Sleep Sense by Katharina Lederle

Author:Katharina Lederle
Language: eng
Format: epub
Publisher: Exisle Publishing PTY Ltd.
Published: 2018-10-15T00:00:00+00:00

We are poor judges of our own sleepiness

While reading about cognitive impairment due to lack of sleep, has a thought along the lines of ‘Sleep deprivation doesn’t affect me at all’ crossed your mind? I ask because many people say this to me. And yes, there’s variability in how well people can cope with a lack of sleep (i.e. how soon and to what degree their cognitive performance will be affected). A small number of people are more resilient to the cognitive effects of sleep loss (genetics probably play an important role here), and you might be one of them — ‘the exception that proves the rule’ as the saying goes. For the majority of us, though, performance and productivity suffer if we get too little sleep. The ‘problem’ we have as humans is that we struggle to accurately judge our own level of sleepiness. What complicates matters is that while we can easily picture and describe a drunk person, we find it harder to do so for a sleep-deprived person.

There are two interesting research studies I would like to share with you in this context. The first investigated the effects of chronic sleep loss and how it impacts your performance. Here, they also looked at how you perceive your performance when sleep deprived. (I briefly touched on this topic in Chapter 1 when answering the question ‘How much sleep do I need?’ on p. 26.) Participants were divided into three groups who were allowed to sleep for, respectively, a maximum of four hours, six hours or eight hours a night for fourteen nights. A fourth group didn’t sleep at all for two nights. At specific times throughout the study, participants’ performance was measured objectively and they were asked to rate their own level of sleepiness at the same time. The results from the performance assessment showed that scores declined across the study period: the shorter the sleep time, the worse the scores. Those sleeping six hours or less for a prolonged time (in this case, fourteen nights) showed comparable performance degradation with those not sleeping at all for two nights.

What about the subjective sleepiness ratings? For the first four days, participants said that their sleepiness was increasing slightly, which matched their decline in performance. But then their ratings plateaued and participants said they did not get any sleepier — despite missing out on even more sleep. What was going on? Did they adapt to the lack of sleep? No, they didn’t. As I told you, when measured objectively performance continued to decline across the fourteen days. What had changed was their sense of their own sleepiness and their ability to judge it accurately.

The three key messages from this study are:

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Over time, even a small to moderate decrease in sleep duration can cause the same decline in performance as a whole night with no sleep.

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People don’t adapt to insufficient sleep. Many of us for one reason or another only sleep for six hours, which may be enough for some but the majority of us need at least seven hours.

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