title: Serum carotenoid and tocopherol concentrations and risk of asthma in childhood: a nested case-control study.
abstract: BACKGROUND
  The antioxidant hypothesis regarding the risk of asthma in childhood has resulted in inconsistent findings. Some data indicate that the role of antioxidants in childhood asthma risk may have a critical time window of effect, but only a well-designed longitudinal cohort study can clarify this hypothesis.
  
  
  OBJECTIVE
  To study the longitudinal associations between serum carotenoid and tocopherol concentrations during the first 4 years of life and asthma risk by the age of 5 years.
  
  
  METHODS
  Based on a case-control design nested within a Finnish birth cohort, 146 asthma cases were matched to 270 controls on birth time, sex, genetic risk, and birth place. Non-fasting blood samples were collected at the ages of 1, 1.5, 2, 3, and 4 years and serum carotenoids and tocopherols were analysed. Parents reported the presence and age at start of persistent doctor-diagnosed asthma in the child at the age of 5 years. Data analyses were conducted using generalized estimating equations.
  
  
  RESULTS
  We did not find strong associations between serum carotenoids and tocopherols and the risk of asthma based on age-specific and longitudinal analyses. Both lower and higher quarters of α-carotene and γ-tocopherol increased the risk of asthma.
  
  
  CONCLUSIONS
  The current findings do not support the suggestion that the increased prevalence of asthma may be a consequence of decreased intake of antioxidant nutrients. Moreover, we did not confirm any critical time window of impact of antioxidants on asthma risk. Replication of these findings in similar longitudinal settings will strengthen this evidence base.
authors.affiliation: School of Health Sciences, University of Tampere, Tampere, Finland.
authors.forename: N
authors.initials: N
authors.lastname: Hämäläinen
authors.affiliation: School of Health Sciences, University of Tampere, Tampere, Finland.|Asthma UK Centre for Applied Research, Centre for Medical Informatics, Usher Institute of Population Health Sciences and Informatics, The University of Edinburgh, Edinburgh, UK.
authors.forename: B I
authors.identifier: http://orcid.org/0000-0002-2876-6089
authors.initials: BI
authors.lastname: Nwaru
authors.affiliation: The Genomics and Biomarkers Unit, Department of Health, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: I
authors.initials: I
authors.lastname: Erlund
authors.affiliation: School of Health Sciences, University of Tampere, Tampere, Finland.|Nutrition Unit, Department of Health, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: H-M
authors.initials: HM
authors.lastname: Takkinen
authors.affiliation: School of Health Sciences, University of Tampere, Tampere, Finland.|Tampere Center for Child Health Research, School of Medicine, Tampere University Hospital, University of Tampere, Tampere, Finland.|The Science Centre of Pirkanmaa Hospital District, Tampere, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Ahonen
authors.affiliation: Department of Physiology, Institute of Biomedicine, University of Turku, Turku, Finland.|Department of Pediatrics, Turku University Hospital, Turku, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Toppari
authors.affiliation: Immunogenetics Laboratory, Faculty of Medicine, University of Turku and Turku University Hospital, Turku, Finland.|Department of Clinical Microbiology, University of Eastern Finland, Kuopio, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Ilonen
authors.affiliation: Department of Pediatrics, PEDEGO Research Unit, Medical Research Center, Oulu University Hospital and University of Oulu, Oulu, Finland.
authors.forename: R
authors.initials: R
authors.lastname: Veijola
authors.affiliation: Children's Hospital, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland.|Folkhälsan Research Center, Helsinki, Finland.|Research Programs Unit, Diabetes and Obesity, University of Helsinki, Helsinki, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Knip
authors.affiliation: Public Health Medicine, University of Helsinki and Helsinki University Hospital, University of Helsinki, Helsinki, Finland.|Department of Pediatrics, Tampere University Hospital, Tampere, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Kaila
authors.affiliation: School of Health Sciences, University of Tampere, Tampere, Finland.|Nutrition Unit, Department of Health, National Institute for Health and Welfare, Helsinki, Finland.|Tampere Center for Child Health Research, School of Medicine, Tampere University Hospital, University of Tampere, Tampere, Finland.|The Science Centre of Pirkanmaa Hospital District, Tampere, Finland.
authors.forename: S M
authors.initials: SM
authors.lastname: Virtanen
mesh_terms: D000975:Antioxidants; D001249:Asthma / Q000097:blood* / Q000453:epidemiology*; D002338:Carotenoids / Q000097:blood*; D016022:Case-Control Studies; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D016017:Odds Ratio; D063868:Patient Outcome Assessment; D015995:Prevalence; D012306:Risk; D024505:Tocopherols / Q000097:blood*
chemical_list: D000975:Antioxidants; D002338:Carotenoids; D024505:Tocopherols
keywords: antioxidants; asthma; carotenoids; children; longitudinal study; tocopherols; vitamin A; vitamin E