Serum ferritin and hemoglobin are independently associated with wider retinal venular caliber: the Tromsø Study 2001-2008.

Purpose: To investigate if markers of iron body stores and hemoglobin are associated with retinal vascular caliber.

Methods: This was a population-based study including 2993 participants of the fifth and sixth surveys of the Tromsø Study in Norway, conducted in 2001-2002 and 2007-2008. The association between levels of s-ferritin, transferrin saturation, and hemoglobin in the fifth survey and retinal vascular caliber in the sixth survey was assessed by multivariable linear regression models.

Results: Men had higher levels of hemoglobin and s-ferritin than women. Hemoglobin was associated with wider retinal venules in both men and women (mean difference between highest compared to lowest sex-specific quartile: men 5.99 μm, P = 0.001; women 7.28 μm, P < 0.001). S-ferritin was associated with wider retinal venules in men but not women, independent of traditional risk factors (mean difference between highest compared to lowest sex-specific quartile: men 4.21 μm, P = 0.013; women -0.21 μm, P = 0.89). The association in men was attenuated, but still significant, with adjustment for hemoglobin. S-ferritin and level of hemoglobin were not associated with arteriolar caliber in either sex. Transferrin saturation was not associated with retinal vascular caliber.

Conclusions: Level of hemoglobin was associated with wider retinal venules in both sexes while s-ferritin was associated with wider retinal venular caliber only in men. Men have higher levels of stored iron, and this may underlie the observed sex difference in the association between s-ferritin and retinal vascular caliber.