Salivary amyloid β42 levels in mild cognitive impairment among aged diabetics.

Purpose: The underlying pathology for cognitive decline in diabetic patients is uncertain. It was originally linked to vascular causes; however, possible contribution of Alzheimer's pathology was debated. This study explored the link between salivary amyloid β42 level (as a surrogate marker for Alzheimer's pathology) and mild cognitive impairment (MCI) among old diabetic patients.

Methods: A case-control study included 90 diabetic participants, ≥ 60 years of age, divided into 45 cases with MCI and 45 controls. Patients with history of head trauma, any central nervous system pathology, depression, dementia or delirium, those who received anticholinergic drugs, or refused to participate in the study were excluded. Assessment of the relationship between salivary Aβ42 level and neuropsychological performance was done using a battery consisting of the logical memory test, forward and backward digit span tests, category fluency test, go/no go test, stick design test, and second-order belief.

Results: Salivary Aβ42 levels were higher in MCI diabetics versus controls (P = 0.014), it predicted MCI among aged diabetics, even after adjustment for confounding vascular risk factors. Salivary Aβ42 had moderate accuracy to identify MCI (area under curve = 0.654, P = 0.008). At cut-off ≥ 47.5 pg/ml, sensitivity, specificity, positive predictive value and negative predictive value were 80%, 47%, 60% and 70%, respectively.

Conclusion: Current data support that MCI in diabetics, without CNS disorders, is associated with a surrogate marker of Alzheimer's pathology.