Abstract
AimWe aimed to detect the individual and combined effect of glucose metabolic components on cognitive function in particular domains among older adults.MethodsData of 2,925 adults aged over 60 years from the 2011 to 2014 National Health and Nutrition Examination Survey were analyzed. Individuals’ cognitive function was evaluated using the Digit Symbol Substitution Test (DSST), the Animal Fluency Test (AF), the Consortium to Establish a Registry for Alzheimer’s Disease Immediate Recall (CERAD-IR), and CERAD Delayed Recall (CERAD-DR). Participants’ glucose metabolic health status was determined based on fasting plasma glucose, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), glycated hemoglobin (HbA1c), and 2-h postload glucose. Linear regression models were used to delineate the associations of cognitive function with individual glucose metabolic component and with metformin use. Logistic regression models were performed to evaluate the associations of cognition with the number of glucose metabolic risk components.ResultsCERAD-IR was significantly associated with HOMA-IR and insulin. HbA1c was related to all the cognitive tests except AF. Among participants without obesity, HOMA-IR and insulin were both negatively associated with CERAD-IR and CERAD-DR. Odds of scoring low in DSST increased with the number of glucose metabolic risk components (odds ratio 1.94, 95% confidence interval [CI] 1.26 to 2.98). Metformin use was associated with better performance in DSST among diabetes patients (β = 4.184, 95% CI 1.655 to 6.713).ConclusionsOur findings support the associations of insulin resistance and glycemic level with cognitive function in key domains, especially among adults without obesity. There is a positive association between metformin use and cognition.
Highlights
The prevalence of type 2 diabetes has increased remarkably over the past decades [1], imposing huge burden on healthcare expenditure
We found significant associations of 2-h postload glucose (2h-PG) with scores of CERAD-IR, CERAD-DR, and Digit Symbol Substitution Test (DSST) in Model 1, but such associations were only maintained for CERAD-DR (b = −0.070, 95% confidence intervals (CIs) −0.134 to −0.005) in the fully adjusted model
In the linear regression analysis (Table 4), we found significant associations of metformin use with better language fluency, as evaluated with Animal Fluency Test (AF) (b = 1.362, 95% CI 0.270 to 2.454), and better executive function, as evaluated by DSST (b = 7.406, 95% CI 4.373 to 10.440)
Summary
The prevalence of type 2 diabetes has increased remarkably over the past decades [1], imposing huge burden on healthcare expenditure. With respect to risk factors for cognitive impairment among patients with diabetes, glucose metabolic components, including glycemic level and insulin resistance, have attracted much attention. Regarding disorders of insulin homeostasis, converging evidence has shown that insulin resistance or consequent hyperinsulinemia is related to poor cognitive performance [6]. Most of these studies focused on the relationship of global cognitive function with glycemic level or insulin homeostasis separately, and few have systematically described individual and combined associations of glucose metabolic components with cognition in particular domains, such as learning, memory, processing speed, executive function, and language
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