New Study Shows We May Not Be Aware of Decreased Cognitive Abilities Due to Poor Sleep

According to Brigham and Women's Hospital researchers.

waking up

Photo via

We’ve all been there—sleep-deprived and barely functioning while double fisting extra large caramel mocha iced coffees from the Dunkin’s down the street. Even though we all know how important sleep is, there’s just never any time to get enough of it.

So we push on. Just one more triple shot Americano and we’ll be good to go—or so we thought. According to a new study from the Brigham and Women’s Hospital published in the Proceedings of the National Academy of Sciences, our bodies are pretty great at adapting to a plethora of different situations, but a lack of sleep is not one of them.

The study, which placed nine healthy participants on a 20-hour day, restricting them to 4.67 hours of sleep and 15.33 hours of wakefulness, looked at the impact of chronic shortened sleep separate from any extended wakefulness. Meaning, researchers were trying to detect if the decline in functions we so readily see from lack of sleep is due to restricted sleep or from being awake for an extended amount of time. On a regular 24-hour day, that time frame would translate to a little over five hours of shut eye and 15 hours of wakefulness, which is not considered extended wakefulness. To compare, eight healthy controls were allowed 6.67 hours of sleep and 13.33 hours of wakefulness on a 20-hour day, translating to the recommended eight hours of sleep in a regular 24-hour day.

The results?

Participants with restricted sleep not only had an increase in attention lapses and doubled neurobehavioral reaction time, compared to their control counterparts, but they did not notice the impairments and continued to worsen in cognitive tasks over the 32-day protocol. In short: Not only could they not adapt to sleeping less, they couldn’t identify their own decrease in cognitive function.

“We’ve shown that sleep in itself is important,” Elizabeth Klerman, a doctor from the Division of Sleep and Circadian Disorders Department of Medicine at Brigham and Women’s and a senior author on the study, said in a press release. “We found that chronic short sleep duration, even without extended wakefulness, resulted in vigilant performance impairments. People cannot learn to live on insufficient sleep and they may not be aware of their reduced cognitive abilities resulting from it.”

So when it comes time to turn out the lights, actually do so. Everything else can wait until morning.