THE PREVALENCE BY STAGED SEVERITY OF VARIOUS TYPES OF DIABETIC NEUROPATHY, RETINOPATHY, AND NEPHROPATHY IN A POPULATION-BASED COHORT - THE ROCHESTER DIABETIC NEUROPATHY STUDY

The magnitude of the health problem from diabetic neuropathies remains inadequately estimated due to the lack of prospective population-base d studies employing standardized and validated assessments of the type and stage of neuropathy as compared with background frequency. All Ro chester, Minnesota, residents with diabetes mellitus on January 1, 198 6, were invited to participate in a cross-sectional and longitudinal s tudy of diabetic neuropathies (and also of other microvascular and mac rovascular complications). Of 64,573 inhabitants on January 1, 1986 in Rochester, 870 (1.3%) had clinically recognized diabetes mellitus (Na tional Diabetes Data Group criteria), of whom 380 were enrolled in the Rochester Diabetic Neuropathy Study. Of these, 102 (26.8%) had insuli n-dependent diabetes mellitus (IDDM), and 278 (73.2%) had non-insulin- dependent diabetes mellitus (NIDDM). Approximately 10% of diabetic pat ients had neurologic deficits attributable to nondiabetic causes. Sixt y-six percent of IDDM patients had some form of neuropathy; the freque ncies of individual types were as follows: polyneuropathy, 54%; carpal tunnel syndrome, asymptomatic, 22%, and symptomatic, 11%; visceral au tonomic neuropathy, 7%; and other varieties, 3%. Among NIDDM patients, 59% had various neuropathies; the individual percentages were 45%, 29 %, 6%, 5%, and 3%. Symptomatic degrees of polyneuropathy occurred in o nly 15% of IDDM and 13% of NIDDM patients. The more severe stage of po lyneuropathy, to the point that patients were unable to walk on their heels and also had distal sensory and autonomic deficits (stage 2b) oc curred even less frequently-6% of IDDM and 1% of NIDDM patients. Overa ll, two thirds of diabetic patients have objective evidence for some v ariety of neuropathy, but only about 20% have symptoms, and only 6% of IDDM and only 1% of NIDDM patients have sufficiently severe polyneuro pathy to be graded stage 2b, and none were graded stage 3. Approximate ly one quarter of patients had subclinical carpal tunnel syndrome, but only 7.7% had symptomatic carpal tunnel syndrome. Thus, diabetic peri pheral neuropathy is frequent but less severe than generally thought. As generally believed, however, neuropathy, retinopathy, and nephropat hy are significantly associated.