Adults with type 1 diabetes and mild cognitive impairment are twice as likely to develop dementia as those who have mild cognitive impairment without diabetes, according to findings from a study from Spain.
“The impairment of insulin signaling, the presence of low-grade inflammation and the pathways directly related to chronic hyperglycemia, such as the accumulation of advanced glycation end-products (AGEs) and the increase of oxidative stress play an essential role in the pathogenesis of [Alzheimer’s disease],” Rafael Simo, MD, of the Vall d’Hebron Research Institute at the Autonomous University of Barcelona, and colleagues wrote. “Since these pathways are significantly activated in [type 2 diabetes patients], it is reasonable to propose diabetes as an accelerator of [Alzheimer’s disease] in predisposed patients.”
In a retrospective, nested case-control study, Simo and colleagues analyzed data from 101 patients with type 2 diabetes and mild cognitive impairment (Clinical Dementia Rating scale of at least 0.5) and 101 controls with mild cognitive impairment but no diabetes; groups were matched by age. All patients were aged at least 60 years and attending a memory clinic for 2 years; mean follow-up was 28 months. Patients completed the Mini-Mental State Examination, the Hachinski Ischemia Scale, Clinical Dementia Rating and a neuropsychological exam, and they provided blood samples for apolipoprotein E (APOE) genotyping. Patients who developed dementia during follow-up were considered mild cognitive impairment converters.
Researchers observed that patients with type 2 diabetes had higher rates of conversion to dementia compared with those without diabetes (57.4% vs. 42.6%; P = .02), as well as a lower elapsed time for conversion (mean, 22.3 months vs. 26.2 months; P = .041). Most patients converted to Alzheimer’s disease (23%), followed by vascular dementia (14%), mixed dementia (11%), frontotemporal dementia (4%) and Lewy body dementia (1%). There were no between-group differences for dementia types.
After adjustment for age, sex, hypertension, dyslipidemia, APOE allele and time of follow-up, researchers found that type 2 diabetes was an independent risk factor for conversion to dementia (OR = 2.09; 95% CI, 1.32-4.96).
Researchers also noted that patients with type 2 diabetes who developed dementia had a higher prevalence of diabetic retinopathy than those who did not develop dementia (P = .016), whereas 8.6% of those who developed dementia presented with a history of severe hypoglycemia requiring hospitalization vs. one patient with severe hypoglycemia in the group that did not convert to dementia.
“We provide evidence that [type 2 diabetes] is an accelerator of dementia in patients with [mild cognitive impairment],” the researchers wrote. “The American Diabetes Association recommends individualizing diabetes treatment by taking into account the cognitive capacity of patients. Therefore, the identification of those patients most likely to develop dementia will be crucial for a personalized diabetes care.” – by Regina Schaffer
Disclosure: The Spanish Society of Diabetes supported this study. The researchers report no relevant financial disclosures.