The Underlying Causes of Chronic Fatigue
Clarissa Barnes, MD, Board Eligible in Internal Medicine at Yankton Medical Clinic, P.C.
Fatigue, or “a nearly constant state of weariness that develops over time and diminishes your energy and mental capacity,” is a state with which most people can identify (1). Nearly everyone has had this feeling at some point. Usually, fatigue is temporarily and has a clear trigger, such as recent viral illness. Sometimes though, fatigue can become chronic and the causes less obvious. This is a significant problem in the U.S. and accounts for about 7 million office visits per year (2).
The list of possibilities is quite long. And, in many cases, there is no clear answer. Generally, however, the causes of fatigue can be broken up into several categories. The fatigue is usually pharmacologic, psychologic, endocrine/metabolic, infectious, cardiopulmonary, rheumatic, neoplastic/hematologic, idiopathic, or related to sleep disturbances.
Pharmacologic causes are due to either prescription or non-prescription drugs or substances. The most common prescription medications to blame are hypnotics, antidepressants, and antihypertensives (blood pressure). Both drug abuse and withdrawal from illegal drugs can also give people significant fatigue.
Psychologic causes are usually due to depression or anxiety. In addition to fatigue, people will usually complain of changes to their moods, appetites, and social interactions.
Endocrine/metabolic causes include deficiencies such as B12 deficiency, renal or hepatic failure (problems with the kidneys or liver), or systemic endocrine problems such as hypothyroidism (low thyroid levels) or diabetes. More recently, low testosterone levels have gained a lot of attention in the news as a significant cause of fatigue in men. Many companies promise an easy fix with over-the-counter testosterone replacements. However, these supplements are not regulated by the FDA and potentially cause problems. And, true problems with testosterone should be initially be evaluated by your primary care provider to determine if there is an underlying cause that can be corrected!
Infectious causes are usually the more chronic infections. These include HIV, hepatitis, tuberculosis, parasitic infections, mononucleosis, and endocarditis. Many of the tests for these infections used to be reserved for people with clear symptoms. However, now the U.S. Preventative Services Task Force (USPSTF) recommends that clinicians screen for HIV infection in adolescents and adults aged 15 to 65. More recently, they have also expanded the recommendation for Hepatitis C screening to a one-time screen of all adults born between 1945 and 1965.
Cardiopulmonary causes are due to chronic heart or lung issues such as chronic heart failure or chronic obstructive pulmonary disease (COPD). Rheumatic causes are due to systemic autoimmune disease such as rheumatoid arthritis. Neoplastic/hematologic causes include cancer and anemia (low blood counts).
Disturbed sleep causes include sleep apnea and allergic rhinitis. These disruptions these medical problems cause are not usually enough to cause people to wake up fully at night but cause interruptions in the normal sleep cycle that make it difficult to get adequate and quality sleep.
Idiopathic causes are the most difficult causes because, unlike the prior medical issues, there are no specific diagnostic tests for them. Fibromyalgia and chronic fatigue syndrome are diagnoses of exclusion and often require testing for other conditions first.
The start of a new school year can leave anyone feeling tired. However, sometimes fatigue can be a sign of an unaddressed medical issue. How do you know if you're just over-exerting yourself or if there is something else going on? In general, there are many medical, often correctable, causes of fatigue. Figuring out whether or not you have one of these problems can be as simple as scheduling an appointment with your primary care provider to discuss your symptoms and do a thorough physical exam.
Before your appointment, it may be helpful to ask yourself these questions:
- How long have you felt fatigued? Did it start all of a sudden or was it a gradual start?
- Are you fatigued all the time or does it come and go?
- Does it seem to be getting worse from when you first noticed it? Better? About the same?
- Are there certain things or activities that seem to make the fatigue worse?
- Are there things or activities you can do that make your fatigue better?
- Have you had to change your normal patterns of activities to accommodate the fatigue? In other words, are there certain things you can't do in the way you used to or do at all?
- Have other people (family/friends/coworkers) noticed your fatigue? Have they noticed any change to what you've been able to do?
- Have you had any change in your weight? Night sweats? Other specific symptoms that correlate to your fatigue?
2) National Ambulatory Medical Care Survey: 1989 summary. Vital Health Stat 13. 1992.