Effect of ambient air pollution and temperature on the risk of stillbirth: a distributed lag nonlinear time series analy
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RESEARCH ARTICLE
Effect of ambient air pollution and temperature on the risk of stillbirth: a distributed lag nonlinear time series analysis Mehdi Ranjbaran 1,2 Kamran Yazdani 1
&
Rasool Mohammadi 3,4 & Mehdi Yaseri 1
&
Mehdi Kamari 5 & Abbas Habibelahi 6 &
Received: 29 January 2020 / Accepted: 21 September 2020 # Springer Nature Switzerland AG 2020
Abstract Objectives This study aimed to determine the effect of ambient air pollution and temperature on stillbirth in Tehran. Methods In this time-series study, the effect of O3 (ppb), CO (ppm), NO2 (ppb), SO2 (ppb), PM2.5 (μg/m3), and minimum, maximum, and mean daily temperature (°C) on stillbirth was evaluated in Tehran, Iran between March 2015 and March 2018. Using a quasi-Poisson regression model in combination with a Distributed Lag Non-linear Models (DLNM), the Relative Risk (RR) was estimated through comparing the high temperature (99th, 95th, and 75th percentiles) and low temperature (1st, 5th, and 25th percentiles) with the median. The effect of air pollution was estimated for each 1-, 5-, or 10-unit increase in the concentration during lags (days) 0–21. Results Among air pollutants, only a 5-ppm increase in the SO2 concentration in lag 0 increased the risk of stillbirth significantly (RR = 1.062; 1.002–1.125). The largest effect of heat was observed while comparing the 99th percentile of minimum daily temperature (26.9 °C) with the median temperature (13.2 °C), which was not statistically significant (RR = 1.25; 0.95–1.65). As for cold, a non-significant protective effect was observed while comparing the 1st percentile of maximum daily temperature (3.1 °C) with the median temperature (23.2 °C) (RR = 0.92; 0.72–1.19). Conclusion Each 5-ppm increase in the mean daily SO2 in lag 0 increased the risk of stillbirth by 6% while other air pollutants had no significant effects on stillbirth. In lags 0 and 1, the heat increased the risk of stillbirth while the cold had protective effects, which were not statistically significant. Keywords Stillbirth . Ambient temperature . Air pollution . Distributed lag non-linear models
Introduction * Kamran Yazdani [email protected]; [email protected] 1
Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
2
School of Public Health, Qazvin University of Medical Sciences, Qazvin, Iran
3
Department of Biostatistics and Epidemiology, School of Public Health and Nutrition, Lorestan University of Medical Sciences, Khorramabad, Iran
4
Nutritional Health Research Center, Health and Nutritional Department, Lorestan University of Medical Sciences, Khorramabad, Iran
5
Deputy of Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran
6
Neonatal Health Office, MOHME. IR IRAN, Tehran, Iran
According to the World Health Organization (WHO) estimates, 2.6 million stillbirths occur in the world annually [1] with rates ranging from 3.1 in 1000 births in high-income countries to 29 in 1000 births in Sub-Saharan Africa and 12.9 in 1000 births in
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