Sleep-Wake Disorders

Insomnia-Linked Short Sleep Duration Associated With Cognitive Impairment

Jessica Nye, PhD
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Insomnia with objective short sleep duration has been previously associated with adverse cardiometabolic health outcomes, as well as poorer cognitive performance in otherwise noncognitively impaired adults. However, studies demonstrating an increased prevalence of cognitive impairment in this insomnia phenotype are lacking.

Researchers from Penn State University College of Medicine found, in a population-based analysis, that cognitive impairment (CI) was associated with objectively measured short sleep duration. These results were published in Sleep.

Data (n=1741) from the Penn State Adult Cohort (PSAC) who were observed at the sleep laboratory between 1990 and 1999 were analyzed for this study. Participants were assessed with a comprehensive neuropsychological battery and evaluated over night for 8 hours monitored by a polysomnography.

Participants were aged mean 48.9 years, 46.6% were men, and 91.5% were White. Participants self-reported having normal sleep (n=899), poor sleep (n=453), and chronic insomnia (n=172). A total of 155 participants were found to have CI.

Self-reported sleep difficulty was significantly associated with age (P <.01), gender (P <.01), ethnicity (P =.03), body mass index (P <.01), hypertension (P <.01), physical and mental health problems (P <.01), and psychoactive medications (P <.01).

CI was significantly associated with all baseline characteristics (P <.01) except body mass index, physical and mental health problems, or psychoactive medications.

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Participants were stratified by objective sleep duration. Those who slept fewer than 6 hours per night had decreased CI (odds radio [OR], 2.06; 95% confidence limit [CL], 1.15-3.66; P <.05) compared with those who slept longer (OR, 2.18; 95% CL, 1.07-4.47; P <.05). Similarly, fewer hours asleep at night correlated with increased risk for possible vascular CI (OR, 1.94; 95% CL, 1.01-3.75; P <.05) compared with those who slept longer (OR, 2.33; 95% CL, 1.07-5.06; P <.05).

After adjusting for all possible cofounders, the investigators observed that short sleep duration (<6 hours per night) was significantly associated with CI (OR, 1.90; 95% CL, 1.22-2.95; P <.05).

Among participants who slept fewer than 6 hours per night, the individuals who self-reported normal sleep had a 4.5% projected rate of CI compared with 6.3% who reported poor sleep and 6.9% who reported insomnia.

Participants who self-reported poor sleep or chronic insomnia, but slept more than 6 hours per night were not associated with either CI (OR, 0.72; 95% CL, 0.30-1.76 and OR, 0.75; 95% CL, 0.21-2.71) or possible vascular CI (OR, 1.08; 95% CL, 0.42-2.74 and OR, 0.76; 95% CL, 0.16-3.57), respectively.

The major limitation of this study was that data collection occurred during a single 8-hour session at the sleep clinic, and therefore may not be indicative of the participants’ typical sleep patterns.

The study authors concluded that CI may be correlated with objective and not self-perceived short sleep durations and may aide in stratifying patients for increased risk for suboptimal brain health. However, future studies which include a more diverse study set and more sleep observations are needed to make a more robust link between these features.

Reference

Fernandez-Mendoza J, He F, Puzino K, et al. Insomnia with objective short sleep duration is associated with cognitive impairment: A first look at cardiometabolic contributors to brain health. Sleep. 2020;zsaa150. doi:10.1093/sleep/zsaa150