title: Urbanization factors associated with childhood asthma and prematurity: a population-based analysis aged from 0 to 5 years in Taiwan by using Cox regression within a hospital cluster model.
abstract: OBJECTIVE
  Childhood asthma and premature birth are both common; however, no studies have reported urbanization association between asthma and prematurity and the duration of prematurity affect asthma development. We use Taiwan Longitudinal Health Insurance Database (LHID) to explore association between asthma and prematurity among children by using a population-based analysis.
  
  
  METHODS
  This is a retrospective cohort study with registration data derived from Taiwan LHID. We evaluated prematurely born infants and children aged <5 years (n = 532) and age-matched control patients (n = 60505) using Cox proportional hazard regression analysis within a hospital cluster model. Of the 61 037 examinees, 14 012 experienced asthma during the 5-year follow-up, including 161 (72.26 per 1000 person-years) infants and children born prematurely and 13 851 (40.27 per 1000 person-years) controls.
  
  
  RESULTS
  The hazard ratio for asthma during 5-year follow-up period was 1.95 (95% confidence interval = 1.67-2.28) among children born prematurely. Boys born prematurely aged 0-2 years were associated with higher asthma rates compared with girls in non-premature and premature groups. Living in urban areas, those born prematurely were associated with higher rates of asthma compared with non-prematurity. Those born prematurely lived in northern region had higher asthma hazard ratio than other regions.
  
  
  CONCLUSIONS
  Our analyses indicated that sex, age, urbanization level, and geographic region are significantly associated with prematurity and asthma. Based on cumulative asthma-free survival curve generated using the Kaplan-Meier method, infants born prematurely should be closely monitored to see if they would develop asthma until the age of 6 years.
authors.affiliation: Department of Pediatrics, Shuang Ho Hospital, Taipei Medical University , Taipei , Taiwan .
authors.forename: Sheng-Chieh
authors.initials: SC
authors.lastname: Lin
authors.forename: Hui-Wen
authors.initials: HW
authors.lastname: Lin
mesh_terms: D000367:Age Factors; D001249:Asthma / Q000453:epidemiology*; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D047928:Premature Birth / Q000453:epidemiology*; D016016:Proportional Hazards Models; D012111:Residence Characteristics; D012189:Retrospective Studies; D012307:Risk Factors; D012737:Sex Factors; D013624:Taiwan / Q000453:epidemiology; D014507:Urbanization
keywords: Asthma; epidemiology; pediatrics; prematurity; prevention; risk factors; robust sandwich variance