title: Nocturnal dry cough in the first 7 years of life is associated with asthma at school age.
abstract: BACKGROUND
  Childhood wheeze is an important, well-known risk factor for asthma, yet little is known about the contribution of nocturnal dry cough. We investigated the association of nocturnal dry cough at ages 1-7 years with doctor-diagnosed asthma at 8 years of age, both in the presence and absence of wheeze.
  
  
  METHODS
  Data of 3,252 children from the PIAMA birth cohort were studied. Parents reported the presence of nocturnal dry cough, wheeze, and doctor-diagnosed asthma in the past 12 months yearly, from birth up to the age of 8 years.
  
  
  RESULTS
  Nocturnal dry cough without wheeze was significantly associated with doctor-diagnosed asthma at age 8, except for age 1 (range of Relative Risks (RR) at ages 2-7: 1.8 (age 5) - 7.1 (age 7), all P-values <0.048). As expected, wheeze without nocturnal dry cough was strongly associated with doctor-diagnosed asthma at age 8 (range of RR: 2.0 (age 1) - 22.2 (age 7), all P-values <0.003). Of interest, nocturnal dry cough with wheeze showed the strongest association with doctor-diagnosed asthma at age 8 (range of RR: 3.7 (age 1) - 26.0 (age 7), all P-values <0.001). The relative excess risk of asthma at age 8 due to interaction of nocturnal dry cough with wheeze at age 1 year was 1.8 (0.1-3.6, P < 0.01).
  
  
  CONCLUSIONS
  Nocturnal dry cough and wheeze in early childhood are both independently associated with asthma at school age. The presence of both nocturnal dry cough and wheeze at age 1 almost doubles the risk of asthma at age 8 compared to wheeze alone.
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Epidemiology, GRIAC Research Institute, Groningen, The Netherlands.|University of Groningen, University Medical Center Groningen, Department of Pulmonary Medicine, GRIAC Research Institute, Groningen, The Netherlands.
authors.forename: Ilse M
authors.initials: IM
authors.lastname: Boudewijn
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Epidemiology, GRIAC Research Institute, Groningen, The Netherlands.
authors.forename: Olga E M
authors.initials: OE
authors.lastname: Savenije
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Pediatric Pulmonology and Pediatric Allergology, GRIAC Research Institute, Groningen, The Netherlands.
authors.forename: Gerard H
authors.initials: GH
authors.lastname: Koppelman
authors.affiliation: Centre for Prevention and Health Services Research, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Alet H
authors.initials: AH
authors.lastname: Wijga
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Henriëtte A
authors.initials: HA
authors.lastname: Smit
authors.affiliation: Department of Pediatrics, Erasmus University Medical Center, Sophia Children's Hospital, Rotterdam, The Netherlands.
authors.forename: Johan C
authors.initials: JC
authors.lastname: de Jongste
authors.affiliation: Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Gehring
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Pulmonary Medicine, GRIAC Research Institute, Groningen, The Netherlands.
authors.forename: Dirkje S
authors.initials: DS
authors.lastname: Postma
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Epidemiology, GRIAC Research Institute, Groningen, The Netherlands.
authors.forename: Marjan
authors.initials: M
authors.lastname: Kerkhof
mesh_terms: D001249:Asthma / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003371:Cough / Q000453:epidemiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D008297:Male; D009426:Netherlands / Q000453:epidemiology; D012135:Respiratory Sounds
keywords: asthma; birth cohort; children; nocturnal dry cough; wheeze