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.