The term fatigue can be used to describe difficulty or inability to initiate activity reduced capacity to maintain activity, or difficulty with concentration, memory, and emotional stability (mental fatigue). People may report one or a combination of these symptoms, and they may occur alone or in conjunction with other complaints.
Fatigue is a very common problem. Acute fatigue (lasting one month or less) is most often related to an acute medical condition, which can be diagnosed on the basis of its other clinical manifestations. For example, a patient with the flu will describe fatigue in association with fever and respiratory symptoms. Acute fatigue may also be the result of a recent life stressor.
Chronic fatigue refers to persistent or recurrent fatigue lasting for over six weeks. A specific cause of chronic fatigue can be identified in approximately two-thirds of patients, ranging from heart and lung disease, hormonal imbalances, autoimmune illness, or mental health problems. These are usually diagnosed in Primary Care after a careful review of the clinical history, physical observations, and relevant investigations.
In a small minority of cases, chronic fatigue is explained by Chronic Fatigue Syndrome (CFS).
CFS, also known as myalgic encephalomyelitis (ME), is an illness of uncertain cause. The condition has long been recognized, and many different names have been used to describe it. While underlying objective findings involving the central and autonomic nervous systems, the immune system, and energy metabolism have been described, these have not yet led to a clear understanding of the mechanisms underlying the disease, or to a reliable diagnostic test.
For a diagnosis of CFS to be made, symptoms should be present for at least 3 months, have substantial intensity, and significantly disturb normal function and quality of life.
In addition to fatigue, other criteria include post-exertional malaise, unrefreshing sleep, and cognitive impairment.
People with CFS commonly wake up exhausted and feeling as if they have not slept at all—no matter how long they have been asleep.
Other common symptoms of CFS include chronic pain, Digestive problems, orthostatic intolerance including cardio and respiratory symptoms.