title: Young maternal age at delivery is associated with asthma in adult offspring.
abstract: OBJECTIVE
  Some studies have shown an association between lower maternal age at delivery and increased asthma in children and young adults. It is unclear whether this represents an effect of maternal ageing or a protective effect of siblings. In a North-European population based study, we investigated whether mother's age at delivery was associated with risk for asthma and hay fever in adult offspring, taking into account relevant confounders.
  
  
  METHODS
  A total of 16,190 subjects (74%) aged 23-54 yr answered a postal questionnaire in a follow-up of the European Community Respiratory Health Survey (ECRHS I).
  
  
  RESULTS
  The associations of maternal age at delivery with hay fever, respiratory symptoms and diagnosed asthma were analysed using logistic regression, adjusting for household size, dwelling, parental education, centre, gender, adult hay fever, smoking, age and body mass index (BMI). The adjusted odds ratios (95% CI) for wheeze with breathlessness, wheeze without a cold and asthma in the offspring were 0.94 (0.90-0.99), 0.89 (0.86-0.94) and 0.92 (0.88-0.97), respectively, per 5 yr increase in maternal age. No heterogeneity between centres was found (p=0.84). The estimates remained similar in sub-sample analyses when adjusting for siblings, maternal smoking (n=3109) and for birth weight (n=1686). Hay fever was more common among those with the youngest and oldest mothers.
  
  
  CONCLUSIONS
  In this large North-European multi-centre study, asthma was less common with increasing maternal age. This effect was consistent between centres and persisted with adjustment for several potential confounders, suggesting that the association may possibly be explained by biological changes related to maternal ageing.
authors.affiliation: Department of Thoracic Medicine, Haukeland University Hospital, N-5021 Bergen, Norway. birger.lerum@helse-bergen.no
authors.forename: Birger N
authors.initials: BN
authors.lastname: Laerum
authors.forename: Cecilie
authors.initials: C
authors.lastname: Svanes
authors.forename: Tore
authors.initials: T
authors.lastname: Wentzel-Larsen
authors.forename: Amund
authors.initials: A
authors.lastname: Gulsvik
authors.forename: Kjell
authors.initials: K
authors.lastname: Torén
authors.forename: Eva
authors.initials: E
authors.lastname: Norrman
authors.forename: Thorarinn
authors.initials: T
authors.lastname: Gíslason
authors.forename: Christer
authors.initials: C
authors.lastname: Janson
authors.forename: Ernst
authors.initials: E
authors.lastname: Omenaas
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001249:Asthma / Q000196:embryology / Q000453:epidemiology / Q000209:etiology*; D004812:Epidemiologic Methods; D005060:Europe / Q000453:epidemiology; D005191:Family Characteristics; D005260:Female; D006801:Humans; D008297:Male; D008423:Maternal Age; D008875:Middle Aged; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D006255:Rhinitis, Allergic, Seasonal / Q000196:embryology / Q000453:epidemiology / Q000209:etiology