Tired all the time? Here’s a formula for the perfect night’s sleep

“I tumble out of bed and stumble to the kitchen,

Pour myself a cup of ambition,

Yawn and stretch and try to come to life.”

If Dolly Parton’s famous lyrics describe your morning routine after yet another night of broken sleep, then you’re in good company.

Multiple research projects have shown people around the world are not getting enough sleep. That in turn prompts an important question: how many hours should we sleep each night?

Scientists from the UK and China went in search of the answer to that question, studying data on the sleep patterns, health and overall wellbeing of half a million people. The participants are members of the UK Biobank, a long-term health study backed by the UK Government.

It’s well known that a lack of sleep can reduce our ability to concentrate, so, before you nod off, the conclusion of the study is that we should be getting 7 hours of solid sleep every night. That figure applies to people aged 38 to 73. As we move from birth, through adulthood to old age, the number of hours we need to sleep changes.

The findings are broadly in line with research from the American Sleep Association which mapped the ideal night’s sleep across our lifespans.

Researchers working on the UK/Chinese study found seven hours of sleep was associated with a longer attention span, better memory and the ability to learn new things. People who slept well were also better equipped to solve problems and make effective decisions.

They also found that people who enjoyed an ideal night’s sleep had better mental health and suffered fewer symptoms of anxiety, depression and overall poor wellbeing. Conversely, extreme lack of sleep, getting just 4 or 5 hours a night is associated with increased mortality.

It may seem logical to assume that if seven hours constitutes a great night’s sleep, eight or nine hours might be a way of supercharging your cognitive abilities and mental health. But scientists warn that the reverse is true and that having too much sleep can lead to poor health outcomes, particularly in regard to cognitive function.

For example, excessive sleep has been associated with an increased risk of dementia. The researchers also found that optimal sleep patterns have a beneficial effect on brain structure in older people.

In people who slept well, the researchers found that parts of the brain contained more grey matter and a larger volume of cortical material.

"While we can't say conclusively that too little or too much sleep causes cognitive problems, our analysis looking at individuals over a longer period of time appears to support this idea," Jianfeng Feng, a professor at China's Fudan University and an author of the study, said.

With so many health benefits associated with a good night’s rest, what can we do when sleep proves elusive or we struggle to wake up in the morning? The American Sleep Association recommends creating a “sleep hygiene” routine, a pattern of behaviours that promote sound sleep, including:

Go to bed at the same time, wake up at the same time.

Taking naps reduces the hours of sleep we need at night and builds up sleep debt.

The blue light from digital devices can disrupt circadian rhythms that promote sleep.

Caffeine can prevent and fragment sleep. If you drink caffeine, do so only before noon.

Open a window slightly if you can to circulate air in the bedroom.