Fatigue

Fatigue describes a state of tiredness (which is not sleepiness) or exhaustion. In general usage, fatigue often follows prolonged physical or mental activity. When fatigue occurs independently of physical or mental exertion, or does not resolve after rest or sleep, it may have other causes, such as a medical condition. Fatigue (in a medical context) is complex and its cause is often unknown. Fatigue is associated with a wide variety of conditions including autoimmune disease, organ failure, chronic pain conditions, mood disorders, heart disease, infectious diseases and post-infectious disease states. Fatigue (in the general usage sense of normal tiredness) can include both physical and mental fatigue. Physical fatigue results from muscle fatigue brought about by intense physical activity. Mental fatigue results from prolonged periods of cognitive activity which impairs cognitive ability. Mental fatigue can manifest as sleepiness, lethargy, or directed attention fatigue. Mental fatigue can also impair physical performance. Fatigue in a medical context is used to cover experiences of low energy that are not caused by normal life. Fatigue is multi-faceted and broadly defined, which makes understanding the cause of its manifestations especially difficult in conditions with diverse pathology including autoimmune diseases. The use of the term "fatigue" in medical contexts may carry inaccurate connotations from the general usage of the word. More accurate terminology may also be needed to cover variants within the umbrella term of fatigue. Fatigue is generally considered a more long-term condition than sleepiness (somnolence). Although sleepiness can be a symptom of a medical condition, it usually results from lack of restful sleep, or a lack of stimulation. Fatigue is often described as an uncomfortable tiredness, whereas sleepiness can be comfortable and inviting. Central nervous system fatigue Muscle fatigue Fatigue can have significant negative impacts on quality of life.