Daytime-to-Nighttime Sleep Ratios and Cognitive Impairment in Older Intensive Care Unit Survivors.
Maya N Elías, Cindy L Munro, Zhan Liang
PMID 33644810WHAT IT FOUND
Older ICU survivors who slept more during the day than at night had worse cognitive flexibility.
This small study does not prove daytime sleep caused thinking problems.
Key findings
01Higher daytime-to-nighttime sleep ratios were associated with worse cognitive flexibility.
02Greater daytime sleep duration was associated with worse cognitive flexibility.
03Five participants (19%) had sleep ratios above 1, so they slept proportionally more during the day than at night.
STILL TO COME
How it was doneWhat they foundWhat it means for RNs
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What it does not show
The study was small and exploratory, with 26 participants analyzed from 30 enrolled. It used convenience sampling at one hospital and measured sleep and cognition at one time point, so it cannot show that daytime sleep caused worse cognitive flexibility. There was no pre-ICU cognitive assessment, so the researchers could not tell whether cognitive flexibility had already been impaired before ICU admission. Actigraphy may overestimate sleep duration and sleep efficiency compared with polysomnography. ICU delirium documentation was not included in the statistical models because the authors judged it unreliable for research. The sample was 22 White and non-Hispanic/Latino participants (85%), and all participants had been functionally independent before admission, so results may not apply to more diverse or more impaired older adults.
The easy way to misread this
Do not conclude that reducing daytime sleep after ICU discharge will improve cognitive flexibility. The study measured sleep and cognition at one time point in 26 older ICU survivors, so it shows association, not cause.