ArticlesRetinal microvascular abnormalities and incident stroke: the Atherosclerosis Risk in Communities Study
Introduction
Retinal microvascular abnormalities (such as microaneurysms and arteriovenous nicking) reflect arteriolar damage from hypertension and other processes. They have been suggested as markers for cerebral microvascular diseases, because the retinal and cerebral arterioles share common anatomy and physiology.1, 2, 3 Previous epidemiological studies that have investigated the association between retinal microvascular abnormalities and stroke have shown inconsistent results.4, 5, 6, 7, 8 This inconsistency may result partly from use of clinical ophthalmoscopy, a subjective and unreliable technique, to detect retinal lesions.9, 10, 11 Moreover, some of these data may not apply to contemporary populations, with lower blood pressures and infrequent signs of advanced retinopathy.12
Retinal photography was done for all participants at the third examination (1993-95) of the Atherosclerosis Risk in Communities (ARIC) study, a large populationbased cardiovascular study in middle-aged people. These photographs were graded for the presence of retinal microvascular characteristics on the basis of a standard protocol.13, 14, 15 The severity of retinal arteriolar narrowing was further quantified by measurement of individual arteriolar and venular calibres on highresolution digitised photographs.13 We have previously shown that this grading system is reliable13 and that retinal microvascular abnormalities are related to current blood pressure, to past blood pressure independently of current blood pressure,14 and to various markers of inflammation and endothelial dysfunction.15
In this study, we describe the relations between retinal microvascular abnormalities and incident stroke in the ARIC population.
Section snippets
Methods
Study population The ARIC study included a cohort of 15 792 women and men selected as probability samples of 45-64-year-old residents of four US communities: Forsyth County, NC; Jackson, MS (black people only); suburbs of Minneapolis, MN; and Washington County, MD.16 The initial participation rate was 46% in Jackson and about 65% in the other communities. Of the people examined at baseline, 14 346 (93% of survivors) returned for a second examination 3 years later and 12 887 (86% of survivors)
Procedures
Retinal photography and the grading procedure have been described in detail elsewhere.13, 14, 15 Briefly, after 5 min of dark adaptation, a 45° retinal photograph was taken of one randomly selected eye, centred on the region of the optic disc and the macula, with an autofocus camera. The photographic slides were assessed by trained graders, unaware of the participant's identity. The following lesions were graded: arteriovenous nicking, focal arteriolar narrowing, blot haemorrhages, flameshaped
Statistical analysis
All statistical procedures used SAS software (version 8.0). Follow-up time was defined as the number of days from the third examination visit to the date of hospital admission for the first stroke, death, last contact, or Dec 31, 1997, whichever occurred first.
We calculated Kaplan-Meier cumulative survival comparing presence versus absence of a focal retinal lesion, or between quintiles of AVR, and presented the result as 100x(1-Kaplan-Meier estimators). Relative risks for stroke were derived
Results
Comparisons of baseline characteristics between participants included (n=10 358) and excluded (n=5434) from the study are given in table 1. In general, those included were younger and had more years of education, the proportion who were white was higher, the proportions with hypertension, diabetes, and coronary artery disease were lower, and the mean values of blood pressure, body-mass index, and total cholesterol, triglyceride, and glucose concentrations were lower.
Among the participants
Discussion
Stroke affects an estimated 600 000 people per year in the USA and is the leading cause of severe neurological disability.21 Despite extensive research, the contribution of microvascular disease to the pathogenesis and evolution of stroke is not clear.23, 24 The retinal arterioles offer a unique opportunity to investigate the role of the microcirculation in cerebrovascular diseases, because they are accessible to direct non-invasive assessment, and they share anatomical and physiological
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