title: Heritability of health-related quality of life: SF-12 summary scores in a population-based nationwide twin cohort.
abstract: OBJECTIVE
  The present study aims to estimate the relative importance of genetic and environmental factors for health-related quality of life (HRQL) measured by the 12-item Short-Form Health Survey (SF-12).
  
  
  METHODS
  The study was based on two Danish twin cohorts (46,417 twin individuals) originating from the nationwide, population-based Danish Twin Registry. The twins were approached by a mailed-out questionnaire in 2002. The questionnaire included the SF-12, information on demographic factors, and questions on a variety of specific diseases. Heritability of the SF-12 includes the physical component summary (PCS) and the mental component summary (MCS); and etiologically important variance components were estimated using multivariate biometric models. The respondents were stratified into six groups, based on age and sex.
  
  
  RESULTS
  A total of 33,794 (73%) individual twins responded to the survey. The SF-12 was completed by 29,619 individuals, which included 9,120 complete twin pairs. Overall, the best-fitting model explaining the variance of HRQL was the ACE model. The estimated heritability of the SF-12 was between 11% and 35%, whereas between 65% and 89% could be explained by unique environmental or stochastic factors in the different sex and age groups. The highest heritability was seen among older twins. In addition, the genetic correlation between MCS and PCS scores was low (0.07 and 0.23 for males and females, respectively) among younger and high (0.26 and 0.45 for males and females, respectively) in the oldest age group. Both the largest genetic influence on HRQL and the largest genetic overlap between the scores were seen in the oldest age group, which consisted of twins older than 55. The unique environmental correlation between MCS and PCS were generally negative.
  
  
  CONCLUSIONS
  The heritability of HRQL differs between different age groups. In general, most of the variance in the SF-12 summary components was determined by unique environmental factors.
authors.affiliation: Department of Biostatistics, University of Southern Denmark, Odense, Denmark.
authors.forename: Troels
authors.initials: T
authors.lastname: Steenstrup
authors.forename: Ole Birger
authors.initials: OB
authors.lastname: Pedersen
authors.forename: Jacob
authors.initials: J
authors.lastname: Hjelmborg
authors.forename: Axel
authors.initials: A
authors.lastname: Skytthe
authors.forename: Kirsten Ohm
authors.initials: KO
authors.lastname: Kyvik
mesh_terms: D000328:Adult; D000368:Aged; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D012042:Registries; D011795:Surveys and Questionnaires; D014427:Twins / Q000235:genetics*
references.citation: Eur J Epidemiol. 2001;17(11):991-9
references.pmid: 12380710
references.citation: Med Care. 1996 Mar;34(3):220-33
references.pmid: 8628042
references.citation: Twin Res. 2003 Aug;6(4):275-8
references.pmid: 14511432
references.citation: Behav Genet. 2009 Nov;39(6):605-15
references.pmid: 19728071
references.citation: Twin Res. 2002 Oct;5(5):352-7
references.pmid: 12537858
references.citation: Twin Res Hum Genet. 2010 Aug;13(4):322-9
references.pmid: 20707702
references.citation: Eur J Epidemiol. 2006;21(10):767-76
references.pmid: 17106761
references.citation: Aust N Z J Public Health. 2002 Dec;26(6):508-10
references.pmid: 12530792
references.citation: J Health Serv Res Policy. 1997 Jan;2(1):14-8
references.pmid: 10180648
references.citation: J Am Geriatr Soc. 2005 Jun;53(6):1002-7
references.pmid: 15935024
references.citation: Twin Res. 2001 Apr;4(2):73-80
references.pmid: 11665339
references.citation: Eur J Epidemiol. 2004;19(7):623-30
references.pmid: 15461193
references.citation: J Gerontol B Psychol Sci Soc Sci. 2001 May;56(3):S171-8
references.pmid: 11316842
references.citation: J Public Health Med. 2001 Sep;23(3):187-94
references.pmid: 11585190
references.citation: Health Serv Res. 2000 Dec;35(5 Pt 1):995-1010
references.pmid: 11130808
references.citation: Med Care. 2005 Nov;43(11):1147-54
references.pmid: 16224309
references.citation: J Clin Epidemiol. 1998 Nov;51(11):1171-8
references.pmid: 9817135
references.citation: Eur J Epidemiol. 2007;22(1):27-32
references.pmid: 17195050
references.citation: Behav Genet. 2009 Nov;39(6):597-604
references.pmid: 19618259
references.citation: Behav Genet. 2007 Mar;37(2):326-33
references.pmid: 16906466
references.citation: J Public Health Med. 1997 Jun;19(2):179-86
references.pmid: 9243433
references.citation: Int J Epidemiol. 1995 Jun;24(3):589-96
references.pmid: 7672901
references.citation: Twin Res Hum Genet. 2010 Apr;13(2):135-42
references.pmid: 20397744
references.citation: Psychiatry Res. 2007 Jul 30;152(1):63-71
references.pmid: 17395272
references.citation: Int J Epidemiol. 2007 Feb;36(1):77-83
references.pmid: 17251245