Fatigue

Fatigue is a condition in which a person's physical or mental capacity for work declines following sustained activity, or as a result of illness. It differs from simple sleep deprivation; a fatigued person may feel exhaustion even while resting.

Fatigue can be divided into two main types: physical fatigue, which involves a decline in the ability of muscles to produce force, and mental fatigue, which involves a decline in concentration, memory, and decision-making. Both types often occur together, especially during prolonged work with irregular hours.

Physical mechanisms

When muscles are used for extended periods, changes occur in the cells and nerves that supply the muscle. These include depletion of energy stores (glycogen), accumulation of metabolic byproducts, and a decline in the efficiency with which calcium moves muscle contraction. There is also a component originating from the brain that reduces the signals sent to the muscles (central fatigue).

Health-related causes

Persistent fatigue is a widespread symptom associated with many disorders: anemia, thyroid dysfunction, heart disease, infections, conditions of the heart and liver, and mental health conditions such as depression and anxiety. Certain medications and sleep disorders, such as sleep apnea, can also cause fatigue.

Fatigue and occupational safety

Fatigue is an important factor in vehicle and workplace safety. Pilots, drivers, healthcare workers, and those working night shifts face elevated risk of error. Working hours are regulated, rest periods are scheduled, and fatigue risk management systems are employed.

Investigation and management

Investigation begins with the patient's history, assessment of sleep, and laboratory tests to identify physical causes. Management is based on treating the underlying cause where one is found; when no clear cause is identified, treatment consists of graded exercise, sleep hygiene, and psychological support.