In preparing for the annual rite of teaching clinical skills to medical students, I was once again reminded of the importance of obtaining an “accurate history,” performing a proper and thorough physical examination, and obtaining necessary and pertinent laboratory testing. How easy it is to go down the wrong diagnostic path if one has erroneous information and makes the wrong assumptions. One excellent example is the frequent complaint of “weakness” when in fact the person is really complaining of feeling “fatigued.” There are over 10 million visits per year to the primary care provider for problems relating to fatigue, with approximately 50% of the U.S. population reporting being fatigued for at least part of the day. While there is no universally accepted definition, the one I prefer is that fatigue is the sensation of exhaustion during or after normal activities and the lack of sufficient energy to initiate a desired activity. Frequently, patients may use the term fatigue to describe boredom, sleepiness, weakness, dyspnea on exertion, or even a distaste for work.

It is essential to distinguish fatigue from true weakness, a finding that can be confirmed on physical examination and warrants a thorough evaluation for a neurologic or muscular cause of the complaint. If no physical findings can be elicited, a complaint of weakness can be considered to be synonymous with fatigue. Under certain circumstances, any healthy individual may have fatigue, otherwise referred to as physiologic fatigue. This may result from inadequate sleep, overactivity, poor physical conditioning, stress, or even a change in diet. This is more common in persons working evenings or nights, new parents, students, shift workers who have rotating shifts, and healthcare professionals. The elderly who may have chronic problems resulting in anxiety, pain, or disturbed sleep-wake cycles are also vulnerable to this cause of fatigue.

It is important, however, especially in the elderly, to rule out organic causes of fatigue. Fatigue may result from anemia, congestive heart failure, chronic renal failure, metabolic abnormalities, infections, among many other causes, some of which may be treatable and thus allow an improvement in symptoms of fatigue. Malignancy may also result in fatigue, as may a myriad of medications. Psychogenic causes are of particular concern, with over 40% of the elderly having mild or moderate depression and life-changing events that in themselves can lead to anxiety and stress. One large series identified that over 50% of patients complaining of fatigue in fact had psychogenic causes; approximately 40% of cases in this study were due to organic disorders.1 While this high number is not universally accepted as fact, it does reinforce the importance of considering psychogenic causes in anyone complaining of fatigue.

While there are specific clues to help define the etiology of fatigue, such as its relation to time of day, activities, and association with other signs/symptoms of disease, sometimes laboratory testing is required to screen for certain potential causes. Although perhaps all too frequently overdiagnosed, chronic fatigue syndrome should also be considered, even though this problem is not a frequent cause of fatigue in the older person. In order to make the diagnosis of chronic fatigue syndrome, the fatigue should be associated with four or more of the following symptoms that persist or recur during six or more consecutive months of illness, and that do not predate the fatigue: self-reported impairment in short-term memory or concentration; sore throat; tender cervical or axillary nodes; muscle pain; multi-joint pain without redness or swelling; headaches of a new pattern or severity; unrefreshing sleep; and post-exertional malaise lasting more than 24 hours.2

In the end, most agree that no definite diagnosis can be established in up to 30% of persons complaining of fatigue. These individuals need to be followed over time for the development of new signs and symptoms of organic or psychogenic disorders. As with so many other areas of medicine, persons who have a problem without a clear answer are identified as having an “idiopathic” cause of their problem, in this case idiopathic chronic fatigue. There is much more to write on this vast topic; I will stop, however, as I believe I have made my point regarding the need for accurate information—and I too am getting fatigued!

Send comments to Dr. Gambert at medwards@hmpcommunications.com