title: Mortality among twins after age 6: fetal origins hypothesis versus twin method.
abstract: OBJECTIVE
  To test the validity of the fetal origins hypothesis and the classic twin method.
  
  
  METHODS
  Follow up study of pairs of same sex twins in which both twins survived to age 6.
  
  
  METHODS
  Denmark.
  
  
  METHODS
  8495 twin individuals born 1870-1900, followed through to 31 December 1991.
  
  
  METHODS
  Mortality calculated on a cohort basis.
  
  
  RESULTS
  Mortality among twins and the general population was not significantly different except among females aged 60-89, in whom mortality among twins was 1.14 times (SE 0.03) higher than in the general population. Mortality among female dizygotic twins was 1.77 times (0.18) higher than among monozygotic twins at age 30-59. Otherwise, mortality for monozygotic and dizygotic twins did not consistently differ after age 6.
  
  
  CONCLUSIONS
  According to the fetal origins hypothesis the risk of adult morbidity and mortality is heightened by retardation in intrauterine growth. Twins, and in particular monozygotic twins, experience growth retardation in utero. The findings in the present study suggest that the fetal origins hypothesis is not true for the retardation in intrauterine growth experienced by twins. Furthermore, the data are inconsistent with the underlying assumption of a recent claim that the classic twin method is invalid for studies of adult diseases. The present study is, however, based on the one third of all pairs of twins in which both twins survived to age 6. The possible impact of this selection can be evaluated in future studies of cohorts of younger twins with lower perinatal and infant mortality.
authors.affiliation: Odense University Medical School, Denmark.
authors.forename: K
authors.initials: K
authors.lastname: Christensen
authors.forename: J W
authors.initials: JW
authors.lastname: Vaupel
authors.forename: N V
authors.initials: NV
authors.lastname: Holm
authors.forename: A I
authors.initials: AI
authors.lastname: Yashin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D003718:Denmark / Q000453:epidemiology; D004200:Diseases in Twins / Q000209:etiology; D005260:Female; D005317:Fetal Growth Retardation / Q000150:complications*; D005500:Follow-Up Studies; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D009026:Mortality; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012737:Sex Factors; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic