Title: Impact of Ambient Air Pollution on Infant Bronchiolitis in Puget Sound
1Impact of Ambient Air Pollution on Infant
Bronchiolitis in Puget Sound
- The Border Air Quality Study Team
- University of Washington Catherine Karr, Kristin
Miller, Jane Koenig, Tim Larson, Tim Gould - ckarr_at_u.washington.edu
2Study Questions
- Primary
- Do longer term (chronic) increases in ambient air
pollution impact risk of hospitalization or
clinic visits for bronchiolitis? - Which pollutants and sources (traffic, woodsmoke)
are most important? - Secondary
- Do shorter term (acute-subchronic) increases in
air pollution increase risk?
3Study Design Overview
- 1. Identify all births and one year health follow
up in Puget Sound region - 2. Assign PM2.5 exposures to individual subjects
-
- ambient monitor network data (version 1)
- ?
- geospatial traffic indicators
- ?
- modeling traffic exposure and woodsmoke
(versions 2,3) - 3. Explore risk of increasing exposures on
bronchiolitis - focus of presentation today
4Version I traditionalExposure Assessment
- Exposure windows constructed based on daily
averages of PM2.5 at nearest monitor (within 20
km) - Chronic exposure Lifetime average (from date
left hospital after birth to date of
hospitalization for bronchiolitis)
5Health Data Source
- WA State Dept. of Health Birth Events Registry
Database (BERD) - BERD birth certificate/vital statistics data
linked to hospitalization data for all
mother/infants - Includes geocoded residential address at birth
6Health Data Source
- Eligible subjects
- Singleton, livebirths for King, Snohomish,
Pierce, Kitsap county - Ambient PM2.5 monitor within 20 km of geocoded
birth address - Information on gestational age
7Population based Cohort
- Puget Sound
- 241,136 infant livebirths available for analysis
(1997-2002) - 3,113 hospitalization cases for bronchiolitis
- ICD 9CM 466.11, 466.19 (RSV vs. other infectious
etiology)
8Puget Sound PM2.5 and bronchiolitis
hospitalization
- Analysis nested case control, conditional
logistic regression - All cases from original birth cohort and up to 10
randomly selected controls matched on (/-7
days) - date of birth
- gestational age
- length of birth hospitalization
- Case N 2,770, Control N 24,009
9Confounders
- Infant sex
- Mothers smoking during pregnancy
- Infant race/ethnicity
- Parity
- Mothers education
- Insurance type
- Public assistance program involvement
10Exposure windows
- Exposure windows for case and their matched
controls all referenced to case admission date - Since matched on DOB, exposure windows are all
contemporaneous - Variability in exposure is spatial only
11Subject Chronic PM2.5 exposure
12Odds ratios for bronchiolitis hospitalization by
quartiles of chronic PM2.5 exposure
13Adj OR bronchiolitis hospitalization per 10
mcg/m3 ? chronic PM2.5 exposureby age at
diagnosis
14Adj OR bronchiolitis hospitalization per 10
mcg/m3 ? chronic PM2.5 exposureby age at
diagnosis
15Sensitivity analysis of subject distance to
monitor
Adjusted for sex, smoking during pregnancy, mom
education, parity, family income, infant
race/ethnicity
16Odds ratios for bronchiolitis hospitalization and
acute-subchronic PM2.5 exposures
17Summary Effects of PM2.5 on infant bronchiolitis
in the Puget Sound
- Suggests increased risk in bronchiolitis
hospitalization with higher PM2.5 exposure but
not statistically significant - Effect estimates highest for long term exposure
window (chronic) vs acute-subacute exposure
windows
18Summary Effects of PM2.5 on infant bronchiolitis
in the Puget Sound
- Sensitivity analyses revealed effects more
prominent for - RSV Blitis compared to Blitis due to other
infectious agents - Youngest infants (diagnosed in first 3 months of
life) - Subjects with monitor within 5 km
19Next steps
- Increase sample size by adding subjects born in
2003 -
- Evaluate effects with version 2 (improved spatial
resolution) exposure assessment -
- ? non differential exposure misclassification
-
- More variability in exposure among subjects
-
-
20Next steps
- Evaluate effects of PM2.5 on infant mortality
- Evaluate effects on pre term birth and low birth
weight
21Thanks. Questions/comments?