Heritability of Retinal Vessel Diameters and Blood Pressure: A Twin Study

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Abstract
To assess the relative influence of genetic and environmental effects on retinal vessel diameters and blood pressure in healthy adults, as well as the possible genetic connection between these two characteristics. In 55 monozygotic and 50 dizygotic same-sex healthy twin pairs, aged 20 to 46 years, interpolated diameter estimates for the central retinal artery (CRAE), the central retinal vein (CRVE), and the artery-to-vein diameter ratio (AVR) were assessed by analysis of digital gray-scale fundus photographs of right eyes. The heritability was 70% (95% CI: 54%-80%) for CRAE, 83% (95% CI: 73%-89%) for CRVE, and 61% (95% CI: 44%-73%) for mean arterial blood pressure (MABP). Retinal artery diameter decreased with increasing age and increasing arterial blood pressure. Mean vessel diameters in the population were 165.8 +/- 14.9 microm for CRAE, 246.2 +/- 17.7 microm for CRVE, and 0.67 +/- 0.05 microm for AVR. No significant influence on artery or vein diameters was found for gender, smoking, body mass index (BMI), total cholesterol, fasting blood glucose, or 2-hour oral glucose tolerance test values. In healthy young adults with normal blood pressure and blood glucose, variations in retinal blood vessel diameters and blood pressure were predominantly attributable to genetic effects. A genetic influence may have a role in individual susceptibility to hypertension and other vascular diseases. The results suggest that retinal vessel diameters and the possible associated variations in risk of vascular disease are primarily genetic characteristics.