title: The heritability of leucocyte telomere length dynamics.
abstract: BACKGROUND
  Leucocyte telomere length (LTL) is a complex trait associated with ageing and longevity. LTL dynamics are defined by LTL and its age-dependent attrition. Strong, but indirect evidence suggests that LTL at birth and its attrition during childhood largely explains interindividual LTL variation among adults. A number of studies have estimated the heritability of LTL, but none has assessed the heritability of age-dependent LTL attrition.
  
  
  METHODS
  We examined the heritability of LTL dynamics based on a longitudinal evaluation (an average follow-up of 12 years) in 355 monozygotic and 297 dizygotic same-sex twins (aged 19-64 years at baseline).
  
  
  RESULTS
  Heritability of LTL at baseline was estimated at 64% (95% CI 39% to 83%) with 22% (95% CI 6% to 49%) of shared environmental effects. Heritability of age-dependent LTL attrition rate was estimated at 28% (95% CI 16% to 44%). Individually unique environmental factors, estimated at 72% (95% CI 56% to 84%) affected LTL attrition rate with no indication of shared environmental effects.
  
  
  CONCLUSIONS
  This is the first study that estimated heritability of LTL and also its age-dependent attrition. As LTL attrition is much slower in adults than in children and given that having a long or a short LTL is largely determined before adulthood, our findings suggest that heritability and early life environment are the main determinants of LTL throughout the human life course. Thus, insights into factors that influence LTL at birth and its dynamics during childhood are crucial for understanding the role of telomere genetics in human ageing and longevity.
authors.affiliation: Department of Epidemiology, Biostatistics and Biodemography, Institute of Public Health, University of Southern Denmark, Odense, Denmark The Danish Twin Registry, University of Southern Denmark, Odense, Denmark.
authors.forename: Jacob B
authors.initials: JB
authors.lastname: Hjelmborg
authors.affiliation: Department of Environmental Medicine, Institute of Public Health, University of Southern Denmark, Odense, Denmark.
authors.forename: Christine
authors.initials: C
authors.lastname: Dalgård
authors.affiliation: Department of Epidemiology, Biostatistics and Biodemography, Institute of Public Health, University of Southern Denmark, Odense, Denmark The Danish Twin Registry, University of Southern Denmark, Odense, Denmark.
authors.forename: Soren
authors.initials: S
authors.lastname: Möller
authors.affiliation: Department of Epidemiology, Biostatistics and Biodemography, Institute of Public Health, University of Southern Denmark, Odense, Denmark The Danish Twin Registry, University of Southern Denmark, Odense, Denmark.
authors.forename: Troels
authors.initials: T
authors.lastname: Steenstrup
authors.affiliation: Center of Human Development and Aging, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey, USA.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kimura
authors.affiliation: Department of Epidemiology, Biostatistics and Biodemography, Institute of Public Health, University of Southern Denmark, Odense, Denmark The Danish Twin Registry, University of Southern Denmark, Odense, Denmark Department of Clinical Genetics, Odense University Hospital, Odense, Denmark Department of Clinical Biochemistry and Pharmacology, Odense University Hospital, Odense, Denmark.
authors.forename: Kaare
authors.initials: K
authors.lastname: Christensen
authors.affiliation: Institute of Regional Health Services Research, University of Southern Denmark and Odense Patient data Explorative Network (OPEN), Odense University Hospital, Odense, Denmark.
authors.forename: Kirsten O
authors.initials: KO
authors.lastname: Kyvik
authors.affiliation: Center of Human Development and Aging, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey, USA.
authors.forename: Abraham
authors.initials: A
authors.lastname: Aviv
mesh_terms: D000328:Adult; D001699:Biometry; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007962:Leukocytes; D008297:Male; D008875:Middle Aged; D012042:Registries; D016615:Telomere / Q000235:genetics* / Q000378:metabolism*; D059505:Telomere Homeostasis; D014427:Twins / Q000235:genetics; D055815:Young Adult