title: Risk factors for bronchiolitis hospitalization during the first year of life in a multicenter Italian birth cohort.
abstract: BACKGROUND
  Respiratory Syncytial Virus (RSV) is one of the main causes of respiratory infections during the first year of life. Very premature infants may contract more severe diseases and 'late preterm infants' may also be more susceptible to the infection. The aim of this study is to evaluate the risk factors for hospitalization during the first year of life in children born at different gestational ages in Italy.
  
  
  METHODS
  A cohort of 33-34 weeks gestational age (wGA) newborns matched by sex and age with two cohort of newborns born at 35-37 wGA and > 37 wGA were enrolled in this study for a three-year period (2009-2012). Hospitalization for bronchiolitis (ICD-9 code 466.1) during the first year of life was assessed through phone interview at the end of the RSV season (November-March) and at the completion of the first year of life.
  
  
  RESULTS
  The study enrolled 2314 newborns, of which 2210 (95.5 %) had a one year follow-up and were included in the analysis; 120 (5.4 %) were hospitalized during the first year of life for bronchiolitis. Children born at 33-34 wGA had a higher hospitalization rate compared to the two other groups. The multivariate analysis carried out on the entire population associated the following factors with higher rates for bronchiolitis hospitalization: male gender; prenatal treatment with corticosteroids; prenatal exposure to maternal smoking; singleton delivery; respiratory diseases in neonatal period; surfactant therapy; lack of breastfeeding; siblings <10 years old; living in crowded conditions and/or in unhealthy households and early exposure to the epidemic RSV season. When analysis was restricted to preterms born at 33-34 wGA the following variables were associated to higher rates of bronchiolitis hospitalization: male gender, prenatal exposure to maternal smoking, neonatal surfactant therapy, having siblings <10 years old, living in crowded conditions and being exposed to epidemic season during the first three months of life.
  
  
  CONCLUSIONS
  Our study identified some prenatal, perinatal and postnatal conditions proving to be relevant and independent risk factors for hospitalization for bronchiolitis during the first year of life. The combination of these factors may lead to consider palivizumab prophylaxis in Italy.
authors.affiliation: Pediatrics and Neonatology Unit, Imola Hospital, Imola, Italy. m.lanari@ausl.imola.bo.it.
authors.forename: Marcello
authors.initials: M
authors.lastname: Lanari
authors.affiliation: Institute of Biomedical Technologies, National Research Council, Milan, Italy. federica.prinelli@itb.cnr.it.|Department of Food, Environmental and Nutritional Sciences, University of Milan, Milan, Italy. federica.prinelli@itb.cnr.it.
authors.forename: Federica
authors.initials: F
authors.lastname: Prinelli
authors.affiliation: Institute of Biomedical Technologies, National Research Council, Milan, Italy. fulvio.adorni@itb.cnr.it.
authors.forename: Fulvio
authors.initials: F
authors.lastname: Adorni
authors.affiliation: Foundation IRCCS Santa Lucia, Rome, Italy. s.disanto@hsantalucia.it.
authors.forename: Simona
authors.initials: S
authors.lastname: Di Santo
authors.affiliation: Neonatology Unit S.Orsola-Malpighi Hospital, Via Massarenti 11, Bologna, Italy. silviavandini@gmail.com.
authors.forename: Silvia
authors.initials: S
authors.lastname: Vandini
authors.affiliation: Pediatric Pulmonology and Allergy Unit, Istituto Giannina Gaslini, Genoa, Italy. michelasilvestri@ospedale-gaslini.ge.it.
authors.forename: Michela
authors.initials: M
authors.lastname: Silvestri
authors.affiliation: Institute of Biomedical Technologies, National Research Council, Milan, Italy. massimo.musicco@itb.cnr.it.|Foundation IRCCS Santa Lucia, Rome, Italy. massimo.musicco@itb.cnr.it.
authors.forename: Massimo
authors.initials: M
authors.lastname: Musicco
mesh_terms: D001942:Breast Feeding; D001990:Bronchiolitis, Viral / Q000453:epidemiology* / Q000821:virology; D015331:Cohort Studies; D003441:Crowding; D005260:Female; D005865:Gestational Age; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007558:Italy / Q000453:epidemiology; D008297:Male; D015999:Multivariate Analysis; D018357:Respiratory Syncytial Virus Infections / Q000150:complications / Q000453:epidemiology; D012307:Risk Factors; D012737:Sex Factors