title: The association between ambient temperature and preterm birth in Shenzhen, China: a distributed lag non-linear time series analysis.
abstract: A few studies have examined the association between ambient temperature and preterm birth (PTB), and the results have been inconsistent. This study explored the association between ambient temperature and PTB in Shenzhen, China.
  
  
  
  Data of daily singleton PTB, air pollution and meteorological variables from 2005 to 2011 were collected in Shenzhen. A distributed lag non-linear model (DLNM) was used to investigate the association of the low and high temperatures (1st, 5th, 95th, and 99th percentiles) with PTB.
  
  
  
  The median temperature was 24.5 °C and the 1st, 5th, 95th, and 99th percentiles of daily mean temperatures were 9, 12.5, 29.9 and 30.7 °C, respectively. The prevalence of singleton PTB was 5.61 % in Shenzhen. The association between temperature and PTB was not linear. There was an immediate positive association of low temperature (1st and 5th percentiles) and a negative association of high temperature (95th and 99th percentiles) with PTB. The effect of low temperature 9 °C (1st) on PTB on the current day was stronger than that of 12.5 °C (5th), with a relative risk (RR) of 1.54 (95 % CI: 1.36-1.75) and 1.49 (95 % CI: 1.35-1.63), respectively. The cumulative RR (up to 30 days) of 9 and 12.5 °C was 1.72 (95 % CI: 1.28-2.33) and 1.96 (95 % CI: 1.60-2.39), respectively. The cumulative effects (up to 30 days) of high temperature (95th and 99th percentiles) on PTB were 0.69 (95 % CI: 0.60-0.80) and 0.62 (95 % CI: 0.52-0.74), respectively. The cumulative effect (up to 30 days) of low temperatures on vaginal delivery PTB was lower than that of the cesarean section PTB with an RR of 1.58 (95 % CI: 1.12-2.22) and 1.93 (95 % CI: 1.21-3.08), respectively.
  
  
  
  This study suggests that low temperature might be a risk factor, while high temperature might be a protective factor of PTB in Shenzhen.
authors: Department of Public Health, Guangdong Women And Children Hospital, 521, 523 Xing Nan Street, Panyu District, 511442, Guangzhou, Guangdong, China.
authors: Zhijiang
authors: Z
authors: Liang
authors: Department of Children Health Care, Shenzhen Women and Children Hospital, Shenzhen, Guangdong, China.
authors: Yan
authors: Y
authors: Lin
authors: Department of Public Health, Guangdong Women And Children Hospital, 521, 523 Xing Nan Street, Panyu District, 511442, Guangzhou, Guangdong, China.
authors: Yuanzhu
authors: Y
authors: Ma
authors: Department of Information Network, Meteorological Bureau of Shenzhen Municipality, Shenzhen, Guangdong, China.
authors: Lei
authors: L
authors: Zhang
authors: Department of Public Health, Fu Tian Maternal and Children Health Hospital, Shenzhen, Guangdong, China.
authors: Xue
authors: X
authors: Zhang
authors: Department of Public Health, Luo Hu Maternal and Children Health Hospital, Shenzhen, Guangdong, China.
authors: Li
authors: L
authors: Li
authors: Department of Public Health, Long Gang Maternal and Children Health Hospital, Shenzhen, Guangdong, China.
authors: Shaoqiang
authors: S
authors: Zhang
authors: Department of Public Health, Bao An Maternal and Children Health Hospital, Shenzhen, Guangdong, China.
authors: Yuli
authors: Y
authors: Cheng
authors: Fu Tian Hospital of TCM, Shenzhen, Guangdong, China.
authors: Xiaomei
authors: X
authors: Zhou
authors: Guangdong Provincial Institute of Public Health, Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, Guangdong, China.
authors: Hualiang
authors: H
authors: Lin
authors: Department of Public Health, Guangdong Women And Children Hospital, 521, 523 Xing Nan Street, Panyu District, 511442, Guangzhou, Guangdong, China.
authors: Huazhang
authors: H
authors: Miao
authors: Department of Public Health, Guangdong Women And Children Hospital, 521, 523 Xing Nan Street, Panyu District, 511442, Guangzhou, Guangdong, China. zqgfrost@126.com.
authors: Qingguo
authors: Q
authors: Zhao
mesh_terms: D000293:Adolescent; D000328:Adult; D000397:Air Pollution / Q000032:analysis; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D008875:Middle Aged; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology*; D012306:Risk; D012307:Risk Factors; D013696:Temperature; D055815:Young Adult
keywords: Ambient temperature; Distributed lag non-linear model; Preterm birth; Time-series study