title: Epidemiologic characteristics of intraocular pressure in the Korean and Mongolian populations: the Healthy Twin and the GENDISCAN study.
abstract: OBJECTIVE
  The purpose of this study was to demonstrate a negative association between intraocular pressure (IOP) and age in 2 Asian populations. In addition, we evaluated genetic and nongenetic factors associated with IOP.
  
  
  METHODS
  Family-based cohort study.
  
  
  METHODS
  Study subjects >10 years of age from one Korean (The Healthy Twin; n = 1431) and 2 Mongolian populations (The GENDISCAN; n = 859 and 806) with IOP values.
  
  
  METHODS
  The IOP values were measured with a noncontact tonometer. Each participant received a standard health examination and received questionnaires, which include candidate risk factors on IOP. Mixed models were used to identify risk factors for IOP. Variance-component methods were applied to estimate the heritability of IOP.
  
  
  METHODS
  The negative trend of IOP with aging and evaluation of impact of genetic and nongenetic components on IOP.
  
  
  RESULTS
  The mean ages were 43.6, 34.1, and 36.3 years for the Korean, Orhontuul, and Dashbalbar populations, respectively. The mean IOPs were 14.4 mmHg (95% confidence interval [CI], 14.3-14.6) in the Koreans and 14.1 mmHg (95% CI, 13.9-14.3) and 12.6 mmHg (95% CI, 12.4-12.9) in the Orhontuul and Dashbalbar populations, respectively. In the 3 populations, the IOP decreased as age increased. We replicated an association of systolic blood pressure (SBP) with IOP. In addition, components of the metabolic syndrome (MS), such as plasma glucose, lipid level, and body mass index, showed positive associations with IOP, after adjusting for age and SBP. The IOP also had strong genetic contributions in all populations (heritability, 0.47-0.51).
  
  
  CONCLUSIONS
  Negative associations between age and IOP were observed in all 3 populations, which cannot be explained by the increasing prevalence of myopia in the younger generation. The different age trend in IOP may in part be responsible for differences in the prevalence of glaucoma subtypes. Our findings suggest that associations between IOP and MS components were independent of established risk factors such as SBP or age. In addition, the importance of inherited risks requires further genetic dissection of IOP determinants for biological understandings of underlying pathophysiology.
authors.affiliation: Department of Epidemiology and Institute of Environment and Health, School of Public Health, Seoul National University, Seoul, Korea.
authors.forename: Mi Kyeong
authors.initials: MK
authors.lastname: Lee
authors.forename: Sung-Il
authors.initials: SI
authors.lastname: Cho
authors.forename: Ho
authors.initials: H
authors.lastname: Kim
authors.forename: Yun-Mi
authors.initials: YM
authors.lastname: Song
authors.forename: Kayoung
authors.initials: K
authors.lastname: Lee
authors.forename: Jong-Il
authors.initials: JI
authors.lastname: Kim
authors.forename: Dong-Myung
authors.initials: DM
authors.lastname: Kim
authors.forename: Tae-Young
authors.initials: TY
authors.lastname: Chung
authors.forename: Youn Sic
authors.initials: YS
authors.lastname: Kim
authors.forename: Jeong-Sun
authors.initials: JS
authors.lastname: Seo
authors.forename: Don-Il
authors.initials: DI
authors.lastname: Ham
authors.forename: Joohon
authors.initials: J
authors.lastname: Sung
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D044466:Asian People / Q000235:genetics; D001824:Body Constitution; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000235:genetics* / Q000502:physiology; D007723:Korea / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D008986:Mongolia / Q000453:epidemiology; D009216:Myopia / Q000453:epidemiology; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014065:Tonometry, Ocular; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*