Fatigue

Key facts and checkpoints

• The commonest cause of tiredness is psychological distress, including anxiety states, depression and somatisation disorder. It peaks in ages 20–40.
• An Australian study showed that fatigue presents at a rate of 1.4 per 100 GP encounters.²
• A survey in four NSW general practices by Hickie et al.³ showed that 25% of adult attendees reported prolonged fatigue. Of these, 70% had psychological distress.
• In Jerrett’s study,⁴ no organic cause was found in 62.3% of patients presenting with lethargy; the constant factors were sleep disturbance and the presence of stress in their lives. Many of them turned out to be suffering from psychological problems or psychiatric illnesses, including depression, anxiety state or bereavement.
• An important cause of daytime tiredness is a sleep disorder such as obstructive sleep apnoea, which results in periodic hypoventilation during sleep. It occurs in 2% of the general population in all age groups and in about 10% of middle-aged men.⁴ Obesity and a history of snoring are pointers to the problem. See CHAPTER 60.
• Underlying disorders that need to be considered as possible causes of prolonged fatigue are endocrine and metabolic disorders, malignancy, chronic infection, autoimmune disorders, primary psychiatric disorders, neuromuscular disorders, anaemia, drugs and cardiovascular disorders.
• Prolonged or chronic tiredness is characterised clinically by disabling tiredness, typically lasting more than 2 weeks, associated with non-restorative sleep, headaches and a range of other musculoskeletal and neuropsychiatric symptoms.³
• Sociodemographic correlates are concurrent psychological distress, female sex, lower socioeconomic status and fewer total years of education.³
• Chronic fatigue syndrome (CFS) is defined as debilitating fatigue, persisting or relapsing over 6 months, associated with a significant reduction in activity levels of at least 50%, and for which no other cause can be found.

Selected Differential Diagnosis of Chronic Fatigue

• Cardiopulmonary: congestive heart failure, chronic obstructive pulmonary disease, peripheral vascular disease, atypical angina
• Disturbed sleep: sleep apnea, gastroesophageal reflux disease, allergic or vasomotor rhinitis
• Endocrine: diabetes mellitus, hypothyroidism, pituitary insufficiency, hypercalcemia, adrenal insufficiency, chronic kidney disease, hepatic failure
• Infectious: endocarditis, tuberculosis, mononucleosis, hepatitis, parasitic disease, human immunodeficiency virus, cytomegalovirus
• Inflammatory: rheumatoid arthritis, systemic lupus erythematosus
• Medication use (e.g., sedative-hypnotics, analgesics, antihypertensives, antidepressants, muscle relaxants, opioids, antibiotics) or substance abuse
• Psychological: depression, anxiety, somatization disorder, dysthymic disorder

. Red flags that raise suspicion of serious underlying disease
Red flags	Examples of potential serious underlying disease
Recent onset of fatigue in a previously well older patient	Malignancy Anaemia Cardiac arrhythmia Renal failure Diabetes mellitus
Unintentional weight loss	Malignancy HIV infection Diabetes mellitus Hyperthyroidism
Abnormal bleeding	Anaemia Gastrointestinal malignancy
Shortness of breath	Anaemia Heart failure Cardiac arrhythmia Chronic obstructive pulmonary disease
Unexplained lymphadenopathy	Malignancy
Fever	Serious infection Hidden abscess HIV infection
Recent onset or progression of cardiovascular, gastroenterological, neurological or rheumatological symptoms	Autoimmune disease (eg. rheumatoid arthritis, systemic lupus erythematosus) Malignancy Arrhythmia Coeliac disease Parkinson’s disease Multiple sclerosis Haemochromatosis