title: Familial aggregation of myopia in the Tehran eye study: estimation of the sibling and parent offspring recurrence risk ratios.
abstract: OBJECTIVE
  To determine the potential influence of genetic factors on the prevalence of myopia in Tehran.
  
  
  METHODS
  Of 6497 citizens of Tehran sampled from 160 clusters using stratified random cluster sampling, 4565 (70.3%) participated in the study and were referred to a clinic for an extensive eye examination and interview. These were from 1259 nuclear families with the average size of 3.6. Refraction data obtained from 3321 participants aged 16 years and over are presented. Three definitions of myopia, as the spherical equivalent of -0.5, -1, and -2 diopters or less, were used. Familial aggregation of myopia was evaluated with odds ratios and recurrence risk ratios (lambda(R)) using a multiple logistic regression with generalised estimating equations (GEE), adjusted for age, sex, height, and education.
  
  
  RESULTS
  Multivariate analyses showed a strong familial aggregation of myopia among siblings (lambda(R) ranging from 2.09 to 3.86) and parent-offspring pairs (lambda(R) from 1.82 to 3.81) adjusted for age, sex, height, and education. The aggregation increased with higher myopia thresholds and with the use of cycloplegic refraction. The odds ratios for spouse pairs were not significantly different from 1.0. The association of myopia with sex, height, and education (and not age) remained significant in the final GEE2 model.
  
  
  CONCLUSIONS
  The findings indicate a relatively high degree of familial aggregation of myopia in the Tehran population, independent of age, sex, height, and education. This residual aggregation may be a result of heredity or of an unmeasured common environmental effect.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. afotouhi@tums.ac.ir
authors.forename: Akbar
authors.initials: A
authors.lastname: Fotouhi
authors.forename: Arash
authors.initials: A
authors.lastname: Etemadi
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.forename: Hojjat
authors.initials: H
authors.lastname: Zeraati
authors.forename: Joan E
authors.initials: JE
authors.lastname: Bailey-Wilson
authors.forename: Kazem
authors.initials: K
authors.lastname: Mohammad
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001827:Body Height; D004522:Educational Status; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007492:Iran / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000453:epidemiology / Q000235:genetics*; D017678:Sex Distribution