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In recent years, more and more patients have been presenting to their physician with a feeling of constant fatigue and malaise. Fatigue is a common, nonspecific symptom with a wide range of causes, including acute and chronic medical disorders, psychological conditions, drug toxicity, or substance use.

DEFINITION

The term “fatigue” can be used to describe difficulty or inability to initiate activity (subjective fatigue), decreased ability to maintain activity (fatigue), or difficulty concentrating, remembering, and emotional stability (mental fatigue), individually or in combination. Some patients with the term “fatigue” actually refer to an uncontrollable need to sleep.

Acute fatigue is defined as fatigue lasting less than a month, subacute fatigue is defined as fatigue lasting 1-6 months, and chronic fatigue is defined as fatigue lasting >6 months.

EPIDEMIOLOGY

Fatigue is described as a very significant problem by 21 to 33% of patients visiting primary care settings, with approximately seven million visits per year in the U.S.

CAUSES

Acute fatigue: Acute fatigue is most often attributed to a recent stressor or an acute medical condition, which can often be diagnosed based on its other clinical manifestations. For example, a patient with influenza will describe fatigue in conjunction with fever and respiratory symptoms. Patients with acute fatigue associated with an identifiable medical or psychosocial condition require little or no evaluation.

Subacute and chronic fatigue: Causes include:

• Cardiopulmonary diseases, such as heart failure, chronic obstructive pulmonary disease, sleep apnea.
• Endocrinological/Metabolic diseases, such as hypo/hyperthyroidism, chronic kidney or liver disease, electrolyte disorders (e.g. hypokalemia).
• Hematological diseases (e.g. anemia)
• Neoplastic diseases.
• Infectious diseases, such as Covid-19 disease, infectious mononucleosis, viral hepatitis, HIV infection, tuberculosis.
• Rheumatological conditions such as fibromyalgia, polymyalgia rheumatica, systemic lupus erythematosus lupus.
• Psychological conditions. Depression, anxiety disorder, etc.
• Neurological conditions. Multiple sclerosis
• Side effect of a medication (e.g. benzodiazepines, antidepressants) or substance use (e.g. alcohol, cannabis, cocaine).

The clear cause of chronic fatigue can be identified in approximately 2/3 of patients. In many cases, the feeling of malaise can simply be explained by overwork (long hours of work, few hours of sleep). In a very small percentage, chronic fatigue can be explained by chronic fatigue syndrome (CFS), a disorder of unknown cause but with strong evidence of neurological dysfunction and clear diagnostic criteria. Finally, those who do not meet the criteria for CFS and there is no other explanation for their fatigue are said to suffer from idiopathic chronic fatigue.

MANAGEMENT OF THE PATIENT WITH CHRONIC FATIGUE

The initial assessment of the patient presenting with subacute or chronic fatigue includes obtaining a complete medical history, clinical examination, and basic laboratory tests (complete blood count, electrolytes, renal function, liver biochemistry, TKE, TSH, CPK, CRP). Further diagnostic evaluation is determined by the presence or absence of findings.

Patients with a diagnosed cause of chronic fatigue based on the initial evaluation by an experienced physician should be treated specifically for the condition. For idiopathic fatigue, the use of antidepressant medications, cognitive behavioral therapy, and/or graded therapeutic exercise has been suggested.