Hemoglobin levels are associated with retinal vascular caliber in a middle-aged birth cohort

Abstract

Vascular and neural structures of the retina can be visualized non-invasively and used to predict ocular and systemic pathologies. We set out to evaluate the association of hemoglobin (Hb) levels within the national reference interval with retinal vascular caliber, optical coherence tomography (OCT) and visual field (VF) parameters in the Northern Finland 1966 Birth Cohort (n = 2319, 42.1% male, average age 47 years). The studied parameters were evaluated in Hb quintiles and multivariable linear regression models. The lowest Hb quintile of both sexes presented the narrowest central retinal vein equivalent (CRVE) and the healthiest cardiometabolic profile compared to the other Hb quintiles. In the regression models, CRVE associated positively with Hb levels in both sexes, (B_males = 0.068 [0.001; 0.135], B_females = 0.087 [0.033; 0.140]), after being adjusted for key cardiometabolic and inflammatory parameters, smoking status, and fellow vessel caliber. No statistically significant associations of Hb levels with central retinal artery equivalent, OCT or VF parameters were detected. In conclusion, Hb levels were positively and specifically associated with CRVE, indicating that Hb levels are an independent factor affecting CRVE and the effect is in parallel with established risk factors for cardiometabolic diseases.

Figure 1

Retinal vascular caliber parameters in sex-specific Hb quintiles. CRAE (A, B), CRVE (C, D) and AVR (E, F) in Hb quintiles for males (white dot; A, C, E) and females (black dot; B, D, F). The values are mean with (SD). P is given for comparison over the Hb quintiles in one-way ANOVA. Q, quintile; B-Hb, blood hemoglobin; CRAE, central retinal artery equivalent; CRVE, central retinal vein equivalent; AVR, arteriovenous ratio.

Figure 2

Sex-specific effect sizes for association of Hb levels with ophthalmological parameters. Forest plot representing the effect sizes and their 95% CIs for Hb levels and ophthalmological parameters in males (A) and females (B). The CIs and effect sizes represent change in standardized variables. Model 1 (presented in black) represents unadjusted linear regression. Model 2 (presented in red) is a linear regression model adjusted for smoking, BP and refractive error. CRAE, central retinal artery equivalent; CRVE, central retinal vein equivalent; AVR, arteriovenous ratio; RNFL, retinal nerve fiber layer; th, thickness; V, volume; MD, mean deviation; PSD, pattern standard deviation.

Figure 3

Sex-specific effect sizes for association of Hb levels with retinal vascular parameters in multivariable linear regression models. Forest plot representing the effect sizes and their 95% CIs for Hb levels and selected ophthalmological parameters in males (A) and females (B). The CIs and effect sizes represent change in standardized variables. Model 3 (presented in black) is adjusted for smoking, blood pressure, refractive error, BMI, HOMA-IR, Matsuda index, hsCRP, LDL cholesterol, HDL cholesterol, triglycerides, and albumin levels, and Model 4 (presented in red), additionally for fellow vessel caliber. CRAE, central retinal artery equivalent; CRVE, central retinal vein equivalent; AVR, arteriovenous ratio.