Air pollution in the week prior to delivery and preterm birth in 24 Canadian cities: a time to event analysis.
Air pollution
Preterm birth
Time-to-event
Journal
Environmental health : a global access science source
ISSN: 1476-069X
Titre abrégé: Environ Health
Pays: England
ID NLM: 101147645
Informations de publication
Date de publication:
03 01 2019
03 01 2019
Historique:
received:
13
07
2018
accepted:
07
12
2018
entrez:
5
1
2019
pubmed:
5
1
2019
medline:
14
2
2019
Statut:
epublish
Résumé
Numerous studies have examined the association between air pollution and preterm birth (< 37 weeks gestation) but findings have been inconsistent. These associations may be more difficult to detect than associations with other adverse birth outcomes because of the different duration of exposure in preterm vs. term births, and the existence of seasonal cycles in incidence of preterm birth. We analyzed data pertaining to 1,001,700 singleton births occurring between 1999 and 2008 in 24 Canadian cities where daily air pollution data were available from government monitoring sites. In the first stage, data were analyzed in each city employing Cox proportional hazards models using gestational age in days as the time scale, obtaining city-specific hazard ratios (HRs) with their 95% confidence intervals (CIs) expressed per interquartile range (IQR) of each air pollutant. Effects were examined using distributed lag functions for lags of 0-6 days prior to delivery, as well as cumulative lags from two to six days. We accounted for the potential nonlinear effect of daily mean ambient temperature using a cubic B-spline with three internal knots. In the second stage, we pooled the estimated city-specific hazard ratios using a random effects model. Pooled estimates across 24 cities indicated that an IQR increase in ozone (O We observed associations between daily O
Sections du résumé
BACKGROUND
Numerous studies have examined the association between air pollution and preterm birth (< 37 weeks gestation) but findings have been inconsistent. These associations may be more difficult to detect than associations with other adverse birth outcomes because of the different duration of exposure in preterm vs. term births, and the existence of seasonal cycles in incidence of preterm birth.
METHODS
We analyzed data pertaining to 1,001,700 singleton births occurring between 1999 and 2008 in 24 Canadian cities where daily air pollution data were available from government monitoring sites. In the first stage, data were analyzed in each city employing Cox proportional hazards models using gestational age in days as the time scale, obtaining city-specific hazard ratios (HRs) with their 95% confidence intervals (CIs) expressed per interquartile range (IQR) of each air pollutant. Effects were examined using distributed lag functions for lags of 0-6 days prior to delivery, as well as cumulative lags from two to six days. We accounted for the potential nonlinear effect of daily mean ambient temperature using a cubic B-spline with three internal knots. In the second stage, we pooled the estimated city-specific hazard ratios using a random effects model.
RESULTS
Pooled estimates across 24 cities indicated that an IQR increase in ozone (O
CONCLUSIONS
We observed associations between daily O
Identifiants
pubmed: 30606207
doi: 10.1186/s12940-018-0440-8
pii: 10.1186/s12940-018-0440-8
pmc: PMC6318965
doi:
Substances chimiques
Air Pollutants
0
Ozone
66H7ZZK23N
Types de publication
Journal Article
Research Support, Non-U.S. Gov't
Langues
eng
Sous-ensembles de citation
IM
Pagination
1Subventions
Organisme : Medical Research Council
ID : MR/R013349/1
Pays : United Kingdom
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