Longitudinal Changes in Blood Pressure and Retinal Vasculature: The Singapore Malay Eye Study

Abstract

Purpose: Retinal vascular changes, reflecting more generalized microcirculatory alternations, are closely associated with blood pressure (BP) and risk of hypertension. We examined the association between longitudinal changes in retinal vasculature measures and BP in a cohort of Singapore Malays.

Methods: The Singapore Malay Eye Study examined 3280 persons of Malay ethnicity aged between 40 to 80 years at baseline (2004-2006) and a 6-year follow-up is currently being conducted (2010-2013). Identical retinal vascular and BP parameters were measured at both visits following a standardized protocol. Retinal vascular indices including vessel caliber, bifurcation, tortuosity and fractal dimension, were measured using a computer-assisted program (Singapore I Vessel Assessment [SIVA]). The percentage changes in retinal vascular parameters, systolic (SBP), diastolic (DBP) and mean arterial blood pressure (MABP) were defined as the ratio of difference between first and second visits relative to the first visit. Participants were classified as having normal BP or pre-hypertension, mild hypertension or severe hypertension.

Results: Among the 1507 participants who have returned for follow-up examinations, 88 participants who had normal BP status at baseline were selected for analysis. Among these, 38 (43.2%) developed incident mild or severe hypertension. The mean (standard deviation [SD], interquartile range [IQR]) changes in SBP, DBP and MABP were 5.75% (10.95, -3.38% to 14.45%), 4.21% (10.49, IQR -2.98% to 9.85%) and 4.85% (9.12, IQR -2.39% to 11.76%), respectively. In multiple regression analysis, after adjusting for age and gender; each 10% decrease in arteriolar caliber change and each 10% increase in retinal arteriolar branching coefficient change was borderline associated with a 2.68% (p =0.050) increase and a 1.19% (p =0.050) increase in MABP change, respectively. Each 10% decrease both in total fractal dimension change and in arteriolar fractal dimension change was associated with a 10.27% increase (p=0.039) and a 7.66% (p =0.023) increase in DBP change, respectively. No significant associations were found with other retinal vascular parameters.

Conclusions: Longitudinal changes in retinal arteriolar caliber, bifurcation and fractal dimension are correlated with changes in BP, providing further evidence that retinal vascular parameters track BP changes over time.

Keywords: 688 retina • 463 clinical (human) or epidemiologic studies: prevalence/incidence • 464 clinical (human) or epidemiologic studies: risk factor assessment