Sleep quality plays a big role in how we feel and perform. Sleep quality must be balanced with sleep quantity. Nine, or even 10 hours, of very poor quality sleep can still leave you feeling fatigued. And, five hours of amazing quality sleep usually won’t keep fatigue at bay all day long either. In fact, when I was doing clinical work with hypersomniacs (people who feel sleepy all the time and sleep a lot), we would rebalance their sleep quality and quantity to help them experience shorter and more refreshing sleep, improving how they felt during the day.
In the sleep clinics, healthcare professionals use standardized indicators to determine sleep quality. The National Sleep Foundation’s indicators for good sleep quality in adults include:
- Falling asleep in 15 minutes or less
- One or less awakening of greater that 5 minutes per night
- Awake time of 20 minutes or less per night after falling asleep
- Sleep efficiency of 85% or greater (Sleep Efficiency = Time Spent Asleep/Time in Bed)
- REM sleep duration of 21 to 30% of total sleep duration
- Stage one sleep duration of 5% or less of total sleep duration
- Stage three sleep duration of 16 to 20% of total sleep duration
- Being able to get through the day without a nap
One popular tool used by sleep clinicians to assess sleep quality is the Pittsburgh Sleep Quality Index (PSQI) . The PSQI incorporates questions about many of the National Sleep Foundation’s sleep quality indicators and can provide clinicians with a good idea of how well their patient is sleeping in general. The PSQI is probably the most used and well-researched, but there are other sleep quality questionnaires with various strengths and weaknesses; they include:
- Sleep Quality Questionnaire (Kato, 2013)
- Restorative Sleep Questionnaire (Drake et al., 2014)
- Jenkins Sleep Scale (Jenkins et al. 1988)
- Sleep Condition Indicator (Espie et al. 2014)
- General Sleep Disturbance Scale (Lee, 1992)
- Maugeri Sleep Quality and Distress Inventory (Morrone et al., 2017)
- Sleep Disturbance Questionnaire (Espie et al., 2000)
- Karolinska Sleep Questionnaire (Nordin et al., 2013)
I use questionnaires, including the PSQI, in an operational context to assess general sleep quality of individuals, workgroups or a whole workforce. If I find that an individual’s sleep quality is generally poor, I will work with the person to figure out why and then provide sleep coaching to improve the person’s sleep quality. If I find that a workgroup or whole workforce is generally experiencing poor sleep quality, I will dig deep to find out why and then design solutions to help as many people as possible. These can include training, over-night sleep studies, work schedule improvements and other solutions targeted at the sources of poor sleep quality.
Most fatigue rules and regulations include some form of fitness for duty “test” based on sleep quantity. Most do not incorporate sleep quality into the test. This means that if you obtain 8 hours of sleep, regardless of quality, the test will show that you are fit for duty. Think back to the last time you slept for a total of 7 or 8 hours, but you miscalculated the timing of your caffeine and you consumed way too much before bed, or you drank too much alcohol, or the neighbours were partying loudly all night….you probably woke up a few times and your sleep quality was probably ruined. How did you feel the next day? I would guess you probably did not feel that great and you were probably fatigued. But if you got enough sleep, you would still pass the fitness for duty test and you might end up at work performing poorly during a safety critical or other situation where a mistake could cost you or the organization dearly. If the fitness for duty test would have flagged your poor quality sleep as a risk, you would not be in this situation. You and the organization would be safer and all sorts of risks would have been prevented. Fitness for duty tests must include assessments of sleep quality in addition to sleep quantity to be effective at reducing risk.
Notice that I stated “general” quite a few times in some of the preceding paragraphs. Most of the questionnaires I mentioned are designed to assess sleep quality over a period of time rather than for a specific moment in time. This means they cannot be used to assess sleep quality for a specific period of sleep. Our sleep quality can change from night to night and day to day. Just because you generally experience good sleep quality, it does not mean that last night’s sleep was good. Likewise, just because you generally experience bad sleep quality, it does not mean that last night’s sleep was bad. I have not been able to find a well-research and standardized assessment of sleep quality for a specific sleep period that could be used as part of a fitness for duty test. So how do you incorporate sleep quality into these tests? While we wait for researchers to design, validate and publish a questionnaire that assesses sleep quality for a specific period of sleep, here is what I suggest……just ask the person if their sleep was poor. Easy right?
Here is my logic. We can all usually tell when our last period of sleep was poor. We look back over the sleep and we use indicators similar to the National Sleep Foundation’s to determine sleep quality. That is, we look back at how long it took us to fall asleep, how many awakenings we had, the duration of the awakenings, how light our sleep felt (stage one sleep is considered light) and whether we feel like we need a nap to determine how poor the sleep was. This means it is pretty easy for most of us to know when our sleep was poor. A simple question like “On a scale of 1 to 5, where 5 is terrible sleep quality and 1 is no indication of poor sleep, how poor was the quality of your last sleep period?” within a fitness for duty test would increase the accuracy of the results. More importantly, because subjective sleep quality is positively linked to objective performance the test would also reduce risk.
I framed the sleep quality question strategically. I did not ask for a simple rating of sleep quality from good to bad. I specifically asked about poor sleep, not good sleep. This is because good sleep quality is more difficult for us to recognize. If you don’t experience any awakenings during your sleep or a lot of light sleep, 8 hours of poor quality sleep, perhaps due to arousals, could feel the same as 8 hours of good quality sleep. In other words, if you feel that your sleep quality was poor it probably was; but if your sleep quality felt good, it could have been bad or good. Within a fitness for duty test, asking about poor quality sleep would provide more accurate results, whereas asking about good quality sleep would probably not.
To improve upon the rules and regulations you have to follow when determining if someone is too fatigued to work, remember to incorporate sleep quality into your fitness for duty test and ask specifically about poor sleep.
 Ohayon, M., Wickwire, E., Hirshkowitz, M., Albert, S., Avidan, A., Daly, F., Dauvilliers, Y., Ferri, R., Fung, C., Gozal, D., Hazen, N., Krystal, N., Lichstein, K., Mallampalli, M., Plazzi, G., Rawding, R., Scheer, F., Somers, V., & Vitiello, M. (2017). National Sleep Foundation’s sleep quality recommendations: First Report. Sleep Health, 3, 6-19.
 Buysse, D., Reynolds, C., Monk, T., Berman, S., & Kupfer, D. (1988). The Pittsburgh Sleep Quality Index: A new instrument for psychiatric practice and research. Psychiatry Research, 28, 193-213.
 For a review of questionnaires used in the assessment of insomnia, including sleep quality questionnaires, see: Ali, R., Zolezzi, M., & Awaisu, U. (2020). A systematic review of instruments for the assessment of insomnia in adults. Nature and Science of Sleep, 12, 377-409.