title: Perceived age as clinically useful biomarker of ageing: cohort study.
abstract: OBJECTIVE
  To determine whether perceived age correlates with survival and important age related phenotypes.
  
  
  METHODS
  Follow-up study, with survival of twins determined up to January 2008, by which time 675 (37%) had died.
  
  
  METHODS
  Population based twin cohort in Denmark.
  
  
  METHODS
  20 nurses, 10 young men, and 11 older women (assessors); 1826 twins aged >or=70.
  
  
  METHODS
  Assessors: perceived age of twins from photographs. Twins: physical and cognitive tests and molecular biomarker of ageing (leucocyte telomere length).
  
  
  RESULTS
  For all three groups of assessors, perceived age was significantly associated with survival, even after adjustment for chronological age, sex, and rearing environment. Perceived age was still significantly associated with survival after further adjustment for physical and cognitive functioning. The likelihood that the older looking twin of the pair died first increased with increasing discordance in perceived age within the twin pair-that is, the bigger the difference in perceived age within the pair, the more likely that the older looking twin died first. Twin analyses suggested that common genetic factors influence both perceived age and survival. Perceived age, controlled for chronological age and sex, also correlated significantly with physical and cognitive functioning as well as with leucocyte telomere length.
  
  
  CONCLUSIONS
  Perceived age-which is widely used by clinicians as a general indication of a patient's health-is a robust biomarker of ageing that predicts survival among those aged >or=70 and correlates with important functional and molecular ageing phenotypes.
authors.affiliation: Danish Twin Registry and Danish Aging Research Center, Institute of Public Health, University of Southern Denmark, DK-5000 Odense C, Denmark. kchristensen@health.sdu.dk
authors.forename: Kaare
authors.initials: K
authors.lastname: Christensen
authors.forename: Mikael
authors.initials: M
authors.lastname: Thinggaard
authors.forename: Matt
authors.initials: M
authors.lastname: McGue
authors.forename: Helle
authors.initials: H
authors.lastname: Rexbye
authors.forename: Jacob V B
authors.initials: JV
authors.lastname: Hjelmborg
authors.forename: Abraham
authors.initials: A
authors.lastname: Aviv
authors.forename: David
authors.initials: D
authors.lastname: Gunn
authors.forename: Frans
authors.initials: F
authors.lastname: van der Ouderaa
authors.forename: James W
authors.initials: JW
authors.lastname: Vaupel
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000523:psychology*; D001294:Attitude to Health; D003071:Cognition / Q000502:physiology; D003718:Denmark / Q000453:epidemiology; D005260:Female; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D007962:Leukocytes / Q000166:cytology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009026:Mortality; D010465:Perception; D010641:Phenotype; D012307:Risk Factors; D016019:Survival Analysis; D016615:Telomere