Association Between Maternal Exposure to Magnetic Field Nonionizing Radiation During Pregnancy and Risk of Attention-Deficit/Hyperactivity Disorder in Offspring in a Longitudinal Birth Cohort
Authors: De-Kun Li, Hong Chen, Jeannette R. Ferber, Andrew K. Hirst, Roxana Odouli
Journal: JAMA Network Open (2020)

<h3>Importance</h3> An association between maternal exposure to magnetic field (MF) nonionizing radiation during pregnancy and the risk of attention-deficit/hyperactivity disorder (ADHD) has been reported in both animal and human studies. <h3>Objectives</h3> To determine whether maternal exposure to high levels of MF nonionizing radiation is associated with an increased risk of ADHD in offspring by using more accurate measurements of MF nonionizing radiation levels and physician-diagnosed ADHD, rather than self-reports, and to determine whether the association differs for the subtypes of ADHD with or without immune-related comorbidities. <h3>Design, Setting, and Participants</h3> A longitudinal birth cohort study was conducted at Kaiser Permanente Northern California among 1482 mother-child pairs whose mothers were participants of an existing birth cohort and whose level of exposure to MF nonionizing radiation was captured during pregnancy in 2 studies conducted from October 1, 1996, to October 31, 1998, and from May 1, 2006, to February 29, 2012. The offspring were followed up from May 1, 1997, to December 31, 2017. <h3>Exposure</h3> All participating women wore a monitoring meter for 24 hours during pregnancy to capture the level of exposure to MF nonionizing radiation from any sources. <h3>Main Outcomes and Measures</h3> Physician-diagnosed ADHD and immune-related comorbidities of asthma or atopic dermatitis up to 20 years of age in offspring captured in the Kaiser Permanente Northern California electronic medical record from May 1, 1997, to December 31, 2017. Confounders were ascertained during in-person interviews during pregnancy. Cox proportional hazards regression was used to account for follow-up time and confounders, and analyses were conducted on continuous scales and with categorial exposure levels. No corrections were made for multiple comparisons. <h3>Results</h3> Among the 1454 mother-child pairs (548 white [37.7%], 110 African American [7.6%], 325 Hispanic [22.4%], 376 Asian or Pacific Islander [25.9%], and 95 other or unknown [6.5%]; mean [SD] maternal age, 31.4 [5.4] years]), 61 children (4.2%) had physician-diagnosed ADHD. For adjusted continuous scale analyses, children whose mothers were exposed to high levels of MF nonionizing radiation were not associated with higher risk of ADHD (HR, 1.1; 95% CI, 0.8-1.5). Similar results were observed for children with ADHD that persisted into adolescence (HR, 1.3; 95% CI, 0.9-1.9). In categorical analyses of the children with ADHD, among 8 levels of exposures, 2 levels of exposure were associated with risk for ADHD, but 6 levels were not. In categorical analyses of children with persistent ADHD, associations were observed for 4 of 8 levels of exposure. For children with ADHD and immune-related comorbidities (asthma or atopic dermatitis), there were no associations with maternal exposure to MF nonionizing radiation in continuous scale analyses (HR, 1.2; 95% CI, 0.8-1.7), but there were associations in categorical analyses at all levels of exposure. However, the associations observed were not linear and CIs around the effect sizes were wide. <h3>Conclusions and Relevance</h3> In this study, in utero exposure to some, but not all, high levels of MF nonionizing radiation was associated with a higher risk of ADHD. However, the associations observed were inconsistent and nonlinear. The findings may spur more research to examine the biological association of in utero MF exposure with potential risk of ADHD in at-risk offspring.