Insomnia With Short Sleep Linked to Cognitive Impairment

Insomnia with objective short sleep duration is associated with a significantly increased risk of cognitive impairment (CI), particularly as it relates to cardiometabolic health, new research suggests.

Results of a population-based analysis show that participants who reported poor sleep or chronic insomnia and who objectively slept less than 6 hours per night had a twofold increased risk for CI.

The findings suggest that insomnia with objective short sleep duration is a more severe phenotype that is associated with cardiovascular, cerebrovascular, and neurocognitive disease, according to the researchers. The findings also indicate that objective sleep measures may reflect a patient's insomnia severity and phenotype.

"This is the first study to show that adults who complain of insomnia and sleep objectively fewer than 6 hours in the lab have a twofold increased prevalence of mild cognitive impairment, particularly cognitive impairment associated with vascular contributors such as stage 2 hypertension, type 2 diabetes, heart disease, or stroke," Julio Fernandez-Mendoza, PhD, associate professor of psychiatry at Penn State University College of Medicine in Hershey, Pennsylvania, told Medscape Medical News.

The research was published online September 24 in Sleep.

Highly Prevalent

The prevalence of insomnia symptoms in the general population may be as high as 30%, and approximately 15% of the general population has chronic insomnia.

Previous research has established an association between insomnia and psychiatric disorders, but fewer studies have examined the association between insomnia and cognitive impairment.

Furthermore, many studies that have analyzed the relationship between sleep and cognitive impairment have relied on self-reported measures of sleep, rather than objective measures.

For the study, researchers examined data from the Penn State Adult Cohort, which was a random, population-based sample of 1741 adults. Each participant spent one night in the sleep laboratory, during which he or she underwent 8 hours of polysomnography.

Participants also completed a questionnaire about sleep disorders, physical and mental health status, and substance use. They reported having normal sleep, poor sleep, or chronic insomnia.

The investigators obtained each participant's clinical history, including mental and physical health conditions. Participants also underwent a battery of neuropsychological tests, including the Mini-Mental State Examination, the Symbol Digit Modalities Test, and the Trail Making Test.  

The analysis included 1524 participants. The study population had a mean age of 48.9 years. Approximately 47% of participants were men, and about 92% were non-Hispanic Whites.

A total of 155 participants (10.2%) had CI. Overall, 899 participants (59%) reported normal sleep, 453 (30%) reported poor sleep, and 172 (11%) reported chronic insomnia.

Need for Objective Assessment

Poor sleep and chronic insomnia were not significantly associated with CI or possible vascular cognitive impairment (pVCI). However, objective short sleep duration was significantly linked to CI (odds ratio [OR], 1.90) and marginally associated with pVCI (OR, 1.53).

Participants with self-reported poor sleep or chronic insomnia who slept less than 6 hours had a significantly increased risk of CI (OR, 2.06 and 2.18, respectively), as well as increased risk of pVCI (OR, 1.94 and 2.33, respectively), compared with participants with self-reported normal sleep who objectively slept 6 hours or more (ie, the reference group).

But participants who reported poor sleep or chronic insomnia and slept objectively more than 6 hours did not have a significantly increased risk of CI (OR, 0.72 and 0.75, respectively) or increased risk of pVCI (OR, 1.08 and 0.76, respectively), compared with the reference group.

In addition, those who reported normal sleep and slept objectively less than 6 hours had a higher prevalence of cognitive impairment compared with the reference group. However, this association was not statistically significant after controlling for potential confounding factors.

"Demographic and clinical factors, such as other physical and mental health conditions, may account for some of the observed association in these short sleepers without insomnia symptoms," said Fernandez-Mendoza. The finding "also suggests that there is a significant subset of noncomplaining, natural short sleepers who do not have cognitive sequelae."

Patients with insomnia and vascular risk factors or diseases should undergo objective sleep and cognitive evaluation, he added. To rely solely on these patients' subjective reports would be inappropriate.

Patients with mild cognitive impairment who complain of insomnia should undergo a sleep study to examine the potential contribution of sleep apnea and other sleep disorders and to identify insomnia associated with objective short sleep, which may require specific treatment approaches, he added.

"These data indicate that patients with insomnia and objective short sleep duration, who are more likely to have cardiometabolic conditions and mild cognitive impairment, may require more targeted treatments, such as the combination of cognitive-behavioral and pharmacological therapies, when addressing the clustering of impairing conditions," said Fernandez-Mendoza.

The study was funded by the American Heart Association and the National Heart, Lung, and Blood Institute within the National Institutes of Health. Fernandez-Mendoza received a research grant from the American Heart Association for this study. He had no other disclosures.

Sleep. Published online September 24, 2020. Abstract

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Cite this: Insomnia With Short Sleep Linked to Cognitive Impairment - Medscape - Oct 19, 2020.