Six year incidence and progression of diabetic retinopathy: Results from the Mauritius diabetes complication study

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Abstract

Aims

To determine the incidence, progression and risk factors for diabetic retinopathy in the multiethnic population of Mauritius.

Method

A longitudinal, population-based study was conducted in Mauritius, during 1987, 1992 and 1998. Participants identified through the study as having diabetes (both known and newly diagnosed, by self-report and oral glucose tolerance test) and one in four participants with impaired glucose tolerance (IGT) underwent complications screening in 1992 and 1998. Retinal photographs were taken using a TRC-50VT retinal camera in three fields of the right eye (centred on the optic disc; macula (temporal to the optic disc); and nasal to disc). Photographs were graded according to a simplified version of the Wisconsin grading system.

Results

The 6-year incidence of diabetic retinopathy was 23.8% (sight-threatening in 0.4%). Among those with known diabetes mellitus (KDM) and free of retinopathy at baseline the incidence of non-proliferative diabetic retinopathy (NPDR) was 29.2% and proliferative diabetic retinopathy (PDR) was 1.0%. Among those with newly diagnosed diabetes mellitus (NDM) at baseline the incidence of NPDR was 19.1% (no incident cases of PDR were found). Independent risk factors for retinopathy using the baseline population characteristics were duration of diabetes and fasting plasma glucose.

Conclusions

This is one of the few recent population-based studies of diabetic retinopathy undertaken in a developing nation. The incidence of retinopathy in Mauritius was high among those with NDM at baseline, with one in five developing retinopathy over 6 years. These results support the concept that screening for diabetes is important.

Section snippets

Patients and methods

The population, methods and response rates of the study have been described in detail elsewhere [15], [16]. In brief, for the baseline survey in 1987, a population-based sample of people aged ≥25 years was drawn from 10 randomly selected areas of Mauritius. In 1992 and 1998, all participants were invited for follow-up, as were all other eligible residents in the 10 areas, and in another three purposefully selected areas. The response rates for the surveys were 86% in 1987, 88% in 1992 and 87%

Results

Among those with diabetes (KDM and NDM) and free of retinopathy at baseline, the 6 year incidence of retinopathy (NPDR and PDR) was 23.8% (proliferative in 0.4%; Table 2). In those with KDM at baseline the incidence of NPDR was 29.2% and PDR was 1.0%. In those with NDM at baseline the incidence of NPDR was 19.1% (no incident cases of PDR were found). The incidence of retinopathy increased with longer duration of diabetes; baseline duration <4 years 19.2%, 4–8 years 29.2%, >8 years 66.7%. Among

Conclusions

A limited number of longitudinal population-based studies of diabetic retinopathy have been conducted in developing countries and few studies in general have included those with newly diagnosed diabetes and impaired glucose tolerance. The 6-year incidence of retinopathy in Mauritius was 30.2% among those with KDM at baseline and 19.1% among those with NDM at baseline. The incidence of retinopathy was similar to that found in populations from developed countries [19], [20], [21]. In the

Acknowledgements

This study undertaken with the support and collaboration of the Ministry of Health (Mauritius), the World Health Organisation (Geneva, Switzerland), International Diabetes Institute (Melbourne, Australia), the University of Newcastle upon Tyne (UK), and the National Public Health Institute (Helsinki, Finland). This study was partially funded by US National Institutes of Health Grant DK-25446. R. Tapp is supported by a grant from the National Health and Medical Research Council of Australia

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