Exposure to Acute Air Pollution and Risk of Otitis Media

Abstract

Background/Aim: Infants may be more susceptible to illness as a result of altered immune function due to exposure to particulate matter less than 2.5µm in diameter (PM2.5). Our aim is to estimate associations between acute increases in PM2.5 exposure and risk of otitis media among births born 2001 through 2008 in Massachusetts, United States. Methods: We analyzed 42,336 first time otitis media clinical encounter visits (hospitalizations, emergency department visits, and observational stays) using a case-crossover study design. PM2.5 was estimated using satellite, remote sensing, meteorological and land use data based on geocoded birth address. We used conditional logistic regression models adjusted for temperature, humidity, atmospheric pressure, and holiday using a semi-symmetric bidirectional referent design per 10-µg/m3 increase in PM2.5. We examined the influence of PM2.5 on (1) symptom exacerbation using very short exposure lags of 0 and 1 day and (2) susceptibility to infection using longer exposure lags of 4 and 7 days. To determine susceptible subgroups, effect modification was assessed by gestational age, birth weight, season of diagnosis, subsequent clinical encounter, insurance payer codes, median income by census block group, infant sex, breastfeeding initiation in hospital at birth, age of infant at time of clinical encounter and maternal race. Results: Preterm infants were at substantially increased risk of otitis media 4 days (Odds Ratio (OR) = 1.09, 95% Confidence Interval (CI) = 1.02-1.16) and 7 days (OR = 1.08, 95% CI = 1.02-1.15) prior to clinical encounter. The association betweenPM2.5 exposureand otitis media clinical encounters was significantly different by gestational age (lag4 p=0.03; lag 7 p=0.02). There was no further evidence of effect modification. Overall, we found non-significant positive associations with otitis media across all lags. Conclusions: Preterm infants are more susceptible to otitis media associated with acute PM2.5 exposures compared to full term infants.