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Diabetes and dementia risk – the evidence
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Diabetes and dementia risk – the evidence

Diabetes, especially type 2, and pre-diabetes syndromes appear to be risk factors for dementia. A recent review concluded that type 2 diabetes is associated with increased risk of Alzheimer’s disease and vascular dementia [1]. Another review reported meta-analyses that found diabetes was associated with a 47% increased risk of any dementia, a 39% increased risk of Alzheimer’s disease, and a 138% increased risk of vascular dementia [2].

Diabetes has also been associated with greater risk for cognitive decline in several studies following people for 2 – 7 years [2]. Global cognitive function and executive function have been shown to be affected by diabetes.

Few studies have examined the effect of treatment of diabetes on dementia risk and the results are mixed [2]. The effect of the duration of diabetes on dementia risk has also not been determined, however duration has been associated with increased risk of cognitive decline [2].

Insulin resistance has also been associated with increased dementia risk. Insulin inhibits the degradation of beta amyloid through competitive inhibition of insulin-degrading enzyme, thus increasing the formation of plaques. Hyperinsulinemia may also activate inflammation in the brain, thereby increasing the risk of dementia [2].

The mechanisms underpinning the association between diabetes and dementia risk are unclear. Multiple processes may be involved, such as the effects of insulin resistance, vascular pathology, oxidative stress, glucocorticoids excess and inflammation [1,2].

References

  • Strachan MWJ, et al. The relationship between type 2 diabetes and dementia. British Medical Bulletin, 2008, 88:131-146.
  • Lu F-P, et al. Diabetes and the risk of multi-system aging phenotypes: a systematic review and meta-analysis. PLoS ONE, 2009, 4(1): e4144. doi:10.1371/journal.pone.0004144.