Retinal Vasculature Reactivity During Flicker Light Provocation, Cardiac Stress and Stroke Risk in Africans: The SABPA Study
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Structural and functional similarities exist between the retinal, cerebral and, as previously suggested, the coronary microvasculature. Retinal microvascular structure and functionality (in response to flicker-light-induced-provocation (FLIP)) may relate to coronary artery disease risk and possible stroke risk. We investigated associations between retinal vessel structure, functionality and cardiac stress markers (cardiac troponin T [cTnT], amino-terminal B-type natriuretic peptide [NT-proBNP]) to translate these retina–heart relationships to stroke risk. We included 317 African and Caucasian teachers’ (aged 23–68 years), who participated in the Sympathetic Activity and Ambulatory Blood Pressure in Africans (SABPA) study. Fasting plasma and serum samples for cTnT and NT-proBNP were collected. Retinal vascular calibres were quantified from fundus images and dynamic retinal vessel calibre responses during FLIP. The University of California stroke risk score was applied to assess sub-clinical 10-year stroke risk. cTnT levels were similar in Africans and Caucasians, whereas NT-proBNP levels were lower in Africans. In Africans, a reduced arteriolar calibre and attenuated arteriolar dilation during FLIP was associated with higher cTnT (p < 0.01). Their larger retinal–venular calibre (p < 0.02) and attenuated arteriolar dilation during FLIP (p < 0.05) were associated with lower NT-proBNP. Again, exclusively in Africans, increased cardiac stress, wider venular calibres and retinal arteriovenous nicking predicted an increased 10-year stroke risk with odds ratios of 1.57 (95% CI, 1.34; 1.68, p = 0.031), 1.51 (95% CI, 1.26; 1.59, p = 0.002), 1.10 (95% CI, 0.94; 2.85, p = 0.002) and 1.06 (95% CI 0.83; 1.56, p = 0.052), respectively. None of these associations were evident in the Caucasian group. Investigating the retinal vasculature may serve as a tool to approximate sub-clinical coronary and cerebral microvasculature damage or dysfunction. These cardiac stress–retinal associations additionally predicted a greater stroke risk in the SABPA African cohort. Observable changes in the retinal vasculature may serve as markers for the identification and prediction of cardio-systemic and cerebral vascular morbidities and risks, thereby establishing a brain-heart link.
KeywordsRetina Dynamic retinal vessel responses Flicker-light-induced-provocation (FLIP) NT-proBNP cTnT Stroke Ethnicity
Area under the curve
Dynamic vessel analyses
Cardiac troponin T
Amino-terminal pro-B-type natriuretic peptide
The present study was partially funded by the National Research Foundation, South African Medical Research Council, ROCHE Diagnostics, North-West University (Potchefstroom Campus), North-West Department of Education South Africa as well as the Metabolic Syndrome institute, France.
Compliance with Ethical Standards
The SABPA study obtained ethical approval from the Health Research Ethics Committee (HREC) of the NWU and extended approval was granted for the second phase (ethics number: NWU-00036-07-S6). Written informed consent was obtained from all volunteers prior to participation. All procedures and objectives were explained to the participants prior to their recruitment and adhered to the applicable institutional guidelines and terms, as stated by the Declaration of Helsinki (2004). Please also refer to uploaded SABPA Protocol article.
Conflict of Interest
The authors declare that they have no conflict of interest.
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