Eun Mi Jung1, Kyoung-Nam Kim2, Hyesook Park3, Hwashin H Shin4, Hae Soon Kim5, Su Jin Cho5, Soon Tae Kim6, Eun Hee Ha7. 1. Department of Occupational and Environmental Medicine, Ewha Womans University, Seoul, Republic of Korea; Ewha Global Health Institute for Girls, Ewha Womans University, Seoul, Republic of Korea. 2. Division of Public Health and Preventive Medicine, Seoul National University Hospital, Seoul, Republic of Korea. 3. Department of Preventive Medicine, Ewha Womans University, Seoul, Republic of Korea. 4. Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada; Department of Mathematics and Statistics, Queen's University, Kingston, ON, Canada. 5. Department of Pediatrics, Ewha Womans University, Seoul, Republic of Korea. 6. Department of Environmental and Safety Engineering, Ajou University, Suwon, Republic of Korea. 7. Department of Occupational and Environmental Medicine, Ewha Womans University, Seoul, Republic of Korea; Ewha Global Health Institute for Girls, Ewha Womans University, Seoul, Republic of Korea. Electronic address: eunheeha@ewha.ac.kr.
Abstract
BACKGROUND: Findings from previous studies on the association between exposure to fine particulate matter (PM2.5) and the risk of infant mortality were inconsistent. Thus, two main objectives of our study were to examine the association between exposure to PM2.5 and specified infant mortality and to identify critical trimesters. METHODS: We retrospectively created a birth cohort of singleton full-term infants born in South Korea between 2010 and 2015 using national birth and infant mortality data. The specified causes of infant mortality were circulatory and respiratory diseases, perinatal conditions, congenital anomalies, and sudden infant death syndrome. We performed 1:10 propensity score matching for various exposure windows: each trimester, prenatal, and postnatal (up to age 1). Conditional logistic regression was applied to estimate odds ratios (ORs) and 95% confidence intervals (CIs), while accounting for gestational age, birth weight, maternal education level, season of birth, and regions (metropolitan areas/provinces). We also conducted sex-stratified analyses and used different matching ratios for sensitivity analyses. RESULTS: A total of 2,501,836 births and 761 deaths (0.03%) were identified in the birth cohort. We found an increased risk of infant mortality per 10 µg/m3 increase in PM2.5 exposure during the prenatal period (OR: 1.29, 95% CI: 1.07-1.55). Exposure in the 1st and 2nd trimesters was linked to an elevated risk (OR: 1.19, 95% CI: 1.02-1.37; OR: 1.21, 95% CI: 1.04-1.40). However, no association was shown in the third trimester. PM2.5 exposure in the 1st and 2nd trimesters was associated with elevated male infant mortality, but did not reach statistical significance in female infants. The use of different matching ratios did not significantly affect the results. CONCLUSION: The study findings suggest that exposure to PM2.5 could affect infant mortality differently by the timing of exposure and sex, which suggests a relation to fetal development. However, further investigations are warranted.
BACKGROUND: Findings from previous studies on the association between exposure to fine particulate matter (PM2.5) and the risk of infant mortality were inconsistent. Thus, two main objectives of our study were to examine the association between exposure to PM2.5 and specified infant mortality and to identify critical trimesters. METHODS: We retrospectively created a birth cohort of singleton full-term infants born in South Korea between 2010 and 2015 using national birth and infant mortality data. The specified causes of infant mortality were circulatory and respiratory diseases, perinatal conditions, congenital anomalies, and sudden infant death syndrome. We performed 1:10 propensity score matching for various exposure windows: each trimester, prenatal, and postnatal (up to age 1). Conditional logistic regression was applied to estimate odds ratios (ORs) and 95% confidence intervals (CIs), while accounting for gestational age, birth weight, maternal education level, season of birth, and regions (metropolitan areas/provinces). We also conducted sex-stratified analyses and used different matching ratios for sensitivity analyses. RESULTS: A total of 2,501,836 births and 761 deaths (0.03%) were identified in the birth cohort. We found an increased risk of infant mortality per 10 µg/m3 increase in PM2.5 exposure during the prenatal period (OR: 1.29, 95% CI: 1.07-1.55). Exposure in the 1st and 2nd trimesters was linked to an elevated risk (OR: 1.19, 95% CI: 1.02-1.37; OR: 1.21, 95% CI: 1.04-1.40). However, no association was shown in the third trimester. PM2.5 exposure in the 1st and 2nd trimesters was associated with elevated male infant mortality, but did not reach statistical significance in female infants. The use of different matching ratios did not significantly affect the results. CONCLUSION: The study findings suggest that exposure to PM2.5 could affect infant mortality differently by the timing of exposure and sex, which suggests a relation to fetal development. However, further investigations are warranted.