title: Meta-analysis of prevalence of wheezing and recurrent wheezing in infants.
abstract: BACKGROUND
  Wheezing affects children's quality of life, and is related with asthma in childhood. Although prevalence of wheezing has been previously studied in several countries, there is no reference of worldwide prevalence in infants. The aim of this meta-analysis is to estimate the prevalence of wheezing and recurrent wheezing in infants aged up to two years, and compare the prevalence across world regions.
  
  
  METHODS
  Literature search was conducted in MEDLINE and SCOPUS databases, looking for observational studies published up to June 2016, including as keywords "prevalence" or "epidemiology" combined with "wheeze", "wheezing" or "asthma symptoms" and "infant" or "preschool". Fast*Pro software and random effects Bayesian model were used. Heterogeneity was estimated using I2statistic, and sensitivity analyses were performed.
  
  
  RESULTS
  We identified 109 studies after duplicates were removed. After exclusions, 14 studies were included in the meta-analysis. Prevalence of wheezing and recurrent wheezing were 36.06% (95% CI 35.17-36.96), and 17.41% (95% CI 16.74-18.09), respectively. In European countries, prevalence of wheezing was 30.68% (95% CI 28.97-32.45), and 12.35% (95% CI 11.27-13.47) for recurrent wheezing. Prevalence of wheezing and recurrent wheezing in Latin America were higher, 40.55% (95% CI 39.40-41.71), and 19.27% (95% CI 18.44-20.11), respectively. In Africa, prevalence of wheezing was 15.97% (95% CI 14.05-18.00). Low or no heterogeneity was found in all cases.
  
  
  CONCLUSIONS
  More than one third of infants suffer from wheezing and almost one fifth from recurrent wheezing, being these illnesses especially prevalent in Latin American countries, pointing out an important public health problem.
authors.affiliation: Department of Health Sciences, Public University of Navarre, Pamplona, Spain. Electronic address: alvarez.80114@e.unavarra.es.
authors.forename: I
authors.initials: I
authors.lastname: Alvarez-Alvarez
authors.affiliation: Department of Health Sciences, Public University of Navarre, Pamplona, Spain.
authors.forename: H
authors.initials: H
authors.lastname: Niu
authors.affiliation: Department of Health Sciences, Public University of Navarre, Pamplona, Spain; IDISNA, Navarre's Institute for Health Research, Pamplona, Spain; Preventive medicine, University of Navarre Clinic, Pamplona, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Guillen-Grima
authors.affiliation: Department of Health Sciences, Public University of Navarre, Pamplona, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Aguinaga-Ontoso
mesh_terms: D001249:Asthma / Q000453:epidemiology*; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015995:Prevalence; D012135:Respiratory Sounds
keywords: Epidemiology; Infants; Meta-analysis; Prevalence; Recurrent wheezing; Wheezing