Also known as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) or systemic exertion intolerance disease (SEID)
Scott J. Zashin, MD, is board-certified in internal medicine and rheumatology. He was a volunteer clinical professor of internal medicine at the University of Texas Southwestern Medical School Dallas.
Chronic fatigue syndrome is a condition that generally involves deep fatigue, unrefreshing sleep, exercise intolerance, and neurological issues referred to as “brain fog.” At the same time, every person with chronic fatigue syndrome has a unique set of symptoms, the intensity of which can vary.
The exact cause of chronic fatigue syndrome is unknown, but it is believed that a combination of genetic predisposition and environmental factors bring it about. With no simple test to identify it currently available, diagnosis is based on symptoms and the exclusion of other causes. Treatment is aimed at making lifestyle changes that help alleviate the condition and relieving symptoms with medications and therapies.
Symptoms of chronic fatigue syndrome often vary. According to the National Academy of Medicine, fatigue, post-exertional malaise, and sleep problems must all be present in order to diagnose the condition. In addition, a patient must be experiencing either cognitive impairment (brain fog) or a worsening of symptoms while upright (orthostatic intolerance).
Many primary care doctors will be able to diagnose chronic fatigue syndrome. They may also refer you to a doctor who is knowledgeable about or specializes in fatigue disorders, or you may choose to seek out such a practitioner yourself. Physicians who specialize in treating Lyme disease and other autoimmune disorders may also have experience treating patients with chronic fatigue syndrome.
While the causes of chronic fatigue syndrome are still unclear, the condition has been linked to a number of factors, including genetics; viral or other infections; hormone, immune, or central nervous system dysregulation; stress; and exposure to toxins. Some researchers believe the condition may result from several of these factors coming together under the right conditions.
By definition, chronic fatigue syndrome persists for months or years. Recovering from it often hinges on eliminating possible causes, as well as discovering a treatment protocol tailored to your individual body, symptoms, and triggers.
Brain fog is characterized by mental confusion and fatigue. It may feel as if your brain is working more slowly than usual, and you may have slowed reaction times. You may also experience problems with short-term memory, visual perception, or tuning out distractions. Also known as “fibro fog,” these neurological symptoms are common in fibromyalgia and chronic fatigue syndrome.
Many people with chronic fatigue syndrome (CFS) fit the criteria for fibromyalgia syndrome, and vice versa. There is ongoing confusion as to whether these are different conditions or variations of the same disorder. The difference is that CFS has a primary symptom of fatigue, while fibromyalgia has a primary symptom of pain.
The hypothalamic-pituitary-adrenal axis controls your response to stress, regulates sleep, and is involved in mood disorders such as depression. Some research suggests that disruption or dysregulation of the sympathetic nervous system and the hormones involved in the HPA axis may be involved in chronic fatigue syndrome.
Post-exertional malaise causes a spike in symptoms of chronic fatigue syndrome and an energy crash after what, to others, may seem like minor exertion. Many people report that pacing activity according to energy level—perhaps alternating activity with naps or other types of rest—is helpful for managing this common symptom of chronic fatigue syndrome and fibromyalgia.
Centers for Disease Control and Prevention. Myalgic encephalomyelitis/chronic fatigue syndrome. Updated September 18, 2020.
Centers for Disease Control and Prevention. Myalgic encephalomyelitis/chronic fatigue syndrome: IOM 2015 diagnostic criteria. Updated November 19, 2019.
Natelson BH. Myalgic encephalomyelitis/chronic fatigue syndrome and fibromyalgia: definitions, similarities, and differences. Clin Ther. 2019;41(4):612-618. doi:10.1016/j.clinthera.2018.12.016
Tomas C, Newton J, Watson S. A review of hypothalamic-pituitary-adrenal axis function in chronic fatigue syndrome. ISRN Neurosci. 2013;2013:784520. doi:10.1155/2013/784520
McGregor NR, Armstrong CW, Lewis DP, Gooley PR. Post-exertional malaise is associated with hypermetabolism, hypoacetylation and purine metabolism deregulation in ME/CFS cases. Diagnostics (Basel). 2019;9(3):70. Published 2019 Jul 4. doi:10.3390/diagnostics9030070
Goudsmit EM, Nijs J, Jason LA, Wallman KE. Pacing as a strategy to improve energy management in myalgic encephalomyelitis/chronic fatigue syndrome: A consensus document. Disabil Rehabil. 2012;34(13):1140-7. doi:10.3109/09638288.2011.635746
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