According to MedlinePlus, most adults under age 60 need about eight hours of sleep per night. Feeling occasional tiredness and exhaustion is not usually a problem when the cause is apparent and symptoms are easily remedied by rest and other self-care measures. However, tiredness is largely subjective, a fact which can make it tricky to pinpoint the cause. Lifestyle factors such as activity, stress, diet and sleep habits all influence how tired a person feels at any given time. On the other hand, fatigue is also a symptom of many illnesses, some of which are harmless and transient, while some others are serious. MedlinePlus underscores the importance of seeking medical help whenever sleep, stress reduction and proper nutrition fail to improve symptoms of fatigue.
Exertion
Fatigue caused by exertion is the body's way of signaling that it is time for rest. Competing demands of work, school, family and social responsibilities are often enough to temporarily deplete a person of energy and enthusiasm. Physical, mental and emotional exertion can be extremely tiring if enough care is not taken to also rest and revitalize, even in the absence of underlying medical problems.
Lack of Sleep or Poor Quality Sleep
Sleep disturbances are a major contributing factor of fatigue. Some people suffer from insomnia that is attributed to an underlying medical condition, such as sleep apnea, restless leg syndrome or depression. In other instances, poor quality sleep is the result of not getting the recommended minimum eight hours of sleep per night. Parenting small children is yet another experience that can wreak havoc on getting adequate, uninterrupted sleep. Whenever lack of sleep is to blame for tiredness, the issue needs to be addressed however possible. According to the National Institutes of Health, a lack of sleep can negatively impact memory, attention, cognitive function, motor reflexes and emotional health.
Illness
Tiredness is a common feature of many illnesses. Persistent and intense fatigue unexplained by another cause can be a sign of chronic fatigue syndrome, which can be debilitating. Viruses, infections, cancers, some kinds of anemia, depressive disorders and sleep apnea often manifest with fatigue as a central symptom. Physical and emotional causes of tiredness and fatigue are not always illnesses, however. Normal grieving and pregnancy are only two examples of biological processes that often precipitate feeling tired. It is essential to consult a physician whenever unusual or persistent feelings of tiredness persist.
