Diabetes mellitus has been associated to cognitive capacity deficits of different nature. The association of different diabetes and types of dementia has been speculated on, in particular the Alzheimer and vascular types. In the case of diabetes type 1, that is to say, the insulin dependent form there is a decrease in the mental flexibility and a relatively slower mental agility is appraised. In the case of the diabetes type 2, the most frequent form, typical of adults and very related to life habits, changes have been registered referring to learning capacity, memory, flexibility and mental agility.

There are investigations in which an increase in the speed of declivity of the cognitive capacities, have been found in aged diabetics patients. The real mechanisms -of this process- are yet not known. For some scientists it is a poorly controlled arterial hypertension, whereas for others the blame is on a badly controlled glycemia. Nevertheless, the relation with dementia is not so clear. Although a study determined that 80% of the patients affected by Alzheimer had some alteration of the glucose metabolism, another study -made in patients with dementia- found that diabetes was very infrequent in the lunatic sub-group of Alzheimer type.

To clear these doubts, as far as it could be possible, a group of Dutch and British investigators made a search of all studies conducted from 1966 until August of 2005. They found a grand total of 3.021 studies, of which they selected a good sample, being 43 of them rated as relevant.

The data demonstrated an evident association between diabetes mellitus and the risk of developing dementia. The conclusion of this study urges towards the implementation of further studies.