Type 1 diabetes-associated cognitive impairment and diabetic peripheral neuropathy in Chinese adults: results from a prospective cross-sectional study

Background: To compare neurocognitive functioning of Type 1 diabetic mellitus (T1DM) and healthy adults, and explore risk factors of cognitive dysfunction of T1DM patients, especially the association between cognitive impairment and diabetic peripheral neuropathy (DPN). Methods: Seventy T1DM (age: 32.17 +/- 9.57yr., duration: 8.99 +/- 7.02yr) patients and 48 healthy volunteers were included. All subjects received evaluation of MMSE and MoCA scales. Cognitive function of T1DM patients was evaluated in different cognitive domains. Risk factors affecting cognitive function were further explored. Results: Three patients with educational level <= 6-year were excluded from final analysis. Scores of both MMSE (28.4 +/- 1.7 vs. 29.1 +/- 1.0, P=0.005) and MoCA scales (25.9 +/- 2.7 vs.27.1 +/- 2.4, P=0.017) in T1DM group were lower than that in control group. For MMSE scale, scores of orientation (9.60 +/- 0.79 vs.9.87 +/- 0.39, P<0.001) and language function (8.56 +/- 0.65 vs.8.83 +/- 0.38, P<0.001) in T1DM groups were lower than that in control group. For MoCA scale, scores of attention and concentration (2.30 +/- 0.74 vs.2.57 +/- 0.58, P<0.001), visuospatial/executive function (4.32 +/- 0.91 vs.4.64 +/- 0.63, P<0.001), memory (2.96 +/- 1.50 vs.3.66 +/- 1.28, P<0.001), language function (5.71 +/- 0.69 vs.5.87 +/- 0.39, P=0.007), and abstraction (1.55 +/- 0.68 vs.1.82 +/- 0.42, P<0.001) were lower in T1DM group than that in control group. Logistic regression showed age, fasting C peptide, educational level and nerve conduction velocity (NCV) were associated with cognitive dysfunction diagnosed by MoCA scores for the patients with type 1 diabetes. Conclusions: T1DM adults had mild to moderate cognitive impairment, mainly presenting as dysfunctions of attention and concentration, visuospatial/executive, language, and abstraction. In addition to age, fasting C peptide level, and educational level, DPN, as a diabetic complication, was identified to be associated with cognitive impairments.