Effect of extremely low frequency electromagnetic field exposure on sleep quality in high voltage substations

This study aims to investigate the effect of extremely low frequency electromagnetic fields exposure on sleep quality in high voltage substations (132, 230 and 400 KV) in Kerman city and the suburbs. For this purpose, the electric field intensity and magnetic flux density were measured in different parts of substations, and then the occupational exposure was estimated by averaging electric field intensity and magnetic flux density in a shift work. The cases comprised 67 workers who had been exposed to electromagnetic fields in age range of 24-57 and the controls were 110 persons the age ranged 24-50 years. Sleep quality of both groups was evaluated by the Pittsburgh Sleep Quality Index questionnaire (PSQI). Finally, these data were subjected to statistical analysis. The results indicated that 90.5% of cases and 85.3% of controls had the poor quality sleep according to PSQI (P-value=0.615). Total sleep quality score mean for the case and control groups were 10.22 +/- 3.4 and 9.74 +/- 3.62 (P-value=0.415), respectively. Meantime to fall asleep for cases(35.68 +/- 26.25 min) was significantly higher than for controls (28.89 +/- 20.18 min) (P-value=0.002). Cases had average sleep duration of 5.49 +/- 1.31 hours, which was lower ascompared with control subjects (5.90 +/- 1.67hours). Although there was a higher percentage for the case group with poor sleep quality than the control group, but no statistically significant difference was observed.