medwireNews: Results of a longitudinal study show that diabetes and poor glycemic control are associated with long-term cognitive decline among older people in the UK.
“Our findings suggest that interventions that delay diabetes onset, as well as management strategies for glucose control, might help alleviate the progression of subsequent cognitive decline over the long term,” say Wuxiang Xie (Imperial College London, UK, and Peking University Clinical Research Institute, Beijing, China) and study co-authors.
The team analyzed data from 5189 participants of the English Longitudinal Study of Ageing, who were aged a mean of 65.6 years and had normal cognitive function at baseline. These individuals underwent an average of 4.9 cognitive assessments over a mean 8.1 years of follow-up.
In all, 22.9% of participants were classified at baseline as having prediabetes, according to glycated hemoglobin (HbA1c) levels of 38.8–46.4 mmol/mol, and 8.6% had diabetes.
After adjustment for factors including age, sex, cholesterol, smoking, and baseline disease, Xie and colleagues found that a 1 mmol/mol increase in HbA1c was significantly associated with a higher rate of decline in global cognitive, memory, and executive function z scores.
Furthermore, patients with diabetes or prediabetes experienced a significantly greater reduction in cognitive scores over the follow-up period than those without. Compared with nondiabetic participants with HbA1c levels in the normal range (<38.8 mmol/mol), rates of global cognitive decline were increased by 0.031 standard deviations/year among those with diabetes and by 0.012 standard deviations/year for those with prediabetes. Memory, executive function, and orientation z scores also declined at a greater rate among participants with diabetes.
However, when the patients with diabetes were separated into two groups based on glycemic control, there was no significant difference in the rate of cognitive decline between patients with HbA1c levels of at least 53.0 mmol/mol versus those with levels below this cutoff.
“According to recommendations of the American Diabetes Association, maintaining an HbA1c level of less than 53.0 mmol/mol (7.0%) could help prevent diabetes-related microvascular complications,” write the researchers in Diabetologia.
They speculate that the lack of significant difference in the rate of cognitive decline between the two groups based on HbA1c level “might be attributable to diabetes treatment-related adverse events such as severe hypoglycaemia, which would result in fluctuations in blood glucose levels.”
And they add: “Although the underlying mechanisms remain to be elucidated, it is suggested that both hyperglycaemia and hypoglycaemia play important roles in diabetes-related cognitive decline.”
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