The sleep we get affects almost every tissue and system in the body. Getting too little sleep over time raises your risk for chronic diseases, including high blood pressure and cardiovascular disease. In addition, poor quality sleep can damage your memory, make it difficult to concentrate and learn, and affect how well you react and interact with others.
In order to stay healthy, most adults need about seven to nine hours of sleep each night. However, work schedules, day-to-day stressors, a disruptive bedroom environment, and medical conditions can prevent us from getting enough restful sleep. Insufficient sleep can also be the first sign of a sleep disorder.
Scientists are still learning about the complex processes that occur during sleep, but we know that it involves a number of vital functions. Major restorative processes such as tissue growth and repair, muscle growth and protein synthesis, and immune function all happen during sleep. These activities are important for maintaining and improving physical health, but they are also critical to our mental health and quality of life.
When you are sick or have an overly busy day, your body’s desire for sleep increases. This is called sleep drive. The sleep you get in those circumstances is usually longer than normal, as your body tries to catch up on the rest it needs. Similarly, sleeping longer during vacation or after exercise is a normal response to the need for recovery.
Sleep drives and the need for rest are part of a regulatory system, which is controlled by the circadian clock and other bodily rhythms that operate on a daily time scale. These rhythms also control our hunger, thirst, body temperature, and metabolic rate.
Several theories are offered for why we need sleep, but one of the most plausible is that, through evolution, nighttime sleep developed as a natural protective mechanism against predators who were more active at night. The inactivity theory suggests that nighttime sleep allowed prey to avoid being attacked by predators until morning, when it was safe to leave their hiding places.
A growing body of evidence shows that, when we don’t get enough sleep, it can have a profound impact on our mental and physical functioning, as well as our mood, emotions, and ability to respond to stress. Research also indicates that sleep deprivation can contribute to a wide variety of health problems, such as high blood pressure, heart disease, diabetes, obesity, and depression.
It’s important to remember that the results of many studies examining sleep and health are self-reported, which means they may be biased by personal beliefs or experiences. This can lead to false conclusions and inaccurate comparisons between groups. Furthermore, most large-scale studies of self-reported sleep patterns have failed to take into account a number of factors that can influence reported sleep duration and quality (e.g., work schedules, family and social relationships, illness), or fail to assess underlying factors that can cause sleep disturbance, such as obstructive sleep apnea or insomnia.