title: Heritabilities of intraocular pressure in the population of Korea: the Korean National Health and Nutrition Examination Survey 2008-2009.
abstract: OBJECTIVE
  Intraocular pressure (IOP) is the principal modifiable risk factor for the progression of primary open-angle glaucoma. Studies that have measured the IOP directly in large numbers of matched parent-offspring pairs are limited in Asian populations.
  
  
  OBJECTIVE
  To compare IOPs in parents and their offspring in Korea.
  
  
  METHODS
  Family-based cohort study examining data from the Korean National Health and Nutrition Examination Survey conducted between 2008 and 2009. Data were obtained from 9700 participants from Korea.
  
  
  METHODS
  Familial correlations for IOP were calculated in different types of relative pairs. Variance component methods were used to obtain heritability estimates. The individuals were stratified into 2 groups (those with and those without an IOP of ≥ 19 mm Hg; ie, high IOP group and nonhigh IOP group) based on the mean plus 2 SD IOP value of the entire study population. We evaluated the impact of parents' high IOP on offspring's high IOP. The relationship between parental systemic disease and high IOP in their offspring was also investigated.
  
  
  RESULTS
  The mean (SD) IOPs in the right and left eyes were 13.90 (2.74) and 13.89 (2.74) mm Hg, respectively. Correlation coefficient estimates between parent-offspring pairs, sibling pairs, and spouse pairs for IOP were significant as 0.19, 0.31, and 0.29 (P < .001, P = .001, and P < .001, respectively). The total variance of the phenotype under study was explained by 2 sources of variation, additive genetic (36% [95% CI, 32%-40%]) and unique environment (64% [95% CI, 60%-68%]). The risks of high IOP conferred by parents' high IOP were found to be significant for participants whose parents had high IOP (odds ratio, 9.76 [95% CI, 2.16-44.12]). In this study, high IOP was not associated with parental diabetes mellitus, hypertension, obesity, or metabolic syndrome.
  
  
  CONCLUSIONS
  Intraocular pressure showed a significant heritable tendency from parents to their offspring with a heritability estimate of 0.36 in Asian populations. The risk of high IOP was significantly increased in participants whose parents had high IOP. This has potential implications for the screening of family members of patients with ocular hypertension and glaucoma.
authors.affiliation: Department of Ophthalmology and Inha Vision Science Laboratory, Inha University School of Medicine, Incheon, Korea.
authors.forename: Na Rae
authors.initials: NR
authors.lastname: Kim
authors.affiliation: Clinical Trial Center, Inha University Hospital, Incheon, Korea.
authors.forename: Hyun Ju
authors.initials: HJ
authors.lastname: Park
authors.affiliation: Department of Clinical Research, Inha University School of Medicine, Incheon, Korea.
authors.forename: Young Ju
authors.initials: YJ
authors.lastname: Suh
authors.affiliation: Department of Ophthalmology and Inha Vision Science Laboratory, Inha University School of Medicine, Incheon, Korea.
authors.forename: Hee Seung
authors.initials: HS
authors.lastname: Chin
authors.affiliation: Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Chan Yun
authors.initials: CY
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People / Q000235:genetics*; D001824:Body Constitution; D018450:Disease Progression; D005260:Female; D005902:Glaucoma, Open-Angle / Q000208:ethnology / Q000235:genetics*; D006801:Humans; D007429:Intraocular Pressure / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D010641:Phenotype; D019655:Quantitative Trait, Heritable; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D014065:Tonometry, Ocular; D055815:Young Adult