title: Increased risk of type 2 diabetes in elderly twins.
abstract: OBJECTIVE
  Genetic susceptibility, low birth weight (LBW), and aging are key etiological factors in the development of type 2 diabetes. LBW is common among twins. It is unknown whether twin status per se is associated with risk of type 2 diabetes, and valid concordance rates of type 2 diabetes in twins on a lifetime perspective are lacking.
  
  
  METHODS
  A clinical study was done on a population-based cohort of same-sex elderly monozygotic (MZ) and dizygotic (DZ) twins (n = 297) and singleton control subjects (C) (n = 71) including measures of anthropometry and glucose tolerance. In addition, type 2 diabetes incidence cases in twins (n = 626) and singletons (n = 553) were identified through the National Diabetes Register.
  
  
  RESULTS
  Twins were more abdominally obese, insulin resistant, and glucose intolerant, as evidenced by a higher A1C (%) (means +/- SD) (MZ: 6.0 +/- 1.0, DZ: 5.8 +/- 0.7, C: 5.6 +/- 0.3, P = 0.004) and 120-min post-oral glucose tolerance test plasma glucose levels (in mmol/l) (MZ: 8.6 +/- 4.6, DZ: 8.4 +/- 3.9, C: 6.8 +/- 2.4, P = 0.003) compared with singletons. Importantly, twins had a higher prevalence of type 2 diabetes (MZ: 17.5% [95% CI 14.4-20.6], DZ: 15.7% [13.1-18.3], C: 5.6% [3.0-8.2], P = 0.03) together with a 60% higher incidence rate of type 2 diabetes compared with singletons. Cumulative concordance rates of type 2 diabetes to the age of 84 years were similar among elderly MZ (0.76 [0.68-0.84]) and DZ (0.71 [0.63-0.78]) twins.
  
  
  CONCLUSIONS
  Twin status per se is associated with abdominal obesity, insulin resistance, and increased prevalence of type 2 diabetes in elderly twins. The data support a quantitatively significant impact of the fetal environment as opposed to genetics on risk of type 2 diabetes.
authors.affiliation: Steno Diabetes Center, Gentofte, Denmark. pepn@novonordisk.com
authors.forename: Pernille
authors.initials: P
authors.lastname: Poulsen
authors.forename: Louise G
authors.initials: LG
authors.lastname: Grunnet
authors.forename: Kasper
authors.initials: K
authors.lastname: Pilgaard
authors.forename: Heidi
authors.initials: H
authors.lastname: Storgaard
authors.forename: Amra
authors.initials: A
authors.lastname: Alibegovic
authors.forename: Mette P
authors.initials: MP
authors.lastname: Sonne
authors.forename: Bendix
authors.initials: B
authors.lastname: Carstensen
authors.forename: Henning
authors.initials: H
authors.lastname: Beck-Nielsen
authors.forename: Allan
authors.initials: A
authors.lastname: Vaag