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Diabetic Polyneuropathy Not Related to Impaired Glycemia

Impaired glycemia (IG) is not a risk factor for typical or atypical diabetic polyneuropathy, according to the findings of a population-matched prospective study.

The authors note that the findings regarding associations between IG and both typical and atypical diabetic polyneuropathy have been inconsistent. “de Neeling et al. studied nerve conduction abnormality and other neurophysiologic tests in patients without and with [impaired glucose tolerance (IGT)], new-onset diabetes, and prevalent diabetes and found ‘large fiber nerve dysfunction’ within the range of IGT to diabetes (P < 0.05)," the authors write. "However in a study by Isak et al. using objective nerve conduction measurements, no increase attributable to IG was found."

The authors conducted a survey to identify patients without IG, with IG, and with new diabetes in local population-based medical and laboratory registries. Among the 542 age- and sex-matched volunteers (150 with non-IG, 174 with IG, and 218 with new diabetes) who completed the study, the incidence of diabetic neuropathy was not significantly different between individuals with IG and those without IG for both narrowly (odds ratio [OR], 0.9; 95% confidence interval [CI], 0.2 – 4.3; P = .85) and broadly (OR, 1.0; 95% CI, 0.5 – 1.9; P = 1.00) defined diabetic neuropathy.

However, the frequency of diabetic neuropathy was higher among individuals with new diabetes, particularly when diabetic neuropathy was defined narrowly (new diabetes vs non-IG: OR, 4.1; 95% CI, 1.2 – 14.4; P = .02; new diabetes vs IG: OR, 4.8; 95% CI, 1.4 – 16.7; P < .01).

In the restudy, the authors defined non-IG, IG, and new diabetes as follows: non-IG: fasting plasma glucose (FPG) level lower than 5.6 mmol/L, a 2-hour oral glucose tolerance test (OGTT) level lower than 7.8 mmol/L, and the absence of new diabetes; IG: FPG level of 5.6 mmol/L or higher and lower than 7.0 mmol/L, a 2-hour OGTT level of 7.8 mmol/L or higher and lower than 11.1 mmol/L; new diabetes: FPG level of 7.0 mmol/L or higher, 2-hour OGTT level of 11.1 mmol/L or lower, or hemoglobin A1c levels of 6.5% or higher.

The incidence of retinopathy and nephropathy was higher in the group with new diabetes (9.4% and 10.7%, respectively), which was higher than that in the non-IG (3.4% and 4.1%, P = .03 and P = .02, respectively) and IG (4.7% and 4.7%, P = .08 and P = .03, respectively) groups. No differences in the incidence of retinopathy and nephropathy were observed between the IG and non-IG groups.

The authors mention that their findings might have several implications. “By showing that IG alone does not cause diabetic micro-vessel complications, our results support present criteria for the diagnosis of diabetes, based on the idea that the lowest level of chronic hyperglycemia that induces microvessel complications should be the minimal criteria for the diagnosis of diabetes,” the authors write.

“Our findings, however, should not allay concerns about IG as a risk covariate for macro- and microvessel complications since IG usually leads to type 2 diabetes, which is known to cause such complications.”

Diabetes Care. 2012;35:584-591