People with diabetes and prediabetes who have lower sleep efficiency — a measure of how much time in bed is actually spent asleep — show reduced cognitive function compared to those with better sleep efficiency, according to a new study published in the journal Acta Diabetologica.
“The cognitive effects of poor sleep quality are worse for this population, which we know is already at risk for developing cognitive impairment as a result of having diabetes,” said Dr. Sirimon Reutrakul, associate professor of endocrinology, diabetes and metabolism in the University of Illinois at Chicago College of Medicine and corresponding author of the paper.
In earlier research, diabetes has been associated with cognitive impairment and an increased risk for dementia. In addition, some studies have suggested that sleep disturbances, which are common among people with diabetes, may also be linked to cognitive impairment.
For the study, the researchers looked at the relationship between sleep and cognitive function in participants with abnormal glucose tolerance. This included patients with impaired glucose tolerance indicative of prediabetes, as well as patients with clinically diagnosed diabetes.
The study included 162 participants: 81 with Type 2 diabetes and 81 with prediabetes. The average age of the participants was 54.8 years.
Sleep duration and sleep efficiency — a measure of how much time in bed is spent sleeping and an important indicator of sleep quality — were calculated for each participant through seven-day actigraphy recordings. An actigraph is a device worn on the wrist that measures motion. In sleep studies, periods of sleep are considered those in which the actigraph records periods of time with no motion.
Cognitive function was evaluated via a questionnaire known as the Montreal Cognitive Assessment, or MoCA. All participants were assessed for obstructive sleep apnea — a sleep disorder where sleep is interrupted when the airway becomes restricted and breathing temporarily stops.
The findings show that the average sleep duration was six hours per night, and the average sleep efficiency was 82.7 percent (meaning that 82.7 percent of time spent in bed was spent in sleep).
The researchers found that the duration of sleep, as well as the severity of diagnosed obstructive sleep apnea, did not appear to affect cognitive function as measured by MoCA.
However, better sleep efficiency was tied to better cognitive function scores for participants with diabetes and prediabetes. The researchers also found that having diabetes in itself was linked to lower cognitive function scores.
“Our study shows that lower sleep efficiency is independently associated with lower cognitive function in patients with abnormal glucose tolerance,” said Reutrakul. “Further studies should look at whether helping these patients sleep better could improve cognitive function.”