A diagnosis of diabetes in later life is associated with an increased risk of dementia, particularly in individuals with preexisting vascular disease.
A population-based matched cohort study in 225,045 seniors newly diagnosed with diabetes and 668,070 without found a 16% higher risk of dementia among those with diabetes.
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The association remained after adjustment for hypertension, coronary artery disease, cardiovascular disease, peripheral vascular disease and chronic kidney disease.
There is a growing body of evidence pointing to a link between diabetes and dementia, with their shared cardiometabolic risk factors suggesting dementia may be yet another vascular complication of diabetes, wrote Dr. Nisha Nigil Haroon of the University of Toronto.
“We hypothesized that exposure to even short-term hyperglycemia in late life can trigger or accelerate cognitive decline and therefore that incident diabetes is a risk factor for dementia after accounting for differences in cardiovascular disease and other common risk factors,” wrote Dr. Haroon and her colleagues.
The risk of dementia was slightly higher in men with diabetes (hazard ratio, 1.20; 95% confidence interval, 1.17-1.22) than in women (HR 1.14; 95% CI, 1.12–1.16) compared with healthy controls, according to a paper published online July 27 in Diabetes Care.
Previous cardiovascular disease doubled the risk of dementia in patients with diabetes, while hospitalization or emergency department visits for hypoglycaemia were associated with a 73% increase in dementia risk. Patients with chronic kidney disease or prior vascular disease were at increased dementia risk (Diabetes Care 2015, July 27 [doi: 10.2337/dc15-0491]).
There was a 1% increase in the risk of dementia per year following the diagnosis of diabetes, such that patients who had had diabetes for 10 years had a nearly 30% higher incidence of dementia. The median age of the cohort was 73 years.
“This is of serious concern given the aging population, increasing prevalence of diabetes, and the limited effective treatment currently available for dementia,” the authors wrote.
They also found that many commonly used vascular and antidiabetic medications did not impact the risk of dementia, except statins and calcium-channel blockers.
“Although such treatments have been postulated to be protective against dementia, numerous trials have failed to identify any beneficial role of glucose-, blood pressure–, or lipid-lowering agents on cognitive decline, as suggested by previous observational data,” they noted.
Insulin use was associated with a 74% greater risk of developing dementia.
Recent immigrants or South Asian or Chinese ethnicity had a reduced risk of dementia, and hypertension also seemed to lower the risk by 5%.
The authors found that individuals with diabetes living in the lowest income areas were 17% more likely to develop dementia than were those in the wealthiest area.
“Impaired health literacy, poorer self-management, and adverse health behaviors, such as smoking, have been linked to low income and could explain this association,” reported Dr. Haroon and her coauthors.
The Canadian Institutes of Health Research, the Heart and Stroke Foundation of Ontario, the Canadian Institutes of Health Research, the University of Toronto, and the Ontario Ministry of Health and Long-Term Care supported the study. One author reported an unrestricted grant from Amgen, but there were no other conflicts of interest declared.