Slow wave sleep - it’s one of the most important sleep stages and can help with everything from memory to sharpness. However, it dwindles with age. Here’s how to get more

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Sleep - we could all do with more of the stuff. Especially of the slow wave variety, the deep sleep state that is particularly beneficial for boosting our mental and physical health - it’s what keeps us sharp and makes us wake up more rested plus, it can help reduce the risk of developing diseases such as dementia and Alzheimer’s.

“Slow wave sleep is often referred to as the foundation of youth,” psychologist and sleep expert Hope Bastine  tells me. “During deep sleep, the slow delta brainwave state, the body temperature, blood pressure and heart rate are at their lowest, allowing the body to carry out essential maintenance, healing and boosting of the immune system that wards off vulnerability to illness.”

Accounting for around 25 per cent of our shut-eye each night, it’s been shown to help with everything from learning to memory. Unfortunately though, this incredibly useful type of sleep dwindles with age. For women, the decline starts at around 35 and for men, around 55. So, incorporating ways to up our levels as we approach middle age can prove to be an effective way to lessen the impact on our bodies and brains.

Slow wave sleep occurs in stages three and four of the five stage sleep process, following light sleep but preceding the REM dream stage. Our muscles are extremely relaxed and it’s especially hard to wake up. However, as Hope points out, our calm exterior belies the hamster wheel of activity going on beneath the surface. “Even though we may appear motionless in deep sleep, our brain is doing its best work,” she says.

Aside from the physical benefits, it’s the monumental effect slow wave sleep has on our mental wellbeing that’s most interesting, in particular, its pivotal role in memory processing. Essentially what it does is help the brain sort out the dealings of the day and lays down the groundwork for better mental recall.

It also acts as a ‘mental detox’ of sorts to reduce the risk of developing neurological diseases. Hope tells me that during slow wave sleep, our brain is bathed with nutrient-rich synovial fluid which clears out clutter such as amyloid beta (which is associated with age-related memory disorders such as dementia and Alzheimer’s). In short, it helps sift through the crap. “During our seven to nine hours of recommended sleep, our brain is being flushed of the daily residue of toxin build-up each time we cycle through all five sleep stages,” explains Hope. “Interestingly, we need five cycles to flush out all the toxins. Think of it like a washing machine cleaning your laundry with a number of spin cycles.”

How do you know if you’re not getting enough?

“In the short-term, you’ll know immediately if you have not had enough deep sleep,” says Hope. The number of hours that you’ve slept for isn’t a clear indicator. “You will wake up, even though you may have still had the seven to nine hours you usually need, still feeling tired, sluggish, fatigued, irritable, have difficulty concentrating , focusing, or remembering, and may later see a decreased level of collagen in the skin. Most notably, you will feel heavy headed, like having the flu, which may be because of the toxins not being effectively flushed out of your brain.”

Long-term, the signs are memory problems, a decrease in problem-solving or big picture thinking and slower wound recovery.

How can you get more of it?

Ah, the million dollar question. The reasons for disturbed sleep are vast and while there’s no suits-all solution, here are some ideas that can help - and the findings that back them up.

1. Drink less

Booze and brews (of the caffeinated kind) don’t have the best of relationships with your bed due to their effect on both your deep sleep and REM cycles. “Alcohol and caffeine destroy the K fibre and sleep spindle formation necessary for deep slow wave sleep,” Hope explains. It doesn’t mean that you need to go teetotal, but rather, look to recalibrate your timings.

For alcohol, Hope recommends drinking mindfully  by sticking to one unit per hour (as this is how long it takes for your liver to process alcohol) and flushing it out with plenty of water. For caffeine, get your fix early in the day. “The effects of caffeine stay in the body between 12 to 14 hours,” she tells me. “50 per cent of us metabolise it quickly whereas 50 per cent of us don’t. If you fall within the latter category, make sure you time your morning coffee/tea right to allow for the caffeine to be well out of your system by the time you wish to be asleep. Also try experimenting with what the optimal amount for you should be. If you are an anxious insomniac, you really should be avoiding caffeine altogether.”

2. Make some pre-sleep routine swaps

I’m a creature of habit, and in the past, many of the night time rituals that I thought helped me to sleep, were actually having the opposite effect (prime examples include dozing off in front of the TV or mindlessly scrolling through Instagram). If this sounds familiar, Hope recommends starting a pre-sleep routine around 60 to 90 minutes before you hit the hay to help get your body relaxed and your mind in a calm, alpha pre-slumber state to support a smooth cycle through the sleep stages. Activities should focus on helping you disengage from analytical thinking. “They are usually creative like: listening to calming music or playing an instrument, meditation , contemplating artwork or doing art, reading poetry and literature (but not psychological thrillers), writing in a journal (with pen and paper), and listening to audiobooks/bedtime stories,” she says.

MORE GLOSS: The rise of the grown-up bedtime story

3. Listen to pink noise

Found by US experts to improve slow wave sleep and boost memory, you can tap into this ear-friendly frequency courtesy of a number of apps. “Listening to pink noise either during a pre-sleep meditation for at least 20 minutes or even throughout the night, especially if you are living in a noisy urban area, can help,” says Hope. “The pink noise can be masked nicely with sounds of water or being in nature. The app, Sonic Sleep , plays the delta sound wave at a barely audible level but your sleeping brain recognises and synchronises with it.”

Another app, a free download called Pink Noise , operates in a similar way and sounds like a waterfall or power shower with a distant jingling in the background. To get the most out of it, pop in your headphones and place your device face down, or connect to a Bluetooth speaker instead if you want a bit more ear space.

4. Try a slow wave sleep-prompting gadget

Tech is developing in such a way that it’s fast becoming a valuable ally rather than an enemy of a restful night’s sleep. A point proven by Zeez , whose Alpha Device and Sleep Pebble work to slow the brain down and make your shut-eye that much more restorative. “Using technological devices that enhance deep sleep like the Zeez can help,” says Hope. “They use electromagnetic stimulation to help your brain cycle through the sleep stages naturally, including the maximum amount of delta slow wave sleep.”

5. Banish blue light

That being said though, invoking a time limit on other handheld gadgets can help keep your relationship with tech healthy. “Research shows that the blue light emitted from devices issues a one hour phased delay of melatonin, the sleep hormone necessary for sleepiness and effective cycles through the sleep architecture stages,” explains Hope. Her advice? Banish blue light 60 to 90 minutes before you plan to go to bed to ensure that you don’t lose out on valuable snooze time.

Read more: Night time anxiety - what to do when you can’t sleep.

Follow Hope  @FPWellbeing  and Ayesha  @Ayesha_Muttu .