Diabetic neuropathy in Mauritius: prevalence and risk factors

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Abstract

The study of diabetic neuropathy has been primarily in Europids, despite the high prevalence of diabetes in other populations. We set out to ascertain the prevalence of diabetic neuropathy and its risk factors in the island nation of Mauritius. Population surveys were carried out in 1987 and 1992 in Mauritius to establish the prevalence of Type 2 diabetes. In the second survey, vibration perception threshold (VPT) was also measured at the great toe in 847 subjects with diabetes, 204 subjects with impaired glucose tolerance and 127 subjects with normal glucose tolerance. Neuropathy was defined as levels of VPT exceeding the mean plus 2 standard deviations defined separately for three age groups of Mauritian non-diabetic subjects. Risk factors for neuropathy were identified cross sectionally from the 1992 data, and longitudinally from the 1987 data. Neuropathy was detected in 8.3% of the 847 diabetic subjects (12.7% of those with known diabetes, and 3.6% of those with newly diagnosed diabetes). Logistic regression identified diabetes duration (odds ratio [95% CI]; 1.08 [1.04–1.13] per year, P=0.0002), treatment with insulin or oral hypoglycaemic agents (2.63 [1.36–5.09], P=0.004) and greater height (1.36 [1.19–1.57] per 5 cm, P<0.001) as risk factors for neuropathy, in the cross sectional analysis. In the longitudinal analysis, diabetes duration (1.11 [1.05–1.18] per year, P=0.001), fasting glucose (1.12 [1.03–1.22] per mmol/l, P=0.01) and height (1.23 [1.03–1.45] per 5 cm, P=0.02) were associated with neuropathy. A lower 2-h plasma insulin was also associated with neuropathy in the longitudinal analysis. The prevalence of diabetic neuropathy in Mauritius is the lowest reported for any population, but the risk factors associated with it are similar to those previously found.

Introduction

Peripheral neuropathy is a common and important complication of long term diabetes mellitus. It results in pain, and more importantly is a major contributor to foot ulceration and lower limb amputation. A number of studies have determined both the prevalence of peripheral neuropathy and associated risk factors. Most studies of diabetic neuropathy have been on Europid subjects, and despite different methodological and diagnostic approaches, several reports have found very similar prevalence rates, at around 30% 1, 2, 3, 4. In older populations, the rate has been reported to be as high as 50% [5]. Studies in non-Europid populations are limited, but two studies of Native Americans indicate a rate of 19% 6, 7. Several factors have been identified as being associated with neuropathy in both cross sectional and prospective studies. Glycaemic control, diabetes duration and age, together with the presence of other diabetic complications are frequently reported as being associated with neuropathy. Recently, hypertension in Type 1 diabetes [8], and hypoinsulinaemia in Type 2 diabetes [9]have been strongly associated with peripheral neuropathy in prospective studies. In a population based survey of the Indian Ocean island of Mauritius in 1987, diabetes (almost universally Type 2) was found in 11.9% of adults aged 25–74 years [10]. In a follow-up study in 1992, we measured vibration perception threshold (VPT) [11], with the aim of determining the prevalence of neuropathy, and its associated risk factors, both cross sectionally, and also longitudinally for those subjects who took part in both the 1987 and 1992 surveys.

Section snippets

Subject selection

Mauritius is an island nation approximately 800 km east of Madagascar. The population consists of 70% Asian Indians, 2.1% Chinese and 27.9% `general population' who are predominantly people of African ancestry (Creoles) with varying amounts of European, Malagasy and Indian admixture.

In the 1987 survey, all enumerated adults (both diabetic and non-diabetic) aged 25–74 years living in ten randomly selected population centres, plus a purposely selected area of Chinatown in the capital Port Louis

Results

Demographic details of the 1178 subjects who had VPT measurements are shown in Table 1. There were 554 subjects who were classified as having diabetes in 1987, and were still alive in 1992. There was an 88% response rate to the 1992 survey, and 78% of all diabetic subjects at the 1992 survey attended for VPT measurement. Thus, 374 diabetic subjects were available for the longitudinal analysis. There were no significant differences in age, sex, diabetes status (known or new) or diabetes duration

Discussion

There is no single standardised method of diagnosing diabetic neuropathy, but quantitative sensory tests (such as VPT) are particularly suited to large field studies, and have been used to accurately classify neuropathy in a number of previous studies 5, 7, 17, 22. Furthermore, the only two prospective studies that strongly link neuropathy to foot ulceration and amputation used only a single quantitative sensory test 7, 17. Therefore, we used VPT, and derived normal values from the local

Acknowledgements

This study was undertaken with the support and collaboration of the Ministry of Health (Mauritius) and the World Health Organization (Geneva and Mauritius). The study was partially supported by National Institutes of Health Grant DK-25446. Jonathan Shaw is supported by a grant from the Institute for Diabetes Discovery, Connecticut, USA.

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