[Note: mild cognitive impairment is considered an intermediate stage between normal cognitive aging and dementias such as Alzheimer’s.]
Background: It remains unknown whether diabetes mellitus (DM) is a risk factor for mild cognitive impairment (MCI).
Objective: To investigate the association of DM with MCI using a population-based case-control design.
Design: Population-based case-control study.
Setting: Academic research.
Participants: Our study was conducted, among subjects aged 70 to 89 years on October 1, 2004, who were randomly selected from the Olmsted County (Minnesota) population.
Main Outcome Measure: We administered to all participants a neurologic examination, the Clinical Dementia Rating Scale, and a neuropsychological evaluation (including 9 tests in 4 cognitive domains) to diagnose normal cognition, MCI, or dementia. We assessed history of DM, DM treatment, and DM complications by interview, and we measured fasting blood glucose levels. History of DM was also confirmed using a medical records linkage system.
Results: We compared 329 subjects having MCI with 1,640 subjects free of MCI and dementia.
The frequency of DM was similar in subjects with MCI (20.1%) and in subjects without MCI (17.7%) (odds ratio [OR], 1.16; 95% confidence interval [CI], 0.85-1.57).
However, MCI was associated with:
- Onset of DM before age 65 years (OR, 2.20; 95% CI, 1.29-3.73), [an OR – “odds ratio” – of 1.0 would mean no association between onset of diabetes before age 65 and having mild cognitive impairment. In this case the statistics produced an odds ratio of 2.2, meaning MCI was more than twice as likely if diabetes developed before age 65.
- DM duration of 10 years or longer (OR, 1.76; 95% CI, 1.16-2.68),
- Treatment with insulin (OR, 2.01; 95% CI, 1.22-3.31),
- And the presence of DM complications (OR, 1.80; 95% CI, 1.13-2.89) after adjustment for age, sex, and education. Analyses using alternative definitions of DM yielded consistent findings.
Conclusion: These findings suggest an association of MCI with earlier onset, longer duration, and greater severity of DM.
Source: Archives of Neurology, August 2008;65(8):1066-1073. by Roberts RO, Geda YE, Knopman DS, Christianson TJ, Pantratz VS, Boeve BF, Vella A, Rocca WA, Petersen RC. Divisions of Epidemiology, Biostatistics, Health Sciences Research, Psychiatry and Psychology, Neurology, and Endocrinology, Department of Medicine, College of Medicine, Mayo Clinic, Rochester, Minnesota, USA.