/month|
|Group 7||electric fee: ≥ 150 yuan/month|
|Reference group 8||mobile phone use: < 12 years|
|Group 9||mobile phone use: ≥ 12 years|
The measured electric field strength was 316.3 ± 1212.3 V/m and magnetic field strength was 6.17 ± 14.71 µT in the exposure group, which far outstripped the values in the non-exposure group (3.9 ± 0.3 V/m and 0.061 ± 0.017 µT, respectively).
Subjects with long daily exposure time had a significantly higher risk of poor sleep quality (group 2: OR 1.68, CI 1.18-2.39; group 3: OR 1.57, CI 1.10-2.24) in comparison to those with short daily exposure time (group 1). Additionally, among the subjects with long-term occupational exposure, the longer daily occupational exposure time apparently increased the risk of poor sleep quality (> 1.5 - ≤4 hours/day: OR 2.12 CI 1.23-3.66; > 4 hours/day: OR 1.83, CI 1.07-3.15). There was no significant association of long-term occupational exposure duration, monthly electric fee or years of mobile-phone use with sleep quality or sleep duration.
The authors conclude that the results showed an association between daily occupational power frequency magnetic field exposure and poor sleep quality. It implies that power frequency magnetic field exposure may damage human sleep quality rather than sleep duration.