We are all (hopefully) born with the ability to sleep, but we aren’t necessarily born knowing when and how to achieve optimal kip. In order to sleep well, our body clock has to be set to fall asleep at the same time that our natural sleep drive reaches a high – and when we struggle to drift off, many of us instinctively go to bed earlier or stay in bed longer to catch up. However, according to Silentnight’s sleep expert, Kathryn Pinkham, this can backfire.
“Many people understandably start going to bed earlier or staying in bed longer to try to ‘catch up’ on sleep, but over time this can weaken the brain’s association between bed and sleep,” Pinkham explains.
To break this cycle and reset your body clock, insomnia experts use a method called sleep restriction. Right this way, please!
What is sleep restriction?
“Sleep restriction, sometimes referred to as sleep compression, is one of the core components of Cognitive Behavioural Therapy for Insomnia (CBT-I), the gold-standard treatment for persistent sleep problems,” says Pinkham. “Despite the name, it is not about depriving someone of sleep.
“It’s about helping rebuild a stronger, healthier relationship between bed and sleep by reducing the time spent in bed to encourage a stronger ‘appetite’ for sleep.”
By limiting your time in bed to closely match the hours you can actually sleep, you create a mild, temporary sleep deprivation. This builds a powerful biological pressure to fall asleep quickly, drastically improving your sleep quality rather than just quantity.
How to calculate your sleep window
To figure out your own specific calculation, you first need to establish your “sleep efficiency” — the percentage of time you are actually asleep versus the total time you spend in bed. Make sense?
The formula is simple:
(Total Sleep Time divided by Total Time in Bed) x 100 = Sleep Efficiency %
For example, if you spend 8 hours in bed but only sleep for 6 hours, your calculation is: 6 hours / 8 hours x 100 = 75% sleep efficiency
The remaining 25% is how much you will want to reduce your sleep window by. Instead of spending 8 hours in bed to get 6 hours of sleep, your new, restricted window would be exactly 6 hours (for instance, 12:00 AM to 6:00 AM).
“The calculation is usually based on a person’s average total sleep time, rather than how long they are spending in bed,” Pinkham notes. “For example, if someone is in bed for eight and a half hours but only sleeping for six, we may initially set a shorter sleep window closer to that six-hour mark, before gradually increasing it as sleep becomes more stable and efficient. This is always adjusted carefully on an individual basis and should never be less than five hours.”
Moving forward, the goal is to gradually improve your sleep. “As sleep drive becomes stronger, sleep often becomes deeper, more consolidated and more restorative. The goal is not less sleep long term, but better-quality sleep and less time spent awake and frustrated in bed.”
How long does it take your body to adjust?
Thankfully, this isn't a permanent lifestyle change. It is a short-term, highly effective intervention designed to fix a specific problem.
“Typically, sleep restriction is used for several weeks as part of a structured CBT-I approach,” Pinkham advises. “Consistency is important, and some people notice improvements within a few days.
“The process should feel gradual and supportive rather than punishing, and it works best when combined with other elements of the programme designed to reduce anxiety and hyper-vigilance around sleep.” Basically, you also need to break that cycle of panicking that you cannot or will not be able to sleep, which ironically makes the ability to actually sleep so much harder.
What if I'm already a good sleeper?
Firstly, lucky you! And secondly, while you may not need to restrict your schedule, you can likely still benefit from the core philosophy of sleep restriction. “For people who already sleep relatively well, strict sleep restriction is usually unnecessary,” Pinkham concludes. "However, some of the principles behind it, particularly maintaining a consistent wake-up time and avoiding spending excessive time awake in bed, can still help improve sleep quality and daytime energy.”
Jennifer Savin is Cosmopolitan UK's multiple award-winning Features Editor, who was crowned Digital Journalist of the Year for her work tackling the issues most important to young women. She regularly covers breaking news, cultural trends, health, the royals and more, using her esteemed connections to access the best experts along the way. She's grilled everyone from high-profile politicians to A-list celebrities, and has sensitively interviewed hundreds of people about their real life stories. In addition to this, Jennifer is widely known for her own undercover investigations and campaign work, which includes successfully petitioning the government for change around topics like abortion rights and image-based sexual abuse. Jennifer is also a published author, documentary consultant (helping to create BBC’s Deepfake Porn: Could You Be Next?) and a patron for Y.E.S. (a youth services charity). Alongside Cosmopolitan, Jennifer has written for The Times, Women’s Health, ELLE and numerous other publications, appeared on podcasts, and spoken on (and hosted) panels for the Women of the World Festival, the University of Manchester and more. In her spare time, Jennifer is a big fan of lipstick, leopard print and over-ordering at dinner. Follow Jennifer on Instagram, X or LinkedIn.
