Accelerated Progression From Mild Cognitive Impairment to Dementia in People With Diabetes

OBJECTIVE The effect of diabetes on mild cognitive impairment (MCI) and its conversion to dementia remains controversial. We sought to examine whether diabetes and pre-diabetes are associated with MCI and accelerate the progression from MCI to dementia. RESEARCH DESIGN AND METHODS In the Kungsholmen Project, 963 cognitively intact participants and 302 subjects with MCI (120 with amnestic MCI [aMCI] and 182 with other cognitive impairment no dementia [oCIND]) age ≥ 75 years were identified at baseline. The two cohorts were followed for 9 years to detect the incident MCI and dementia following international criteria. Diabetes was ascertained based on a medical examination, hypoglycemic medication use, and random blood glucose level ≥ 11.0 mmol/l. Pre-diabetes was defined as random blood glucose level of 7.8-11.0 mmol/l in diabetes-free participants. Data were analyzed using standard and time-dependent Cox proportional-hazards models. RESULTS During the follow-up period, in the cognitively intact cohort, 182 people developed MCI (42 aMCI and 140 oCIND), and 212 developed dementia. In the MCI cohort, 155 subjects progressed to dementia, the multi-adjusted hazard ratio (95% CI) of dementia was 2.87 (1.30-6.34) for diabetes, and 4.96 (2.27-10.84) for pre-diabetes. In a Kaplan-Meier survival analysis, diabetes and pre-diabetes accelerated the progression from MCI to dementia by 3.18 years. Diabetes and pre-diabetes were neither cross-sectionally nor longitudinally associated with MCI. CONCLUSIONS Diabetes and pre-diabetes substantially accelerate the progression from MCI to dementia, and anticipate dementia occurrence by more than 3 years in people with MCI. The association of diabetes with the development of MCI is less evident in old people.