I’m now in week 6 of sleep restriction and I have to say my sleep is getting better. I mostly sleep for 5.5 hours a night. When I started it was 3.
My sleep window starts between 11 and 12 and ends at 6. I was having trouble staying awake until midnight, and by allowing myself to go to bed at 11 (or soon after that) I can fall asleep faster.
But the last couple of nights, I’ve woken up in the middle of the night and had trouble falling back to sleep. I have no idea why I’m waking up. Do you have any tips for staying asleep?
Chantal’s sleep has improved a lot with sleep restriction therapy. She’s nearly doubled her sleep time, going from 3 to 5.5 hours of sleep a night. But now her sleep is interrupted with wake-ups. If she wants to stay asleep at night, she needs to improve her sleep efficiency. Regardless of whether you’re going through sleep restriction therapy, it’s helpful to understand this concept if you want to improve your sleep.
Why Sleep Restriction?
Sleep restriction therapy is an insomnia treatment that consolidates sleep by first limiting time in bed to the actual amount of time a person is sleeping. (That chunk of time is sometimes called the sleep window.) Most insomnia sufferers experience sleep deprivation in the first week or two. But studies show that fairly soon this leads to deeper, more efficient sleep. In the process you gradually enlarge your sleep window until you’re sleeping efficiently and as much as you can.
Sleep Efficiency—What It Is and Why It Matters
Sleep efficiency refers to the percent of time you’re actually sleeping when you’re lying in bed at night. The sleep of good sleepers is highly efficient (i.e., they’re asleep 90% or 95% of the time they’re in bed). They drop off quickly and sleep soundly through the night.
If you have insomnia, your sleep is probably inefficient, interrupted by patches of wakefulness. You may only be sleeping 70% or 75% of the time you’re in bed.
Restricting time in bed will help you (1) fall asleep faster and (2) cut down on sleeplessness in the middle of the night. In other words, your sleep will become more efficient—and efficient sleep is typically sounder and more refreshing.
Calculating Sleep Efficiency
If you go through sleep restriction therapy, you’ll calculate your sleep efficiency at the end of each week. Here’s how to make the calculation:
- Sleep Efficiency (SE) equals Total Sleep Time (TST) divided by prescribed Time in Bed (TIB) multiplied by 100.
- The formula looks simpler using abbreviations and symbols: SE = TST ÷ TIB X 100.
Increased sleep efficiency is good in and of itself. But during sleep restriction, your sleep efficiency is also used to establish your sleep window for the following week:
- A high sleep efficiency suggests it’s time to enlarge your sleep window.
- A low sleep efficiency (anything less than 80%) suggests a need to tighten up your sleep window until your sleep is solid again.
Reducing Wake-Ups at Night
Chantal says she’s averaging 5.5 hours of sleep a night but that she’s now having wake-ups. The problem may lie in her variable bedtime (between 11 p.m. and midnight) and the amount of time she’s spending in bed. It’s easy to see if we do the math:
If on most nights she goes to bed at 11 p.m. and gets up at 6 a.m. (for a total of 7 hours in bed), her sleep efficiency may be low: 5.5 ÷ 7 X 100 = 78.6%. Inefficient sleep is characterized by patches of sleeplessness.
In contrast, if on most nights Chantal restricts her time in bed to 6 hours (as would occur if she delayed her bedtime until midnight and got up at 6 a.m., or set her sleep window from 11:30 p.m. to 5:30 a.m.), her sleep efficiency will probably be high: 5.5 ÷ 6 X 100 = 91.7%. She can increase her time in bed by 15 or 20 minutes the following week.
Tightening up her sleep window now may enable Chantal to maintain consolidated sleep as she gradually increases her time in bed.
If you’re going through sleep restriction, don’t make the mistake of enlarging your sleep window too fast too soon. At the end of each week, calculate your sleep efficiency and adjust your time in bed accordingly. Slow and steady wins this race.
For those who simply want to cut down on middle-of-the-night wake-ups, try spending less time in bed.