PM10 Exposure and Bronchiolitis from Respiratory Syncytial Virus among Infants

Abstract

Background: Respiratory syncytial virus (RSV) ranks first among the causes of acute lower respiratory infections in children. The most common clinical syndrome associated with RSV infection is bronchiolitis (RSV-B). Air pollution might influence the inflammatory cascade that brings to RSV-B.Aims: To investigate the association between PM10 exposure and the risk of hospitalization for RSV-B.Methods: We selected hospital discharge records (HRD) with ICD-9-CM code 466.11, referring to infants <1 year of age, and occurring in the epidemic seasons of 2012-2013 in Lombardy, Italy. Each case was assigned daily PM10 and apparent temperature (AT) levels of the provincial capital city of residence. Different time windows were considered: single days preceding hospitalization (lag 0 to 30), their average estimates (lag 0-1 to 0-30), the weeks preceding hospitalization (week 1 to 4). We applied negative binomial regression models adjusted for AT and season to the daily counts of hospital admissions in each province. Random effects meta-analyses of province-specific estimates were performed to obtain regional values. Results were expressed as incidence rate ratios (IRR) and 95% confidence intervals (95%CI) per 10µg/m3 increase in PM10 concentration.Results: 2,814 HRD were included (males = 55%). We observed an increased hospitalization risk of 6% at lag 0 and of 7% at lag 1 (95%CI: 1.03-1.10 for both). IRR ranged from 1.03 to 1.05 between lags 2 and 11, and no risk increase was observed from lag 12. Analyses on averaged daily lags showed increased risks in the two weeks preceding hospitalization, with IRR from 1.08 (1.04-1.12) at lag 0-1 to 1.15 (1.08-1.23) at lag 0-13. When considering weekly lags, a 6% (1.01-1.12) and a 7% (1.02-1.13) increased risks were observed during weeks 1 and 2, respectively.Conclusions: Our study improved the body of evidence on the association between short- and medium-term PM10 exposures and the risk of hospitalization for RSV-B among infants.