Type 2 diabetes mellitus, cognitive impairment and dementia

AIMS: We set out to examine the evidence for an association between cognitive impairment or dementia and the presence of Type 2 diabetes mellitus (DM). We also sought evidence of potential mechanisms for such an association. METHODS: A literature search of three databases was performed and the reference lists of the papers so identified were examined, using English language papers only. RESULTS: We found evidence of cross-sectional and prospective associations between Type 2 DM and cognitive impairment, probably both for memory and executive function. There is also evidence for an elevated risk of both vascular dementia and Alzheimer's disease in Type 2 DM albeit with strong interaction of other factors such as hypertension, dyslipidaemia and apolipoprotein E phenotype. Both vascular and non-vascular factors are likely to play a role in dementia in diabetes. CONCLUSIONS: Current classification structures for dementia may not be adequate in diabetes, where mixed pathogenesis is likely. Further research into the mechanisms of cognitive impairment in Type 2 DM may allow us to challenge the concept of dementia, at least in these patients, as an irremediable disease.