Effect of Extremely Low-frequency Magnetic Field Exposure on the Sleepiness of Night-shift Nurses: A Randomized Clinical Trial

Nurses are at higher risk of insomnia due to changes in their work shifts. This study aims to investigate the effect of extremely low-frequency magnetic field (ELF-MF) exposure on the sleepiness of night-shift nurses during rest time.

This is a randomized crossover clinical trial that was conducted on 28 night-shift nurses, randomly divided into two groups of exposure (n=14) and sham (n=14). The central areas of the brain of nurses in the exposure group was exposed to a magnetic field with 200-μT intensity at a frequency of 10Hz for 10 minutes after each night shift for eight night shifts and four weeks. The executive protocol for the sham group was the same, except that the nurses were not exposed to a magnetic field. After exposure, there was no intervention for two weeks to wash out the effects. Then, the groups exchanged their roles and the protocol was repeated. Stanford sleepiness scale (SSS) was used to measure the sleepiness of nurses. Findings were analyzed in SPSS software.

No significant difference was observed in the mean SSS score in the first and second periods between the two groups (P=0.30). No significant difference was observed in the mean SSS score between the periods and the order of placement in each period, either (carryover effect=0.97, period effect=0.96).

The local ELF-MF exposure has no significant effect on the sleepiness of night-shift nurses during rest time. It may be due to their disturbed circadian rhythm or the disturbance by the noise and light (not by work-related anxiety). Further investigation is needed.