High cortisol linked to age-related cognitive decline in older Type 2 diabetics
MedWire News: High morning levels of the glucocorticoid cortisol in elderly individuals with Type 2 diabetes are associated with greater estimated cognitive decline, say researchers.
“People with Type 2 diabetes are at increased risk of cognitive impairment but the mechanism is uncertain,” write Rebecca Reynolds (University of Edinburgh, UK) and co-workers.
However, they add: “Increasing evidence supports a link between elevated plasma glucocorticoids and cognitive dysfunction.”
To assess whether high levels of morning cortisol are associated with cognitive decline, the team carried out a cross sectional study of 1066 Scottish individuals with Type 2 diabetes who were aged 60–75 years.
The researchers evaluated cognitive abilities including memory, nonverbal reasoning, information processing speed, executive function, and mental flexibility, from which they derived a general cognitive ability factor (g). Lifetime cognitive change was estimated from adjustment for scores on a vocabulary test used to assess prior intelligence.
Plasma cortisol levels varied from below 591 nmol/l in the first quartile to above 841 nmol/l in the fourth quartile.
High fasting cortisol level was not associated with current g score or performance in individual cognitive domains.
But high morning cortisol concentration was linked to increased estimated cognitive decline in g and working memory and processing speed, independently of metabolic variables, mood, education, and cardiovascular disease.
“It may be that people with diabetes are more susceptible to the effects of stress on plasma cortisol such that repeated cortisol elevations damage the hippocampus,” suggest Reynolds et al.
“Our own studies of impaired habituation of cortisol responses to venepuncture would be consistent with activation of the hypothalamic-pituitary-adrenal axis from higher centers in Type 2 diabetes,” they add.
The team concludes in the journal Diabetes Care: “Further investigation is required to determine the direction and nature of this relationship, which, if causal, would support the use of therapeutic strategies to lower cortisol action to ameliorate cognitive decline in individuals with Type 2 diabetes.”
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By Helen Albert