The eighth variable that I will be manipulating across a two week period to examine its impact on sleep is length of time in bed. I will be seeing if spending too long in bed is harmful to sleep quality, and if restricting time in bed is a good way to improve it.
I will discuss what my data shows, how easy or difficult I found this strategy to implement, and what previous research says. These three factors will be combined for an overall score and grade on how effective sleep restriction is at improving the quality of our sleep.
IF I AM ALREADY TIRED, SHOULDN’T I SPEND MORE TIME IN BED?
It’s all over the media these days: The majority of people are sleep deprived. They say that we need to prioritise sleep, and get more of it. They also say that we used to sleep more, and blame our lack of sleep for a multitude of problems, from more accidents, our lack of productivity, greater rates of depression and anxiety, and even weight gain.
What they don’t tell you is how to get more sleep. The obvious answer would be to spend more time in bed, or get to bed earlier. This may help for some people, especially those who do not experience any difficulties in getting to sleep at the start of the night or staying asleep during the night.
For people with insomnia however, spending more time in bed awake is potentially the worst thing that they can do, especially if it leads to them becoming more worried or frustrated about their sleep difficulties. People with insomnia are already focusing on sleep too much, and are also usually going to bed before their body is ready for sleep each night.
If you are having difficulties with getting to sleep at the start of the night, even though it is quite counter-intuitive, waiting up until you feel sleepy before going to bed is one of the best ways to ensure that you will fall asleep quickly once you are in bed.
If you are having difficulties with waking up during the night, one of the quickest ways to reduce the amount of time that you spend awake during the night is to reduce your time in bed.
WHAT IS SLEEP RESTRICTION?
It sounds pretty scary to people that are already not sleeping enough, but sleep restriction doesn’t aim to reduce the amount of time that you sleep each night at all. What it is actually aiming to do is reduce the amount of time that you spend in bed awake each night. For this reason, at the Melbourne Sleep Disorders Centre where I work we call it bed restriction, not sleep restriction.
Let’s say that you feel that you need 7 hours of sleep on average, but are currently only getting 6 hours of sleep per night. You are wanting to get that extra hour, so you start spending 9 hours in bed instead of your usual 8 hours. By doing this, you expect your total sleep time to improve, but instead it stays about the same. Worse still, you are now spending nearly 3 hours in bed awake each night rather than the 2 hours that you were previously. Your sleep efficiency (percentage of time in bed spent sleeping) has decreased from 75% to 66.67% and now the nights seem to be dragging on for ages!
With sleep restriction what we want to do is the opposite. 85-90% is considered an ideal sleep efficiency to aim for, so if you are currently sleeping 6 hours per night we would actually want to cut down your time in bed to between 6.5 and 7 hours per night. This will make you more tired initially, but very quickly your sleep efficiency would reach the desired 85-90% range, whilst still obtaining 6 hours of sleep per night. Even better, you are now only awake for 30-60 minutes in bed per night, rather than 2-3 hours, which will help make the night go quicker and give you a better quality sleep.
Once you are sleeping better and spending less time in bed awake each night, we can then slowly increase your time in bed again, by 15 minutes per night every 1-2 weeks. As long as your sleep quality remains high, you might even be able to increase your total sleep time until you are reaching that 7 hours of sleep per night.
For the first week, I tried to show the negative impact of spending longer than usual in bed. Because I had to get up for work and am so used to waiting until I feel sleepy before going to bed this was actually quite hard, but I managed to spend nine hours in bed on average. 7 hours and 45 minutes was the shortest time in bed the first week, and 9 hours and 30 minutes was the longest.
For the second week, I tried to implement a sleep restriction routine. I managed to restricted my average time in bed to under 7 hours. The longest time in bed on any night for the second week was 8 hours and 10 minutes, and the shortest was 5 hours.
Comparison: Too much time in bed vs Sleep restriction
Based on my sleep diary data, I managed to sleep 8 hours a night the first week, which was an hour and 28 minutes more than the second week. I also managed to get to bed by 11:01pm during the first week, which is more suitable to my work week than the 12:39am bedtime the second week. This is where the good news stops however.
By implementing sleep restriction during the second week I fell asleep in under 10 minutes, 13.5 minutes quicker than the first week. I only awoke once per night rather than twice, and spent 12 minutes awake each night, rather than 38 minutes the first week. My sleep quality was a full point higher (4.29/5) during sleep restriction than it was when I was spending too long in bed (3.29/5). My sleep efficiency was also 6% higher with sleep restriction (94.81%) than it was the first week (88.78%).
Based on my data, after only a week of sleep restriction, my sleep was getting right back on track to where it was before the silent meditation retreat. I was feeling more tired by the end of the work week, especially after only 4 hours and 40 minutes of sleep on the Wednesday night, and this was evident by my turning to caffeine on the Wednesday, Thursday and Friday morning. The Thursday night was potentially the best sleep that I’d had in a month though, thanks to the positive impact of increased sleep pressure.
Based on the Misfit Ray data, the depth of my sleep was way better the second week during sleep restriction than it was the first week when I was spending too long in bed.
Let’s compare the Thursday night from the first week to the Thursday night from the second week. Even though the Misfit Ray didn’t pick up on any awakenings during the first Thursday (Apr 28 – 27/4/17 on the sleep diary), my restful:light sleep ratio was 0.83. The following week (May 05 – 4/5/17 on the sleep diary) I didn’t have any awakenings on the sleep diary or the Misfit data, and my objective restful:light sleep ratio was 2.69, which is incredible.
Even though I was in bed for 35 minutes less the second Thursday night, I was able to obtain nearly 2 hours more restful sleep than during the first Thursday night. Sleep restriction = better objective sleep quality.
IS SLEEP RESTRICTION A GOOD SLEEP STRATEGY?
IS IT EFFECTIVE?
Yes. Only being in bed for the amount of time that I need to sleep is one of the most effective ways for me to improve my sleep quality and ensure that it remains good over time. As long as I am going to bed at the right time for my body clock, keeping these times fairly consistent from night to night and that I am trying to wind down and relax before sleep, this strategy is one of most effective for me.
I therefore give the effectiveness of this strategy a 23/25.
CAN IT BE APPLIED?
For me, yes. But the downside of sleep restriction is that it temporarily increases daytime somnolence and reduces vigilance in the initial phases of treatment (Kyle et al., 2014). Adherence to sleep restriction may also be difficult to obtain from individuals who are already concerned about daytime consequences of insomnia (Riedel & Lichstein, 2001).
If there is excessive daytime sleepiness, caution should be given regarding driving or operating machinery, and some time off work may be required. However, this increase in sleepiness prevents individuals with insomnia from lying in bed ruminating or worrying, and it has been shown to significantly improve sleep initiation and increase overall sleep quality (Lieberman & Neubauer, 2007).
I therefore give the applicability of this strategy a 13/25.
IS IT SCIENTIFIC?
Sleep restriction is considered a highly efficacious and effective treatment for insomnia (Morin et al., 2006). It was initially conceived of in the 1980s and involves limiting the time in bed to an individual’s average subjective daily amount of sleep (Spielman et al., 1987). By only spending enough time in bed for sleep, sleep restriction temporarily induces sleep deprivation, which increases the homeostatic drive for sleep, decreases sleep fragmentation and consequently improves sleep efficiency (Vitiello, 2007). However, it is important to prescribe the sleep at a constant time that is in line with an individual’s circadian rhythms and lifestyle (Ebben & Spielman, 2009).
Sleep restriction is similar to relaxation in reducing time taken to get to sleep and time awake during the night across the treatment period, and more effective in maintaining these improvements by a 3-month follow-up assessment (Friedman et al., 1991). After 12 months follow-up in another study, time awake during the night had gotten worse since post-treatment with relaxation but continued to improve with sleep restriction (Lichstein et al., 2001). Another study of CBT-I found that sleep restriction adherence was one of the two best predictors of ongoing sleep improvements 12 months later (Harvey, 2002). Consequently, as long as adherence issues are addressed, sleep restriction can produce dramatic and robust improvements in insomnia symptoms.
I therefore give the science of this strategy a 45/50.
Overall, sleep restriction as a way to sleep better gets a score of 23/25 + 13/25 + 45/50 =
81/100: High Distinction
WHAT I RECOMMEND
- Complete a two week sleep diary or use an activity tracker to get a baseline measure of your sleep.
- Figure out your average total sleep time.
- If this is under 5 hours per night, try to spend 5 hours and 30 minutes in bed per night.
- If it is over 5 hours, add 30 minutes to your total sleep time for your initial time in bed prescription.
- Figure out what time you would like to get out of bed each morning. Set your alarm for this time each day for the next 1-2 weeks.
- Minus your time in bed prescription from your wake time to figure out your to bed time.
- Go to bed each night around your to bed time, as long as you are feeling sleepy. If you are not sleepy yet, do something to try to wind down and relax, and then go to bed once sleepy.
- After 1-2 weeks, if your sleep efficiency is:
- less than 85% = cut down your time in bed by an extra 15 minutes the following week.
- between 85-90% – keep your time in bed the same
- over 90% – increase your time in bed by 15-30 minutes the following week.
This is the most scientific way that you can figure out what is the right amount of time in bed for you. If these recommendations are too general or confusing, you can always send me your two weeks of sleep data, and I will score up your sleep and give you some specific and tailored recommendations for what you can do to improve it. For more information, check out my Personalised Sleep Reports services.
Dr Damon Ashworth