Don’t delay your bedtime for this important sleep reason, says doctor

Do you struggle to fall asleep at night? Or maybe you can’t resist staying up to watch one more episode of your favourite TV show. But while you might think it’s not a big deal to delay your bedtime, you could actually be missing out on a very crucial phase of sleep.

For viral sleep hacks, many people are turning to TikTok where doctors like NHS surgeon Dr Karan Raj create content that offers medical advice, sleep tips and debunks health myths. In a recent video from Dr Raj, he explains that by delaying your bedtime, you won’t just feel tired the next day but you could be affecting your hormone production and general health and wellbeing.

The phase Dr Raj is referring to is slow wave sleep. But what is it and why does it matter? Keep reading to find out.

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What is slow wave sleep?

Slow wave sleep (SWS) or deep sleep is a period of non-rapid eye movement (NREM) sleep which is characterised by high-amplitude low-frequency waves. This stage of sleep typically happens during the first few hours of sleep and lasts between 70-90 minutes. In Dr Raj’s video, he explains that “the early part of the night is dominated by NREM sleep. This is important because NREM sleep includes the deeper restorative slow wave sleep that’s coupled with the biggest release of growth hormone in your 24 hours.”

The growth hormone (which is produced by the pituitary gland located at the base of the brain) is what fuels childhood growth and maintains your body’s organs and tissues throughout your life, according to Mayo Clinic. Around 70% of this hormone comes from the slow wave sleep stage which is why it’s so important to make sure you’re not delaying your bedtime.

But why? Dr Raj explains that “as the night goes on, the ratio of NREM to REM sleep changes and you get progressively less NREM and more REM sleep. If you cut short your bedtime, you cut the short time you spend in slow wave sleep and so you get less of that growth hormone.”

And that’s not all – it turns out that as we get older, we start to get less slow wave sleep. “Into your 30s and 40s, the total amount of growth hormone release in 24 hours decreases as does the amount of slow wave sleep.” What this means is that by wasting time scrolling on your phone or staying up for an hour or more longer than you normally do, you’re reducing or cancelling out entirely the amount of growth hormone your brain releases and your body receives.

This hormone is particularly important for children and teenagers to continue growing but as you get older, a lack of this growth hormone is not only a sign of aging but it can affect your body fat, aerobic capacity, and muscle and brain mass. As stated in his video, Dr Raj says that this is why it’s important to go to bed at a similar time every day, so you get every bit of that growth hormone.

In general, having a set bedtime routine is a sign of good sleep hygiene, so you should be aiming to do this anyway, to ensure you have the best night’s sleep and wake up the next day feeling refreshed and motivated.