School of Public Health, Sun Yat-sen University, Guangzhou, China.
Shanghai Typhoon Institute, China Meteorological Administration, Shanghai, China.
Environ Health Perspect. 2020 Jan;128(1):17006. doi: 10.1289/EHP5117. Epub 2020 Jan 7.
Both extreme heat and air pollution exposure during pregnancy have been associated with preterm birth; however, their combined effects are unclear.
Our goal was to estimate the independent and joint effects of heatwaves and fine particulate matter [PM in aerodynamic diameter ()], exposure during the final gestational week on preterm birth.
Using birth registry data from Guangzhou, China, we included 215,059 singleton live births in the warm season (1 May-31 October) between January 2015 and July 2017. Daily meteorological variables from 5 monitoring stations and concentrations from 11 sites were used to estimate district-specific exposures. A series of cut off temperature thresholds and durations (2, 3, and 4 consecutive d) were used to define 15 different heatwaves. Cox proportional hazard models were used to estimate the effects of heatwaves and exposures during the final week on preterm birth, and departures from additive joint effects were assessed using the relative excess risk due to interaction (RERI).
Numbers of preterm births increased in association with heatwave exposures during the final gestational week. Depending on the heatwave definition used, hazard ratios (HRs) ranged from 1.10 (95% CI: 1.01, 1.20) to 1.92 (1.39, 2.64). Associations were stronger for more intense heatwaves. Combined effects of exposures and heatwaves appeared to be synergistic () for less extreme heatwaves (i.e., shorter or with relatively low temperature thresholds) but were less than additive () for more intense heatwaves.
Our research strengthens the evidence that exposure to heatwaves during the final gestational week can independently trigger preterm birth. Moderate heatwaves may also act synergistically with exposure to increase risk of preterm birth, which adds new evidence to the current understanding of combined effects of air pollution and meteorological variables on adverse birth outcomes. https://doi.org/10.1289/EHP5117.
孕期极端高温和空气污染暴露均与早产相关，但两者的联合效应尚不清楚。
本研究旨在评估孕晚期热浪和细颗粒物（空气动力学直径小于等于 2.5 微米的颗粒物）暴露对早产的独立和联合影响。
利用中国广州的出生登记数据，纳入 2015 年 1 月至 2017 年 7 月暖季（5 月 1 日至 10 月 31 日）的 215059 例单胎活产儿。采用来自 5 个监测站的逐日气象变量和 11 个站点的浓度数据，估计各地区的暴露情况。采用 2、3 和 4 连续天的不同温度阈值和持续时间定义了 15 种不同的热浪。采用 Cox 比例风险模型估计孕晚期最后 1 周的热浪和 暴露对早产的影响，并通过交互作用的超额相对风险（RERI）评估非相加性联合效应的偏离情况。
随着孕晚期热浪暴露的增加，早产人数也随之增加。根据使用的热浪定义，危险比（HR）范围为 1.10（95%置信区间：1.01，1.20）至 1.92（1.39，2.64）。热浪强度越高，相关性越强。对于较弱的热浪，暴露与热浪的联合效应似乎呈协同作用（），但对于强度较高的热浪，联合效应则小于相加作用（）。
本研究结果进一步证实了孕晚期暴露于热浪会独立引发早产。中度热浪与 暴露联合可能会协同增加早产的风险，这为空气污染和气象变量对不良出生结局的联合效应的现有认识提供了新的证据。
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