title: An intergenerational and lifecourse study of health and mortality risk in parents of the 1958 birth cohort: (II) mortality rates and study representativeness.
abstract: OBJECTIVE
  We recently traced and flagged parents for the participants in the National Child Development Survey (NCDS, 1958 cohort). This paper evaluates the representativeness of the study population and assesses our success in identifying the biological parents.
  
  
  METHODS
  Intergenerational cohort study.
  
  
  METHODS
  Parents for participants in the NCDS (born 1 week in March 1958) were traced and flagged for mortality follow-up (14 334 fathers, 15 076 mothers). Standardized mortality rates (SMRs) were calculated using data from England, Scotland and Wales during corresponding time periods.
  
  
  RESULTS
  By 31 December 2003, 6808 fathers and 4148 mothers (born 1890-1943) had died (569 918 and 645 354 years of follow-up, respectively). The overall mortality rate in this parent population was lower compared with the age-, gender-, period- and area-standardized reference rates (SMRs of 83 for fathers and 86 for mothers). Mortality rates for biological parents were higher if cohort members had had non-biological parent figures during the childhood surveys (SMRs of 135 for fathers and 374 for mothers). Parental smoking (in 1974) was strongly associated with lung cancer mortality among biological parents [HR 6.1, 95% confidence intervals (CI) 4.6-8.1 for fathers; HR 15.0, 95% CI 9.7-23 for mothers) but not among non-biological parents (HR 2.0, 95% CI 0.8-5.5; HR 1.8, 95% CI 0.4-7.9, respectively) which demonstrates that the tracing of the biological parents had been successful.
  
  
  CONCLUSIONS
  Mortality is markedly reduced in a cohort of parents compared with the general population. The validity of identification of biological parents is demonstrated by the strong association between smoking and lung cancer.
authors.affiliation: Centre for Paediatric Epidemiology and Biostatistics, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK. e.hypponen@ich.ucl.ac.uk
authors.forename: Elina
authors.initials: E
authors.lastname: Hyppönen
authors.forename: George
authors.initials: G
authors.lastname: Davey Smith
authors.forename: Peter
authors.initials: P
authors.lastname: Shepherd
authors.forename: Chris
authors.initials: C
authors.lastname: Power
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002657:Child Development; D015331:Cohort Studies; D004739:England / Q000453:epidemiology; D005192:Family Health; D005220:Fathers / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000453:epidemiology / Q000401:mortality; D008297:Male; D008875:Middle Aged; D009026:Mortality / Q000639:trends*; D009035:Mothers / Q000706:statistics & numerical data*; D010287:Parent-Child Relations; D011159:Population Surveillance / Q000379:methods*; D016016:Proportional Hazards Models; D012042:Registries; D015203:Reproducibility of Results; D012606:Scotland / Q000453:epidemiology; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology; D014852:Wales / Q000453:epidemiology