title: Birth order, atopy, and symptoms of allergy and asthma among inner-city children attending Head Start in New York City.
abstract: BACKGROUND
  In past research, children with older siblings were more likely than others to wheeze at age 2 years, but less likely by age 6 years. Higher infection transmission and a down-regulated allergic immune response as a result of these infections, respectively, were suggested as the causes. However, in a study of children aged 0-3 years in a low-income urban community in New York City, USA, with high asthma prevalence, we observed no birth-order effect.
  
  
  OBJECTIVE
  To evaluate the association between birth order and atopy and respiratory symptoms in 4-year-old children attending Head Start programs in NYC.
  
  
  METHODS
  Respiratory symptoms were assessed by questionnaire for 1005 children (mean age 4.0 years) living in high asthma prevalence neighbourhoods. Serum was collected from a subgroup of the children (n=494) and specific IgE responses to dust mite, cockroach, mouse, and cat allergens were measured.
  
  
  RESULTS
  Prevalence of specific IgE (> or =0.35 IU/mL) did not differ significantly among first (35%), second (35%), and later-born children (28%) (P=0.23). Increasing birth order was associated with increasing prevalence of respiratory symptoms in the prior year, including wheeze (first 20%, second 27%, third or later 35%; P<0.001), being awakened at night by cough (28%, 33%, 38%; P=0.005), emergency department visits (14%, 17%, 21%; P=0.02) and hospitalizations for difficulty breathing (6.1%, 6.6%, 10%; P=0.04). The associations of birth order with respiratory symptoms were statistically significant only for the non-seroatopic children and those without an asthmatic parent.
  
  
  CONCLUSIONS
  Non-seroatopic children with older siblings were more likely than those without older siblings to have respiratory symptoms at age 4 years. Although the stability of these associations over time remains to be determined, the differences in findings between this study and our previous NYC birth cohort study suggest that patterns of asthma development may vary even among low-income populations within the same city.
authors: Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, NY 10032, USA. mp2217@columbia.edu
authors: M S
authors: MS
authors: Perzanowski
authors: S M
authors: SM
authors: Canfield
authors: G L
authors: GL
authors: Chew
authors: R B
authors: RB
authors: Mellins
authors: L A
authors: LA
authors: Hoepner
authors: J S
authors: JS
authors: Jacobson
authors: I F
authors: IF
authors: Goldstein
mesh_terms: D000485:Allergens / Q000276:immunology; D000818:Animals; D001249:Asthma / Q000097:blood / Q000453:epidemiology* / Q000473:pathology; D001722:Birth Order; D002415:Cats; D002675:Child, Preschool; D015331:Cohort Studies; D005191:Family Characteristics; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood; D016015:Logistic Models; D008297:Male; D051379:Mice; D015999:Multivariate Analysis; D009519:New York City / Q000453:epidemiology; D010033:Otitis Media / Q000453:epidemiology; D011203:Poverty; D015995:Prevalence; D006255:Rhinitis, Allergic, Seasonal / Q000097:blood / Q000453:epidemiology* / Q000473:pathology; D012307:Risk Factors; D012737:Sex Factors; D035781:Siblings; D011795:Surveys and Questionnaires; D014505:Urban Population
chemical_list: D000485:Allergens; D007073:Immunoglobulin E