The science is clear. Working age adults should sleep at least seven hours every night to protect their health. Did you get at least seven hours of sleep last night? It is estimated that one-fifth to one-third of adults had less than seven hours of sleep last night. But did you know, for example, that if you sleep less than seven hours, or longer than nine hours, you also perform worse?
The science of sleep and performance
Sleep researchers have tested many links between sleep and time of day, and how well we perform, often in lab studies. As researchers gain access to data from activity clocks, research in sleep is getting better and better. All of a sudden, you can study lots of people living their regular lives, and not just the shards of information you can get in a lab environment or with other cumbersome measurement methods. One also avoids being dependent on subjective estimates of sleep schedules that we know are not entirely accurate. Until a few years ago, the largest study on sleep and performance had 76 participants. In 2017, a study was published where 31,000 participants were studied for 18 months (there will be more than 3 million nights to analyze).
Drowsy driving
Sleep deprivation of various kinds affects our ability in many different ways. We react more slowly, are less productive, and less creative. This is noticeable, for example, when driving a car. If we compare the risk of accidents while driving with how we drive when we have slept for at least 7 hours, the risk of accidents increases already between 6 and 7 hours of sleep. If we have slept between 5-6 hours, the risk of accidents double, and if we sleep less than that, the risk of accidents continues to rise significantly.
Having slept between 4-5 hours has the same increase in risk of accident as driving under the influence of alcohol (BAC 0.8%) . The same logic can be used when talking about performing at work as well. If your sleep has been lacking, your work will appear as if it was done by a drunken person. The study I quoted earlier is about sleep during the previous 24 hours. If you have slept a bit too little, but several nights in a row, it has similar effects.
Sleep duration, circadian rhythm & performance
The sleep data that was collected from the activity clocks (which was of a simpler kind than, for example, the one NudgeLabs uses) was linked to how quickly and correctly the participants typed on their keyboards in their everyday lives. The researchers illustrate clearly how our performance follows our circadian rhythm:
- In the morning our performance improves rapidly
- High performance is maintained until late during the afternoon
- Our performance declines rapidly during the late afternoon, and is steadily deteriorating all evening
- Performance deteriorates further during the night until the worst point of the day just before morning
Of course, the time of day and performance is affected by whether you are a morning person or evening person - it differs up to three hours between different groups. The people who are the most alert in the morning performed at their worst at 4 AM, those in the middle around 5 AM, while those with the latest sleep habits performed at their worst at 6-7 AM.
Everything above is about typical patterns when we sleep as we usually do. How important is it then to go to bed regularly or sleep a little shorter just a few nights from time to time? Going to bed an hour later than usual (or more) affects performance - but not going to bed earlier. Too little sleep (less than six hours) in a single night clearly affects performance. Sleeping too little for two nights in a row affects it even more.
Get better sleep to increase performance
Getting better sleep can be easier said than done. One step towards better sleep could be to simply start prioritizing sleep. Sometimes we seem to forget that we are actually an animal species. We are so modern and civilized that we almost seem to expect that we shouldn't have to take into account our biological conditions. It seems old-fashioned to hand out sleep advice like "get enough sleep" or "have a regular sleep habit", and no one wants to be old-fashioned. It's easier not to be, and not have to worry.
Remember that this is not a call from your mother, your doctor or even the world's most renowned sleep researchers. It is your body telling you what it needs. We can listen to the body and prioritize things that are good for us as often as we can - so sleep at least 7 hours per night and at the same time as many nights in a row as you can. Make plans so that you have the opportunity to get at least seven hours every night and you will increase your performance in a relatively simple and very comfortable way!
Advice for sleep deprivation
If you are reading this and have trouble sleeping, I know that it can be worrying to read about these things. At the same time, I think you more often than others notice how sleep is related to a lot of other things, such as focus and performance. Maybe you are already motivated to improve your sleep. My advice to you is to do what you can for your sleep, and to protect your health and productivity in all the other ways that are at your disposal:
- Eat better food
- Get some exercise
- Take breaks during the day
- Don't spend too much or too little time in bed
- Get some daylight every day
- Prioritize regular sleep as much as possible
- Relax a bit in the evening before you go to bed
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