Expert shares five bedtime mistakes that ruin your night's sleep

Positive effects of a good night sleep stretch into every aspect of our lives. We feel energetic, focused, ready to take on the day. Long-term effects of bad sleep are less known. But they have a huge impact on our health and even how long we live.

Alzheimer's, obesity, cancer and diabetes are all linked to poor sleep. So, what's the latest science on how we can improve our sleep, and by extension, our overall health?

Speaking on the ZOE Science & Nutrition podcast, Prof. Matthew Walker, a Liverpool-born professor of neuroscience and psychology at UC Berkeley, has shared some tips for a deep, undisturbed night's sleep.

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1. Alcohol

A common misconception is that alcohol helps us slip into a deep sleep. However, Prof. Walker warned alcohol is "anything but a sleep aid". While alcohol is labelled as a sedative, sedation is not sleep.

Prof. Walker said: "A night cap doesn't make you fall asleep any faster, but you lose consciousness more quickly. Alcohol fragments your sleep. You wake up many more times throughout the night, but the problem is you don't remember waking up. The next morning, you feel unrefreshed, but you can't remember waking up, so you don't put two and two together."

2. Bright lights

Lighting plays a huge part in how quickly we fall asleep. Sitting in a brightly lit room before bedtime disrupts the production of melatonin, which our brains produce as it gets darker to ready us for sleep.

Prof. Walker said: "We are a dark deprived society in our modern era and we need darkness at night to trigger the release of a sleep hormone called melatonin. As a tip, try doing the following experiment: in the last hour before your [bedtime] set an alarm on your phone.

In that last hour, dim down half of the lights in all of your house and you will be surprised at how sleepy that increased darkness will make you feel, and what that tells you is normally you are supressing the release of the 'sleepiness' hormone melatonin."

3. Caffeine

Many health benefits of coffee have been established in recent years. Antioxidant properties found in coffee beans can improve gut health, while caffeine improves focus and can even aid in better fat breakdown.

Yet, drinking coffee before you go to bed can cause a disturbed and fragmented sleep, and could even age you by a decade. Prof. Walker said: "drink coffee because the health benefits that have been associated with coffee are profound and very reliable. But when it comes to sleep, the dose and the timing make the poison.

"Try to limit yourself to two cups of coffee, maybe three. The critical thing is cut yourself off at least 12 hours before you expect to go to bed. Caffeine can decrease the amount of deep sleep you have by somewhere between 12 to 15%" depending on the dose of caffeine. To reduce the amount of deep sleep you have by 15% would age you by about 10 to 12 years."

4. Screens

It's common practice for many of us to be scrolling through our phones before we go to sleep. But Prof. Walker says there's nothing worse we can do for our sleep.

He said: "Our screens are enriched in the blue LED light spectrum which is the worst for melatonin levels and suppresses them the most powerfully. These devices are designed to capture your attention, make you alert and keep you awake, sustained and engaged."

To avoid the temptation of using your phone before bed, Walker suggests keeping phones out of bedroom altogether. "If you absolutely have to take your phone in the bedroom, only use it standing up. You might think after about five or six minutes, I'll sit down on the bed. No; at that point, you're done, put the phone away."

5. Temperature

While we may typically associate warmth with comfort and drowsiness, Prof. Walker recommends keeping your bedroom cool at night to help achieve optimum sleep. The ideal temperature, according to Walker, is around 18 to 18.5 degrees Celsius.

He said: "I know it sounds cold but cold it must be. You can keep your feet warm - hot water bottles, socks - but the ambient must be cold." He recommends making your room like a cave - dark and cool - in order to have the best night sleep you can.