• Sleep apnea is a common disorder that can cause daytime fatigue without the patient being aware of the problem. Apnea is actually a breathing disorder that is often marked by loud snoring and thrashing in bed. A person may not realize the problem exists unless it is brought to his or her attention by a sleeping partner or observer.
• Narcolepsy is a peculiar and rare disorder in which a person suddenly falls asleep without any previous signs of fatigue.
• Other sleep disorders that cause daytime fatigue include insomnia and restless legs syndrome (RLS).

Researchers have found that people with CFS have altered amounts of slow wave sleep, which could indicate a problem with sleep regulation. Non-restorative sleep and nighttime restlessness are the most common complaints of people with CFS.

Conditions that Cause Joint Pain, Muscle Aches, or Both. A number of illnesses cause one or more CFS symptoms, including arthritic symptoms, fever, and fatigue.

Severe Obesity. People who are severely obese often have symptoms of chronic fatigue because of the stress imposed by their weight. People who are obese are also at higher risk for sleep apnea, which can confuse the diagnosis.

Other Medical Conditions that Usually Rule Out CFS. Many diseases, both minor and serious, can cause prolonged or chronic fatigue, including:

• Anemia
• Anorexia nervosa or bulimia nervosa
• Chronic kidney disease
• Diabetes
• Hemochromatosis (a hereditary disease caused by iron overload)
• Hepatitis
• Hypothyroidism
• Neuromuscular diseases (such as myasthenia gravis)
• Various forms of cancer

Drugs and Alcohol. Fatigue is a side effect of many prescription and over-the-counter medications, such as antihistamines. In addition, dependency on or abuse of alcohol or illicit drugs may lead to chronic fatigue. Medications should be considered as a possible cause of fatigue if an individual has recently started, stopped, or changed medicines. Withdrawal from caffeine can produce depression, fatigue, and headache.

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Review Date: 01/10/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)