title: [Chronic lung disease in a cohort of children born before the 28th gestational week. Incidence and etiological factors].
abstract: BACKGROUND
  Advances in perinatal care have increased the survival rate of extremely preterm (ETP) infants during the last decades. A key factor has been the ability to provide respiratory support with mechanical ventilation. Mechanical ventilation, however, is associated with pulmonary disease, such as bronchopulmonary dysplasia (BPD). A national prospective study of all EPT infants born in 1994-95 in Denmark found a low incidence of chronic lung disease (CLD), defined as oxygen dependence at 36 weeks postnatal age. In the cohort of surviving infants (n = 195), the incidence of CLD was 15% (95% CI: 11-19). Only 46% of the surviving children had been mechanically ventilated during the neonatal period, and this factor was proposed as an explanation of the low percentage of infants with CLD.
  
  
  METHODS
  The present study evaluated CLD in a cohort of EPT infants born in 1998-2001 at Rigshospitalet, the university hospital in Copenhagen. The incidence of CLD was compared to that found in the cohort born in 1994-1995 and the data from the two cohorts were analysed together to investigate changes in CLD.
  
  
  RESULTS
  Although only 39% had been treated with mechanical ventilation in the neonatal period, as many as 37% (95% CI: 31-43) of the surviving children in the study (n = 220) had CLD. Analysing the data from the cohort born in 1994-95 and the cohort born in 1998-2001 together, the increase in CLD could be explained by an improved survival rate and a lower gestational age and birth weight in the 1998-2001 cohort.
  
  
  CONCLUSIONS
  Our results support the theory that CLD in EPT infants results from insults other than mechanical ventilation.
authors.affiliation: H:S Rigshospitalet, Juliane Marie Centret, Neonatalafdelingen.
authors.forename: Tina Irene
authors.initials: TI
authors.lastname: Hentze
authors.forename: Bo Mølholm
authors.initials: BM
authors.lastname: Hansen
authors.forename: Finn
authors.initials: F
authors.lastname: Jonsbo
authors.forename: Gorm
authors.initials: G
authors.lastname: Greisen
mesh_terms: D002908:Chronic Disease; D015331:Cohort Studies; D045422:Continuous Positive Airway Pressure; D003718:Denmark / Q000453:epidemiology; D005865:Gestational Age; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D007234:Infant, Premature; D007235:Infant, Premature, Diseases / Q000401:mortality / Q000628:therapy*; D008171:Lung Diseases / Q000453:epidemiology / Q000209:etiology / Q000401:mortality; D010102:Oxygen Inhalation Therapy; D011379:Prognosis; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000009:adverse effects*; D012307:Risk Factors