Familial aggregation of myopia in the Tehran eye study: estimation of the sibling and parent–offspring recurrence risk ratios
- Akbar Fotouhi1,
- Arash Etemadi2,
- Hassan Hashemi3,
- Hojjat Zeraati4,
- Joan E Bailey-Wilson5,
- Kazem Mohammad6
- 1Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
- 2Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences
- 3Farabi Eye Hospital, School of Medicine, Tehran University of Medical Sciences, Tehran, and Noor Vision Correction Centre, Tehran
- 4Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences
- 5Inherited Disease Research Branch, National Human Genome Research Institute, Baltimore, Maryland, USA
- 6Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences
- Dr Akbar Fotouhi, Epidemiology and Biostatistics Department, School of Public Health, Tehran University of Medical Sciences, Pursina St, Keshavarz Blvd, Tehran, Iran;
- Accepted 2 May 2007
- Published Online First 10 May 2007
Aim: 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 (λR) 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 (λR ranging from 2.09 to 3.86) and parent–offspring pairs (λR 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.
Competing interests: None declared.
generalised estimating equations
second order generalised estimating equations