Survival Analysis of Long-Term Exposure to Different Sizes of Airborne Particulate Matter and Risk of Infant Mortality Using a Birth Cohort in Seoul, Korea

Abstract

BackgroundSeveral studies suggest that airborne particulate matter (PM) is associated with infant mortality; however, most focused on short-term exposure to larger particles.ObjectivesWe evaluated associations between long-term exposure to different sizes of particles [total suspended particles (TSP), PM ≤ 10 μm in aerodynamic diameter (PM10), ≤ 10–2.5 μm (PM10–2.5), and ≤ 2.5 μm (PM2.5)] and infant mortality in a cohort in Seoul, Korea, 2004–2007.MethodsThe study includes 359,459 births with 225 deaths. We applied extended Cox proportional hazards modeling with time-dependent covariates to three mortality categories: all causes, respiratory, and sudden infant death syndrome (SIDS). We calculated exposures from birth to death (or end of eligibility for outcome at 1 year of age) and pregnancy (gestation and each trimester) and treated exposures as time-dependent variables for subjects’ exposure for each pollutant. We adjusted by sex, gestational length, season of birth, maternal age and educational level, and heat index. Each cause of death and exposure time frame was analyzed separately.ResultsWe found a relationship between gestational exposures to PM and infant mortality from all causes or respiratory causes for normal-birth-weight infants. For total mortality (all causes), risks were 1.44 (95% confidence interval, 1.06–1.97), 1.65 (1.18–2.31), 1.53 (1.22–1.90), and 1.19 (0.83–1.70) per interquartile range increase in TSP, PM10, PM2.5, and PM10–2.5, respectively; for respiratory mortality, risks were 3.78 (1.18–12.13), 6.20 (1.50–25.66), 3.15 (1.26–7.85), and 2.86 (0.76–10.85). For SIDS, risks were 0.92 (0.33–2.58), 1.15 (0.38–3.48), 1.42 (0.71–2.87), and 0.57 (0.16–1.96), respectively.ConclusionsOur findings provide supportive evidence of an association of long-term exposure to PM air pollution with infant mortality.

Maternal exposure to heatwave and preterm birth inBrisbane,Australia

“…Furthermore, the power of the survival analysis is increased compared with a case-crossover approach because all the subjects are examined. 24,25,27 Preterm birth was defined as a live birth occurring at <37 completed weeks of gestation, according to the definition of the World Health Organization. 1 We used the Cox PHs regression model (Cox regression), which is widely used in survival analysis, with time-dependent covariates to estimate the acute effects of heatwave.…”

“…[24][25][26] The air pollution data were provided by the Queensland Department of Environment and Resource Management. Weekly average levels of meteorological factors and ambient air pollution exposures were calculated by using the original daily data.…”

The Impact of the Clean Air Act

“…Air pollution is associated with increased post-neonatal infant mortality, including sudden infant death syndrome (SIDS) [38–41]. Using time-series analyses, the relationship between daily air pollution levels and daily SIDS rates was studied in twelve Canadian cities over a sixteen year time period [40].…”

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“…Fine PM (Particulate Matter) and ozone are associated with increasing risk of mortality and respiratory morbidity, while exposure to nitrogen oxides, ozone and PM is linked with allergic responses [1].…”