Emma Hitt, PhD
ugust 1, 2011 — Exposure to high levels of magnetic fields during pregnancy may increase the risk for asthma in offspring, according to new epidemiologic findings, published online August 1 in the Archives of Pediatrics & Adolescent Medicine.
According to the researchers, led by De-Kun Li, MD, PhD, from the Division of Research at the Kaiser Foundation Research Institute, Kaiser Permanente, Oakland, California, recent studies suggest that electromagnetic fields could adversely affect reproductive outcomes and the immune system, and may have a direct effect on brain cell activities. "Therefore, it is conceivable that exposure to high [electromagnetic frequencies], especially during pregnancy (the period of fetal development), may have an impact on the risk of asthma in offspring," they write.
To investigate this association further, the researchers conducted a prospective cohort study of pregnant women whose daily exposure to magnetic fields was captured objectively by a meter during pregnancy. Their 626 children were followed for asthma diagnosis for up to 13 years after they were born.
Overall, 130 children (20.8%) of the study participants developed asthma during 13 years of follow-up, with more than 80% of children diagnosed by 5 years of age.
A linear relationship was observed between increasing maternal median daily level of magnetic field exposure in pregnancy and an increased risk for asthma in offspring; every 1-mG increase of maternal magnetic field level during pregnancy was associated with a 15% increased rate of asthma in their children (adjusted hazard ratio, 1.15; 95% confidence interval [CI], 1.04 - 1.27).
In addition, compared with the children whose mothers had a low magnetic field level (median 24- hour magnetic field level, ≤ 0.3 mG) during pregnancy, those whose mothers had a high magnetic field level (> 2.0 mG) had more than a 3.5-fold increased rate of asthma (adjusted hazard ratio, 3.52; 95% CI, 1.68 - 7.35). By comparison, children whose mothers had a medium magnetic field level (> 0.3 - 2.0 mG) had a 74% increased rate of asthma (adjusted hazard ratio, 1.74; 95% CI, 0.93 - 3.25).
They also found a synergistic interaction between the magnetic field effect and 2 well-established asthma risk factors: a maternal history of asthma and birth order — namely, being first-born.
"The underlying pathogenesis of asthma is likely structural and due to functional defects in epithelium and an impaired innate immune system," Dr. Li and colleagues note. "Prenatal exposure to high magnetic field levels could interfere with the development of both epithelial cells and normal immune systems," they add.
"[T]he findings of the present study open up a new area in understanding the risk factors for asthma and the health effects of ubiquitous [magnetic field] exposure, especially during pregnancy," they conclude. "As with any epidemiological study, these findings need to be replicated. If confirmed, they have the potential to inform new intervention strategies to reduce asthma, the most prevalent chronic disease among children."
The study was supported in part by a grant from the California Public Health Foundation. The authors have disclosed no relevant financial relationships.
Arch Pediatr Adolesc Med. Published online August 1, 2011.
اللَّهُمَّ نَجِّ الْمُسْتَضْعَفِينَ مِنَ الْمُؤْمِنِينَ اللَّهُمَّ اشْدُدْ وَطْأَتَكَ عَلَى مُضَرَ اللَّهُمَّ اجْعَلْهَا عَلَيْهِمْ سِنِينَ كَسِنِي يُوسُفَ