title: Acute Otitis Media During Infancy: Parent-reported Incidence and Modifiable Risk Factors.
abstract: Age at exposure to acute otitis media (AOM) risk factors such as day care attendance, lack of breastfeeding and tobacco smoke is little studied but important for targeting AOM prevention strategies. Moreover, studies are typically restricted to clinically diagnosed AOM, while a significant subset can occur outside the health care system, depending on the country setting. This study aims to determine risk factor exposure and effect of its timing within the first year of life on parent-reported AOM symptom episodes.
  
  
  
  In the WHeezing and Illnesses STudy LEidsche Rijn birth-cohort study, 1056 children were prospectively followed during their first year of life. Group day care attendance, breastfeeding and tobacco smoke exposure were recorded monthly and parent-reported AOM symptoms daily. Generalized estimating equations were used to estimate the association between the time-varying risk factors and AOM symptom episodes, while correcting for confounding by indication.
  
  
  
  The first-year incidence rate of parent-reported AOM was 569/1000 child-years [95% confidence interval (CI): 523-618]. Children who attended day care had higher odds of developing AOM symptom episodes compared with those not attending (odds ratio: 5.0; 95% CI: 2.6-9.6). Tobacco smoke exposure and (a history of) breastfeeding were not associated with AOM. Test for interaction revealed that the effect of day care increased with each month younger in age.
  
  
  
  First-year day care attendance is a major risk factor for AOM symptom episodes among infants in the community. This adjusted effect estimate is higher than previously reported and is age-dependent. AOM prevention strategies in day care facilities should therefore focus in particular on the youngest age groups.
authors.affiliation: From the *Julius Center for Health Sciences and Primary Care, and †Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Annemarijn C
authors.initials: AC
authors.lastname: Prins-van Ginkel
authors.forename: Patricia C J
authors.initials: PC
authors.lastname: Bruijning-Verhagen
authors.forename: Cuno S P M
authors.initials: CS
authors.lastname: Uiterwaal
authors.forename: Cornelis K
authors.initials: CK
authors.lastname: van der Ent
authors.forename: Henriette A
authors.initials: HA
authors.lastname: Smit
authors.forename: Marieke L A
authors.initials: ML
authors.lastname: de Hoog
mesh_terms: D000208:Acute Disease / Q000453:epidemiology*; D003631:Day Care, Medical; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D010033:Otitis Media / Q000453:epidemiology*; D010290:Parents; D011446:Prospective Studies; D012307:Risk Factors