Background: Diabetes mellitus is associated with cognitive dysfunction, but it is not clear whether the disorder increases the risk of conversion from mild cognitive impairment to dementia.
Aims: To determine the association between diabetes mellitus and dementia conversion in people with mild cognitive impairment (Peterson's criteria) in a prospective community-based study.
Method: People over 65 years old were approached through primary care practices in south London, UK, and those with mild cognitive impairment (n = 103) were followed up for 4 years. Presence of diabetes was established from self-report and information from general practitioners.
Results: Nineteen participants progressed to dementia, with the predominant diagnosis being probable or possible Alzheimer's disease (in 84%). Only diabetes mellitus was associated with progression to dementia (hazard ratio 2.9, 95% CI 1.1-7.3) after adjustment for sociodemographic factors, APOE4, premorbid IQ and other health conditions.
Conclusions: Diabetes mellitus increases not only the risks of dementia and mild cognitive impairment but also the risk of progression from such impairment to dementia.