Conclusions
The study of the epidemiology of diabetic neuropathy remains clouded by lack of agreement over diagnostic criteria and variation in subject selection methods. It is essential that agreement is reached over diagnosis, although it is hard at the present time to see how this is going to come about. One issue that may be relevant in this context is the basis on which the diagnosis should be made. Is diabetic neuropathy a condition which predisposes to clinical endpoints such as foot ulceration and amputation, in which case quantitative sensory testing should suffice, or is it a condition in which neurological function differs from that in a healthy population, in which case diagnosis may require a more detailed assessment?
The available data indicate that DSP is present in approximately 30% of hospital clinic patients, 20% of patients in primary care, and 10% of the total diabetic population, including both diagnosed and undiagnosed diabetes. The major confirmed risk factors are poor glycemic control, diabetes duration and height, with possible roles for hypertension (probably only in type 1 diabetes), age, smoking, hypoinsulinemia, and dyslipidemia.
There are as yet relatively few epidemiological data on the various manifestations of autonomic neuropathy from representative cohorts of diabetic patients, except for erectile dysfunction. Estimates from the available studies suggest that CAN is encountered one of every 4-6 men and ED is observed in one of every 2-3 men. Symptomatic orthostatic hypotension is relatively uncommon. Gastrointestinal symptoms are common in both diabetic and nondiabetic subjects, suggesting that a considerable proportion of these symptoms in diabetic patients is due to causes other than autonomic neuropathy
Clinic-based data suggest that particularly CAN but possibly also DSP are associated with increased mortality in diabetic patients, but prospective population-based studies are required to confirm these findings.
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