January 25, 2018
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Poor glucose control increases risk for cognitive decline

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Wuxiang Xie
Wuxiang Xie

Rising HbA1c levels are linearly associated with a subsequent cognitive decline in memory and executive function, regardless of diabetes status, according to findings published in Diabetologia.

“The association between diabetes and dementia has been well-documented; however, the association between diabetes and cognitive decline is less well-studied,” Fanfan Zheng, PhD, of the Brainnetome Center, Institute of Automation, Chinese Academy of Sciences in Beijing, and colleagues wrote. “Cognitive decline occurs over a long period prior to dementia, and the trajectory of cognitive decline, which consists of several assessments of cognitive function, is important for evaluating and monitoring the progression of cognitive deterioration.”

Zheng and colleagues analyzed data from 5,189 adults participating in waves 2 through 7 (2004-2015) of the English Longitudinal Study of Aging (ELSA), a prospective cohort of adults aged at least 50 years living in England (mean age, 66 years; 55.1% women). Participants provided blood samples to measure HbA1c and completed memory assessments and underwent testing of executive function and orientation at baseline and every 2 years, and researchers generated a composite global cognitive z score for each participant.

Within the cohort, 22.9% had prediabetes and 8.6% had diabetes. The mean HbA1c was 5.57%, ranging from 3.6% to 13.7%. Mean follow-up time was 8.1 years, and participants underwent a mean of 4.9 cognitive assessments.

Researchers observed longitudinal associations between HbA1c level and the rate of change in cognitive decline. Each 1-mmol/mol increment in HbA1c was associated with a –0.0009 standard deviation (SD) per year decline in global cognitive z score (95% CI, –0.0014 to –0.0003), a –0.0005 SD decline in memory z score (95% CI, –0.0009 to –0.0001) and a –0.0008 SD per year decline in executive function z score (95% CI, –0.0013 to –0.0004). There was no link observed between HbA1c and orientation z score, according to researchers.

Researchers also found that the cognitive scores of patients with diabetes declined at a greater rate vs. those who did not have diabetes., The rate of global cognitive decline associated with prediabetes was –0.012 SD per year (95% CI, –0.022 to –0.002) compared with those without diabetes, whereas the rate of global decline associated with diabetes was –0.031 SD per year compared with those without diabetes (95% CI, –0.046 to –0.015; P for trend < .001). Memory, executive function and orientation z scores also declined at a greater rate for patients with diabetes vs. those without diabetes, according to researchers.

“Management strategies for glucose control might help to alleviate the progression of subsequent cognitive decline over the long term,” Wuxiang Xie, PhD, of the School of Public Health at Imperial College London, told Endocrine Today. “We think there must be some underneath mechanisms that we don’t understand yet, and it is worth trying to find new markers to study those mechanisms.” – by Regina Schaffer

For more information:

Wuxiang Xie , PhD, can be reached at School of Public Health, Imperial College London, Department of Epidemiology and Biostatistics, St Mary's Campus, Norfolk Place, W2 1PG, London, United Kingdom; email: w.xie@imperial.ac.uk.

Disclosures: The authors report no relevant financial disclosures.