World Health Day: Why is Sleep Important for Health?

7th April 2023 marks the 75th anniversary of the creation of the World Health Organisation (WHO). WHO exists to promote health and wellbeing for everyone, everywhere. This year’s theme is ‘Health for All’.

When I think about ways to prevent ill health, and promote recovery, sleep is the single most powerful tool I can think of which is accessible to everyone.

Sleep is the process through which we not only restore our energy levels, but also consolidate memories, remove toxins, repair damaged cells, fight infection, reduce stress levels and regulate our metabolism. Without sleep, we also become more impulsive and less able to make decisions that will positively impact health and wellbeing.

What is healthy sleep?

Healthy sleep patterns can be described in terms of duration, quality and consistency.

How long do we need to sleep for?

Adults of working age are recommended to get between 7 and 9 hours sleep each night for optimal health and daytime function (Hirchkowitz 2015). Above the age of 65, this recommendation narrows to 7-8 hours sleep per night. This recommendation is based on preventing new diseases, as well as managing existing conditions.

For example, a recent study in British adults asked 7,000 adults about sleep at age 50, 60 and 70. Over a 25 year period, people who reported getting five hours of sleep or less at age 50 were 20% more likely to have been diagnosed with a chronic disease and 40% more likely to be diagnosed with two or more chronic diseases, compared to people who slept for up to seven hours ( Sabia 2022). There was no clear risk for sleeping >9 hours in healthy people, but if a participant had already been diagnosed with a chronic condition, then long sleep duration was associated with a 35% increased risk of developing another illness.

What is good quality sleep?

Many people worry that if they wake up during the night, they may have a sleep problem. In fact, we sleep in cycles of lighter and deeper sleep. It is very common to wake up briefly between sleep cycles, especially as we get older. The best indicator of sleep quality is how you feel during the day. Do you wake up feeling well rested? Can you stay alert throughout the day without relying on caffeine, sugar or a nap? Do you feel able to manage your emotions without outbursts of irritation or waves of worry?

When poor sleep quality is persistent, it may meet the criteria for insomnia disorder, which is defined as a dissatisfaction with sleep (falling asleep, waking up during the night, or waking feeling unrefreshed) for 3 nights a week or more, for 3 months or more, which has a negative impact on daytime function (such as work, relationships or mental health). Insomnia often affects people living with chronic conditions, but left untreated, has also been linked to increased risks of future high blood pressure, weight gain, heart disease and mental health disorders ( Perlis 2022).

Why is the consistency of sleep timing important?

Sleep is valuable not only for the time we spend asleep, but also as a critical part of regulating our internal body clocks, or circadian rhythms. Our bodies have evolved to operate on a 24 hour cycle of action during daylight hours and recovery at night. When we maintain regular sleep-wake cycles, all our internal systems work most efficiently, whereas haphazard rhythms put more strain on the body. For example, a recent review found that disruption to circadian rhythms from night work or irregular sleep timing could increase the risks of obesity, high blood pressure, inflammation and diabetes ( Chaput 2023).

So, too little sleep, poor quality sleep and irregular sleep timing can all be linked to a risk of ill health. However, positively, this could mean that improving sleep could reduce the future risk of ill health. Next, we’ll look at some recent studies linking sleep with some of the most common health concerns in the UK.

1. Sleep and Pain

Back and neck pain top the list of causes of morbidity in England - in other words, pain is the most commonly reported cause of ill health. Pain is not a single condition, and doesn’t have a single cause, but it can be related to both mental and physical health. Acute pain and swelling is often caused by an injury or infection, but chronic pain sometimes has no clear cause. The British Pain Society notes that emotions have a powerful effect on pain; “if we feel angry, depressed or anxious, our pain will be worse.”

Pain is a frequent cause of sleep disturbance, and around two thirds of chronic pain sufferers report insomnia. It is less well known that lack of sleep can also increase our sensitivity to pain ( Haack 2020). This can lead to a vicious cycle where a bad night’s sleep enhances pain, which in term disturbs sleep, and further amplifies pain. Scientists are still exploring why lack of sleep promotes pain, but there are likely to be multiple mechanisms including opioid signalling, immune function, melatonin, the stress system and others.

The recommended treatment for insomnia is a talking therapy approach called Cognitive Behavioural Therapy for Insomnia (CBT for Insomnia). Positively, a recent review found that CBT for insomnia is an effective treatment to improve sleep in people with chronic pain ( Whale 2022).

2. Sleep, dementia and Alzheimer’s disease

In 2022, dementia and Alzheimer’s disease were the leading causes of death in the UK. It is known that deep sleep has a cleansing effect on the brain; research shows that short term sleep loss leads to the accumulation of toxins such as beta amyloid and tau which are thought to contribute to the risk of cognitive decline ( Cordone 2019). Sleep disruption is also often a symptom of Alzheimer’s disease. It has been proposed that improving sleep quality, especially deep sleep, in middle age might have protective effects on longer term cognitive function, but as yet, no studies have examined this association.

3. Sleep and Cardiovascular Disease

Cardiovascular diseases, including heart disease and stroke, are among the most common causes of death in the UK. There is a detailed article about the relationship between sleep and heart disease here. A recent review revealed that it is not only insomnia which commonly affects patients after a stroke or transient ischaemic attack (TIA); more than a third will also report sleep apnoea (sleep disordered breathing) or periodic leg movements ( Hasan 2021). Both of these problems can seriously disrupt sleep quality, leading the researchers to recommend early screening and treatment for sleep disorders after a stroke.

4. Sleep and Mental Health

Sleep and mental health are very tightly linked, in a bidirectional relationship. In other words, poor sleep can negatively impact on mental health, while stress and common mental health disorders can negatively impact on sleep (read more here).

Insomnia sufferers are thought to be at more than 3 times the risk of developing future anxiety or depression versus good sleepers, and are also more vulnerable to psychosis, schizophrenia and post traumatic stress disorder (PTSD). Positively, the bidirectional relationship means that when insomnia is successfully treated, patients also often see a significant improvement in their mental health. For example, a review across 65 different trials found that improving sleep led to significant improvements in depression, anxiety, rumination, stress and psychosis ( Scott 2021).

5. Sleep and Infection

Respiratory infections, including covid and influenza, are common causes of both morbidity and mortality. The immune system actively recognises and combats infection during sleep.

In a previous post we noted that sufficient good quality sleep can reduce your risk of viral infection, and potentially improve the effectiveness of a vaccine. It has been suggested that circadian disruption, such as night shift work, increased the risk of severe covid infection ( Rodrigues da Silva 2020 ).

How can you promote healthy sleep patterns?

As we’ve seen above, consistently getting 7 or more hours of good quality sleep is linked to better health outcomes. Whether you are feeling fit and well, or feeling run down, the same simple habits can help to improve your sleep, and improve your health and wellbeing:

●Getting out of bed at the same time, as often as possible - including at weekends. This will help to keep your circadian rhythms in sync.

●Being physically active. The government recommends 150 minutes of moderate or 75 minutes of vigorous physical activity per week, plus 2 strength building sessions, and 2 balance sessions for good health.

●Seeking out natural light during daylight hours. Take breaks outside whenever possible, and work by a window if you can. Two hours before bed, turn down bright overhead lights, and keep your bedroom as dark as possible.

●Finish your main meal at least two hours before you get ready for bed. Eating late can disrupt the quality of your sleep.

●Protect the last 30 minutes of the day to wind down and switch off. Keep your phone and screens outside the bedroom. Use your bed for sleep and intimacy, and nothing else.

What can I do if I’m worried about my sleep?

If you are struggling to cope with a sleep problem, speak to a medical professional for advice. Your GP may be able to give you advice about healthy sleep habits, or rule out other conditions which could be affecting your sleep. The recommended treatment for insomnia is a talking therapy approach called Cognitive Behavioural Therapy for Insomnia (CBT for Insomnia), which can be delivered in person, online, or via a self-help book. Sometimes sleeping pills are also prescribed to help with an acute sleep problem.