When you get a great night’s sleep, you wake up refreshed and rejuvenated. What goes on behind the scenes as you drift off to dreamland remains a mystery, but we do know that many different kinds of changes take place during sleep.

For example, it is clear that brain activity is different when you are asleep than when you are awake. It is also known that muscles relax and body systems such as the digestive and endocrine systems are active. Those changes during sleep have a profound impact on health. In fact, in June 2022, the American Heart Association added sleep to its list of modifiable factors that can help reduce cardiovascular disease risk, alongside diet, exercise, smoking status, blood pressure, cholesterol and sugar levels, and weight.

It is not clear, however, why we need sleep. One theory suggests that it developed during evolution as a protective mechanism against predators at night. Another is that it is essential for the operation of many of the body’s metabolic processes, including those that keep you healthy and strong.

In addition, it is well established that lack of sleep can lead to a wide variety of medical problems such as obesity, mental illness and heart disease. In many cases, sleep disorders may be related to some form of stress or anxiety.

Scientists have not yet fully understood what is happening during sleep, but they have identified several important functions that it appears to serve. One is restorative, which means that your brain and body are actively repairing damaged cells and tissues during sleep. It is also important for memory formation, and it seems to play a role in learning and creativity.

Another important function of sleep is to support the immune system by helping your body fight off germs and bugs. In fact, it has been shown that getting enough high-quality sleep can improve your ability to resist infection, as well as to recover from illness and make you feel better faster.

The timing of your waking and sleeping patterns is also important. The sleep-wake cycle is regulated by your biological clock, which operates on a daily time scale. This is why you are usually more alert and able to concentrate during the day, while your mood and energy tend to be lower at night.

Maintaining a regular schedule of sleep and waking at the same times each day can help you get the most out of your sleep. It is recommended that you aim for 7-8 hours of high-quality sleep each night. If you are unable to sleep well, talk to your GP for advice. They can help you identify and treat any underlying causes that might be contributing to your insomnia. In some cases, sleep aids such as melatonin and certain medications can be helpful. However, there are also non-medical strategies that can be used to improve sleep, such as relaxation training.