Differential association of retinal arteriolar and venular caliber with diabetes and retinopathy

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Abstract

Aims

To describe the relationship of retinal arteriolar and venular caliber with diabetes, retinopathy and hyperglycemia, in an Asian Indian population.

Methods

This was a population-based cross-sectional study of 3400 (75.6% response rate) Singapore ethnic Indians aged 40–80 years. Central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were obtained using a validated computer-assisted program. Diabetes mellitus was identified using standardized criteria. Diabetic retinopathy was graded based on the modified Airlie House Classification System.

Results

There were 980 (32.2%) participants with diabetes. Of these, 327 (33.4%) had diabetic retinopathy. After multivariate adjustment, diabetic persons had a wider CRAE (145.23 μm vs 142.38 μm, P < 0.001). This relationship was stronger in persons without hyperlipidemia (P-interaction < 0.1). Among diabetic participants, wider CRVE was related to increasing severity of retinopathy (P for trend < 0.05) and this association may be altered by hypertensive status. Retinal arteriolar caliber widened with increasing glucose (P < 0.001) and HbA1C (P < 0.001) levels.

Conclusions

In Indian adults, wider retinal arteriolar caliber is associated with diabetes and hyperglycemia, while wider retinal venular caliber is associated with diabetic retinopathy. This is consistent with white populations and confirms the differential systemic association of retinal vascular caliber in Asian Indians.

Introduction

Diabetes mellitus (DM) is a major cause of morbidity and mortality in over 300 million people worldwide, with diabetic retinopathy being the commonest cause of preventable blindness in working aged adults, affecting 1 in 3 persons [1], [2], [3]. The magnitude of this problem is particularly striking in certain populations in Asia, with the number of Indians with diabetes expected to reach almost 80 million by year 2030 [4], and thus, every fifth person with diabetes will be an Indian. As compared to other Asian groups, such as Chinese and Malays, Indians develop diabetes at a younger age, have a higher lifetime risk of diabetes and are at a higher risk of complications despite treatment and follow-up adherence [5], [6], [7], [8].

The retinal vessels provide an opportunity to observe and study early microvascular changes in diabetes development. Recent studies show the caliber of the retinal vessels can be measured quantitatively from photographs, and variations in caliber are associated with diabetes, diabetic retinopathy and hyperglycemia, suggesting that retinal vascular caliber may be a surrogate marker of diabetes and its complications [9], [10], [11], [12], [13], [14], [15]. However, the relationship between retinal vascular caliber with diabetes and retinopathy has not been consistently reported in different racial/ethnic groups. Studies in white populations and a Singapore Malay population showed that wider retinal arterioles were associated with diabetes [11], [12], [13], [14]. However, in the Multi-Ethnic Study of Atherosclerosis (MESA) study, retinal arteriolar caliber was not associated with diabetes in non Whites and there were significant ethnic variations in the association between diabetes and retinal vascular calibers. In another multiethnic Asian population study, diabetes was associated with increasing retinal arteriolar calibers but this relationship was not statistically significant in individual ethnic groups [15]. Studies also suggested inconsistency in the relationship between retinal vascular caliber with microvascular complications such as diabetic retinopathy in different racial groups [11], [12], [13], [14].

Because Asian Indians have a higher prevalence of diabetes and risk of diabetic microvascular complications, it is informative to examine these relationships in this ethnic group. A previous study with a small number of ethnic Indians (n = 727) did not find statistically significant relationships between retinal vascular caliber and diabetes when stratified by ethnic groups [15]. To date, no studies have examined the relationship between retinal vascular caliber and diabetic retinopathy in ethnic Indians. The purpose of this study is therefore to determine the relationship of retinal vascular caliber with diabetes and to its primary microvascular complication, diabetic retinopathy in an Asian Indian population residing in Singapore.

Section snippets

Study population

The Singapore Indian Eye Study (SINDI) is a population-based cross-sectional survey of 3400 (75.6% response rate) ethnic Indians aged 40–80 years and living in Singapore. Data was collected from May 2007 through December 2009. Subjects were selected using an age-stratified (by 10-year age group) random sampling method, from a computer-generated list provided by the Singapore Ministry of Home Affairs. Detailed methodology has been described elsewhere [16], [17]. Written, informed consent was

Results

Of the 3400 participants, 3395 (99.9%) had fundal photographs. We excluded the subjects with ungradable retinal fundus photographs (n = 193) due to poor image quality or those without at least six large gradable arterioles or venules, and those with missing data on diabetic and diabetic retinopathy status (n = 119). We also excluded the subjects with proliferative diabetic retinopathy (n = 19) and subjects with previous laser treatment (n = 21), as this could have an effect on retinal vascular caliber

Discussion

In this large population-based study, we examined the variation of retinal vascular caliber in association with diabetes, retinopathy status and glycemia among Asian Indians residing in Singapore. To our knowledge, our study is the largest Indian population (3400 ethnic Indians) to examine correlates of retinal vascular caliber with diabetes and retinopathy and possible effect modification by cardiovascular risk factors. We showed that a wider retinal arteriolar caliber was related to diabetic

Funding

Biomedical Research Council (BMRC), 08/1/35/19/550.

Conflict of interest

The authors declare that they have no conflict of interest.

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