title: A twin study of erectile dysfunction.
abstract: BACKGROUND
  The extent of genetic influence on erectile dysfunction (ED) is unknown. This study determines the contribution of heredity to ED in a sample of middle-aged men.
  
  
  METHODS
  A classical twin study was conducted in the Vietnam Era Twin Registry, a national sample of male-male pairs (mean birth year, 1949) who served on active duty during the Vietnam era (1965-1975). A 1999 male health survey was completed by 890 monozygotic (MZ) and 619 dizygotic (DZ) pairs. The prevalence and heritability of 2 self-report indicators of ED, difficulty in having an erection and in maintaining an erection, are estimated.
  
  
  RESULTS
  The prevalence of difficulty in having an erection is 23.3% and in maintaining an erection is 26.7%. Twin correlations for dysfunction in having an erection are 0.35 (95% confidence interval [CI], 0.28-0.41) in MZ and 0.17 (95% CI, 0.09-0.27) in DZ pairs. For dysfunction in maintaining an erection, the twin correlations in MZ and DZ pairs are 0.39 (95% CI, 0.32-0.45) and 0.18 (95% CI, 0.09-0.27), respectively. The estimated heritability of liability for dysfunction in having an erection is 35% and in maintaining an erection is 42%. The heritable influence on ED remained significant after adjustment for ED risk factors.
  
  
  CONCLUSIONS
  The present study demonstrates an ED-specific genetic component that is independent of genetic influences from numerous ED risk factors. The results suggest that future molecular genetic studies to identify ED-related polymorphisms are warranted.
authors.affiliation: Vietnam Era Twin Registry/Seattle Epidemiologic Research and Information Center, VA Puget Sound Health Care System, Seattle, WA 98108, USA.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Fischer
authors.forename: Mary Ellen
authors.initials: ME
authors.lastname: Vitek
authors.forename: Don
authors.initials: D
authors.lastname: Hedeker
authors.forename: William G
authors.initials: WG
authors.lastname: Henderson
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Jacobsen
authors.forename: Jack
authors.initials: J
authors.lastname: Goldberg
mesh_terms: D000328:Adult; D000367:Age Factors; D007172:Erectile Dysfunction / Q000453:epidemiology* / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008889:Military Personnel; D015995:Prevalence; D012042:Registries; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014427:Twins / Q000235:genetics*; D014481:United States