Is cognitive impairment associated with the presence and severity of peripheral neuropathy in patients with type 2 diabetes mellitus?

BACKGROUND: Peripheral Diabetic Neuropathy (PDN) and cognitive impairment are complications of Diabetes Mellitus (DM) that seem to share several underlying mechanisms. The aim of this study was to investigate whether diabetic patients would have worse cognitive function than non diabetic individuals and within diabetic patients, whether those with PDN would present an even more significant cognitive impairment. FINDINGS: Ninety four (94) outpatients with Type 2 DM were sequentially evaluated. Also, Fifty four (54) healthy individuals were sequentially selected to match the diabetic group. For the assessment of neuropathy, Portuguese versions of the Neuropathy Disability Score (NDS) and Neuropathy Symptom Score (NSS) were used. Global cognitive function was assessed by using the Portuguese Version of the Mini-Mental State Examination (MMSE), Trail Making Tests A and B and Verbal Fluency Test. Significantly lower scores were found in the Type 2 DM group in comparison to control group in the MMSE (25.7 [16–30] vs 27.6 [19–30]; p <0.001). Within T2DM group, forty five (45) patients were diagnosed with PDN. No differences were found between patients with and without PDN in all cognitive tests (p >0.05 in all comparison). No correlation was also found among NSS, NDS and any of the cognitive tests. CONCLUSION: Although diabetic patients do have a worse cognitive function, this impairment does not seem to be related to the presence and/or severity of PDN.