Sudan Madhuri, Arah Onyebuchi A, Becker Thomas, Levy Yael, Sigsgaard Torben, Olsen Jørn, Vergara Ximena, Kheifets Leeka
Department of Epidemiology, UCLA Fielding School of Public Health, Los Angeles, California, United States of America.
Department of Clinical Epidemiology, Aarhus University, Aarhus, Denmark.
PLoS One. 2017 May 17;12(5):e0177651. doi: 10.1371/journal.pone.0177651. eCollection 2017.
A study reported an increased risk of asthma in children whose mothers were exposed to magnetic field (MF) levels above 0.2 μT during pregnancy. We re-examined this association using data from mothers and children in the Danish National Birth Cohort (DNBC).
This study included 92,676 singleton-born children and their mothers from the DNBC. MF exposure from power lines was estimated for all residences where the mothers lived during pregnancy and for all children from birth until the end of follow up. Exposure was categorized into 0 μT, 0.1 μT, and ≥ 0.2 μT for analysis. Definitive and possible asthma cases were identified using data from three independent data sources: 1) mothers' reports, 2) a national hospitalization register, 3) a national prescription drug register. We calculated hazard ratios (HR) and 95% confidence intervals (CI) for the association between the highest level of exposure during pregnancy and asthma in children, adjusting for several potential confounding factors. We also examined the sensitivity of the risk estimates to changes in exposure and outcome definitions.
No differences or trends in the risk of asthma development were detected between children with different levels of MF exposure regardless of the asthma case definition or outcome data source. For definitive cases, the HR (95% CI) for those with any exposure was 0.72 (0.27-1.92), and it was 0.41 (0.06-2.92) for those exposed to ≥ 0.2 μT. Adjustments for confounding and variations in the exposure definition did not appreciably alter the results.
We did not find evidence that residential exposure to MF during pregnancy or early childhood increased the risk of childhood asthma. This interpretation is in line with the lack of an established biological mechanism directly linking MF exposure to asthma, but high exposure was very rare in this cohort.
一项研究报告称，母亲在孕期暴露于磁场（MF）水平高于0.2μT的环境中，其子女患哮喘的风险会增加。我们利用丹麦国家出生队列（DNBC）中母亲和儿童的数据，重新审视了这种关联。
本研究纳入了DNBC中92,676名单胎出生的儿童及其母亲。估算了母亲孕期居住的所有住所的输电线磁场暴露情况，以及所有儿童从出生到随访结束期间的磁场暴露情况。为便于分析，将暴露情况分为0μT、0.1μT和≥0.2μT。利用三个独立数据源的数据确定明确和可能的哮喘病例：1）母亲报告；2）国家住院登记册；3）国家处方药登记册。我们计算了孕期最高暴露水平与儿童哮喘之间关联的风险比（HR）和95%置信区间（CI），并对几个潜在混杂因素进行了校正。我们还研究了风险估计值对暴露和结局定义变化的敏感性。
无论哮喘病例定义或结局数据来源如何，不同磁场暴露水平的儿童在哮喘发病风险上均未发现差异或趋势。对于明确病例，任何暴露水平儿童的HR（95%CI）为0.72（0.27 - 1.92），暴露于≥0.2μT的儿童HR为0.41（0.06 - 2.92）。对混杂因素的校正和暴露定义的变化并未明显改变结果。
我们没有发现证据表明孕期或幼儿期居住环境中的磁场暴露会增加儿童患哮喘的风险。这一解释与缺乏将磁场暴露与哮喘直接联系起来的确立生物学机制相符，但在该队列中高暴露情况非常罕见。
