Cognitive decline associated with dementia and type 2 diabetes: the interplay of risk factors

Excerpt

The possible association between type 2 diabetes and dementia, Alzheimer’s disease in particular, has been shrouded in confusion for some time, with some researchers noting that Alzheimer’s patients are rarely diabetic [1] but others suggesting diabetes to be a major risk factor for the disease [2]. Since an earlier review of the evidence [3], a number of things have become clearer. First, histopathological examinations of the brains of type 1 and type 2 diabetic patients have demonstrated that diabetes as such does not produce the amyloid plaques and neurofibrillary tangles considered hallmarks of Alzheimer’s disease [4]—a finding supported by a recent extensive post-mortem examination [5]. Second, research has shown that, in non-demented patients with type 2 diabetes, cognitive deficits are relatively mild before the age of 70 years, although they increase in frequency and severity thereafter [6]. Finally, people with type 2 diabetes who maintain less than optimal glycaemic control (i.e. with many occurrences of high blood glucose levels) are more likely to start manifesting cognitive deficits. Interestingly, improving glycaemic control in this population can reduce these cognitive deficits [7], suggesting that cognitive deficits might not be permanent in patients in whom presentation is early. …