Peripheral neuropathy is a devastating complication of diabetes mellitus because of the debilitating symptoms it causes or associated higher risk of other complications, in particular those involving the lower extremity. This chapter will review the prevalence, incidence, and risk factors for different types of diabetic neuropathy. There are seven major types of diabetic neuropathy: (1) distal symmetric polyneuropathy, (2) autonomic neuropathy, (3) nerve entrapment syndromes, (4) proximal asymmetric mononeuropathy (also known as diabetic amyotrophy), (5) truncal radiculopathy, (6) cranial mononeuropathy, and (7) chronic inflammatory demyelinating polyradiculopathy (CIDP). This chapter will focus mainly on the first two types of neuropathy, but will review the available data on the epidemiology of the other types of neuropathy. Cross-sectional or case-control studies conducted in a population-based sample (such as a defined community or health plan enrollment) were considered for this chapter based on review of Medline citations using the keywords "epidemiology," "diabetes," and "neuropathy" from 1966 to February 2005 review of bibliographies of the articles obtained from the Medline search for relevant citations, and review of the authors' files. Clinic-based cross-sectional or case-control studies have not been considered except in the case of rare conditions, for which no other data exists. All prospective studies, and some randomized controlled trials, were considered. Of the five community-based cross-sectional studies reviewed of subjects with type 2 diabetes that presented data on risk factors for neuropathy, three reported a higher prevalence of this outcome with longer diabetes duration and higher glycosylated hemoglobin, and two found neuropathy prevalence correlated with age and height. Only three community-based cross-sectional studies addressed neuropathy prevalence in subjects with type 1 diabetes in association with risk factors. Two of these investigations reported a correlation between diabetes duration and neuropathy prevalence. No other significant risk factor was reported by more than one community-based study done with subjects with type 1 diabetes. Prospective research on the risk of distal symmetric polyneuropathy confirms its relationship to poorer glycemic control as reflected by fasting plasma glucose or hemoglobin A1c (HbAlc) at baseline. Four prospective studies reported duration of diabetes as a risk factor for neuropathy, three reported smoking as a risk factor, two reported age and two reported baseline coronary artery disease as risk factors for neuropathy. The literature on risk factors for diabetic autonomic neuropathy can be characterized as smaller in size and less consistent in comparison with that available for distal symmetric polyneuropathy. The only risk factor reported in more than one study was female gender, found to be associated with higher risk by two authors. There have been no prospective population-based studies
From: Contemporary Diabetes: Diabetic Neuropathy: Clinical Management, Second Edition Edited by: A. Veves and R. Malik © Humana Press Inc., Totowa, NJ
of diabetic amyotrophy and mononeuropathies in subjects with diabetes. However, some prevalence figures for these types of neuropathy can be derived from a few cross-sectional studies, which are described in the chapter. CIDP is a relatively new diagnosis. In 1991, the American Academy of Neurology defined diagnostic clinical and electrophysiological criteria for CIDP. All studies on CIDP are cross-sectional and clinic-based.
Key Words: Diabetic neuropathy; diabetes; epidemiology; incidence; prevalence; risk factors. INTRODUCTION
Peripheral neuropathy is a devastating complication of diabetes mellitus (DM) because of the debilitating symptoms it causes or associated higher risk of other complications, in particular those involving the lower extremity. The epidemiology of diabetic neuropathy is not as well understood in comparison with other complications of this metabolic disorder, including retinal, renal, and coronary artery disease. Different peripheral nerves may be damaged through a variety of pathological processes as described in other chapters of this book. This chapter will review the prevalence, incidence, and risk factors for different types of diabetic neuropathy. The natural history of diabetic neuropathy will be briefly described regarding foot complications.
There are seven major types of diabetic neuropathy:
1. Distal symmetric polyneuropathy.
2. Autonomic neuropathy.
3. Nerve entrapment syndromes.
4. Proximal asymmetric mononeuropathy (also known as diabetic amyotrophy).
5. Truncal radiculopathy.
6. Cranial mononeuropathy.
7. Chronic inflammatory demyelinating polyradiculopathy (CIDP).
This chapter will focus mainly on the first two types of neuropathy, but will review the available data on the epidemiology of the other types of neuropathy. With the exception of nerve entrapment syndromes these remaining types occur infrequently.
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