Residential exposure to power frequency magnetic field and sleep disorders among women in an urban community of northern Taiwan

STUDY OBJECTIVES: To investigate relationships between residential exposure to power frequency magnetic field and sleep initiation and maintenance disorders (SIAMD). DESIGN: A cross-sectional design conducted in an urban town of northern Taiwan in 1995-1996. SETTING/PATIENTS: A total of 5,078 married women aged 20-59. INTERVENTIONS: N/A. MEASUREMENTS: The residential magnetic field intensity was assessed using EMDEX II dosimeters. Trained interviewees collected self-reported information on SIAMD and other covariates. Three type-specific SIAMD were analyzed for associations with background, bedroom, and overall residential exposures. RESULTS: The prevalence rates of difficulty initiating sleep (DIS), difficulty maintaining sleep (DMS), and early morning awakening (EMA) were 29.5%, 38.17%, and 26.02%, respectively. The DIS prevalence was significantly associated with bedroom magnetic field exposure of 2 miliGauss (mG) (odds ratio (OR)=1.20, 95% confidence interval (CI)=1.02-1.40). The DMS prevalence was significantly higher for women with background exposure of 2 mG (OR=1.28, 95% CI=1.04-1.56). An elevated EMA prevalence was also significantly associated with all of the three exposure measures with excess risks ranging from 28% for overall exposure to 65% for background exposure. When magnetic field strength was analyzed as a continuous variable, background exposure, but not overall or bedroom exposure, showed a small but significant association with DMS and EMA (OR=1.05 per 1 mG increase, 95% CI=1.02-1.09). CONCLUSIONS: There is a modest association between residential exposures to elevated magnetic field intensity and insomnia complaints in women.