Impacts of High Temperature on Adverse Birth Outcomes in Seoul, Korea: Disparities by Individual- and Community-Level Characteristics

摘要

Introduction: Relatively few studies examined the effect of temperature on adverse birth outcomes and effect modifiers of these associations. We investigated associations between heat exposure and adverse birth outcomes and evaluated how individual and community characteristics affect these associations using birth data in Seoul, Korea, 2004-2012. Methods: Logistic regression was applied to estimate the association between heat index during pregnancy, 4 weeks before delivery, and 1 week before delivery and adverse birth outcomes (preterm birth and term low birth weight). Models were adjusted for infant's sex, mother's age, mother's educational level, birth year, birth month, and air pollution level. We investigated effect modification by individual (infant's sex, mother's age and educational level) and community characteristics (gu-level SES and percentage of green areas of residential address). We also evaluated associations by combinations of individual-and community-level SES. Results: An interquartile range increase (5.5℃) in heat index during pregnancy, 4 weeks before delivery, and 1 week before delivery was associated with an odds ratio of 1.033 (95% CI 1.005,1.061), 1.019 (95% CI 1.010, 1.029), and 1.018 (95% CI 1.009, 1.027) for preterm birth, respectively. We did not find significant associations with term low birth weight. Higher risk of heat on preterm birth was associated with some individual characteristics such as infants with younger or older mother and lower community-level SES. For combinations of individual- and community-level SES, the highest and most significant estimated effect was for infants with low educated mothers living in lower community-level SES. Conclusions: Our findings have implications for the protection of infants from high heat and for future studies evaluating impacts of high temperatures on adverse birth outcomes. Our results help identify which subpopulations and factors are most relevant for disparities in this association.