title: The role of migration and choice of denominator on the prevalence of cerebral palsy.
abstract: OBJECTIVE
  Differential migration and choice of denominator have been hypothesized to contribute to differences between period prevalence and birth prevalence of cerebral palsy (CP). The purpose of this study was to evaluate the effects of migration and choice of denominator on the prevalence of CP.
  
  
  METHODS
  Data from the Metropolitan Atlanta Developmental Disabilities Surveillance Program and census and birth certificate files were used to calculate various CP prevalence estimates for 2000.
  
  
  RESULTS
  The overall CP period prevalence was 3.2 (95% confidence interval [CI] 2.7-3.8) per 1000 8-year-olds and was similar for those born in Atlanta who resided there at age 8 years (3.3; 95% CI 2.7-4.1) and those born outside Atlanta who moved into Atlanta by age 8 years (3.0; 95% CI 2.3-3.9). CP prevalence in these two migration strata was similar by sex and race/ethnicity. CP birth prevalence of 8-year-olds in Atlanta in 2000 was 2.0 (95% CI 1.6-2.5) per 1000 live births in 1992.
  
  
  CONCLUSIONS
  The authors found no evidence to support the hypothesis that differential in-migration explained higher period than birth prevalence of CP in Atlanta. Comparability of CP prevalence across geographic areas will be enhanced if future studies report both period and birth prevalence.
authors.affiliation: Developmental Disabilities Branch, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Kim
authors.initials: K
authors.lastname: Van Naarden Braun
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Maenner
authors.forename: Deborah
authors.initials: D
authors.lastname: Christensen
authors.forename: Nancy S
authors.initials: NS
authors.lastname: Doernberg
authors.forename: Maureen S
authors.initials: MS
authors.lastname: Durkin
authors.forename: Russell S
authors.initials: RS
authors.lastname: Kirby
authors.forename: Marshalyn
authors.initials: M
authors.lastname: Yeargin-Allsopp
mesh_terms: D001315:Australia / Q000453:epidemiology; D002547:Cerebral Palsy / Q000453:epidemiology* / Q000208:ethnology; D002648:Child; D006233:Persons with Disabilities / Q000706:statistics & numerical data*; D005060:Europe / Q000453:epidemiology; D005260:Female; D005845:Georgia / Q000453:epidemiology; D063426:Human Migration; D006801:Humans; D008297:Male; D011159:Population Surveillance / Q000379:methods; D015995:Prevalence; D014481:United States / Q000453:epidemiology