medwireNews: Research published in JAMA suggests the risk for dementia increases with younger age at type 2 diabetes diagnosis, with the risk further increased in people who have a stroke.
“Taken together, these findings highlight the importance of age at onset of diabetes and cardiovascular comorbidity in persons with diabetes for risk of dementia,” write Archana Singh-Manoux (Université de Paris, France) and study co-authors.
Their conclusions are based on data from 10,095 participants from the UK’s Whitehall II prospective study. Between 1985 and 2019, 16.9% of these people developed diabetes, and 6.3% were diagnosed with dementia.
Overall, people with diabetes were more likely than those without to develop dementia, at rates of 6.25 versus 1.76 per 1000 person–years when treating diabetes as a time-varying measure.
But age at diabetes onset modified the dementia risk. For example, among people aged 70 years, each 5-year younger age of diabetes onset was associated with a significant 24% increase in the risk for dementia, relative to remaining free of diabetes.
At this age, the rate of dementia in people without diabetes was 8.86 per 1000 person–years, and the rates rose to 10.00, 12.99, and 18.30 per 1000 person–years for those with diabetes onset 5, 6–10, and more than 10 years previously, respectively.
Of note, people with prediabetes (based on fasting blood glucose) did not have a significantly increased likelihood for dementia at any age, despite rates being slightly higher than in those without diabetes.
“It is possible that fasting glucose within the normal range does not adversely affect brain function,” suggest the researchers.
“Fasting blood glucose in those without diabetes has been shown to be only modestly associated with risk of vascular disease,” they add. “A certain threshold of high glucose levels may be necessary for hyperglycemia-induced brain injury.”
Cardiovascular risk, gauged using the Finnish Diabetes Risk Score, was not significantly associated with a further increase in the likelihood for developing dementia; neither were comorbid coronary heart disease nor heart failure.
However, having a stroke was associated with a significant additional increase in dementia risk. The rate of dementia was 5.18 per 1000 person–years in people with diabetes alone, compared with 24.32 per 1000 person–years in those with both diabetes and stroke, representing a more than twofold increase in an already elevated risk.
“These results highlight the need to address cardiovascular comorbidity in individuals with diabetes,” the researchers conclude.
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