Explanations for the lower rates of diabetic neuropathy in Indian Asians versus Europeans

Abstract

Objective: Risks of diabetes and cardiovascular disease are elevated worldwide in Indian Asians. However, risks of other diabetes-related complications, i.e., foot ulceration and amputation, also with a vascular basis, are substantially lower in Asians than in white Europeans in the U.K., possibly due to less neuropathy. We therefore compared signs, symptoms, and objective quantitative measures of diabetic neuropathy and their risk factors in Indian Asians and Europeans.

Research design and methods: This was a cross-sectional study of a population-based sample of age- and sex-matched adults with type 2 diabetes of European (95 male and 85 female) and Asian (96 male and 84 female) descent in the U.K. Patients were assessed for neuropathic symptoms, signs, nerve conduction, autonomic function, and quantitative sensory testing. Peripheral vascular function and other potential risk factors for neuropathy were measured. RESULTS Mean nerve conduction velocity Z scores were better in Asians (mean +/- SD 0.07 +/- 0.62) than in Europeans (-0.11 +/- 0.60; P = 0.007) and were explained by the shorter height, fewer pack-years smoked, and higher transcutaneous oxygen levels (TCpO(2)) in Indian Asians (P value for ethnic comparison attenuated to 0.2). Small fiber neuropathy was less prevalent in Indian Asians compared with Europeans (odds ratio 0.58 [95% CI 0.37-0.93]; P = 0.02) and was primarily accounted for by better TCpO(2) (0.70 [0.40-1.21]; P = 0.2).

Conclusions: Asians with diabetes have substantially less large and small fiber neuropathy than Europeans, despite comparable traditional risk factors. Independent from smoking, the lower risk of neuropathy in Asians is due to better skin microvascularization and may help explain the substantially reduced Asian foot ulcer risk.

Figure 1

Indexes of neuropathy by ethnicity: Indian Asians and Europeans. A: Neuropathy prevalence (percent). B: Nerve conduction studies (Z scores) (mean ± SE). C: Autonomic nerve function (mean ± SD). *Significantly different between the two groups, P < 0.05. **Significantly different between the two groups, P < 0.01. SBP, systolic blood pressure.