Chronic Fatigue Syndrome
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- A condition characterized by (1) profound mental and physical exhaustion, (2) with at least 6 months presence of multiple systemic and neuropsychiatric symptoms, and (3) at least 4 of 8 associated conditions are required per CDC definition:
- Impaired memory
- Sore throat
- Tender lymph nodes
- Persistent muscle or joint pain
- New headaches
- Nonrefreshing sleep
- Postexertional malaise
- Must have a new or definite onset (not lifelong). Fatigue is not relieved by rest and results in >50% reduction in previous activities (occupational, educational, social, and personal). Other potential medical causes must be ruled out.
- Patients are excluded from chronic fatigue syndrome (CFS) definition until 2 years after resolution of substance/alcohol abuse, 5 years after resolution of anorexia nervosa or bulimia, and if they have BMI ≥45.
- Predominant age: 20–50 years
- Predominant sex: Male < Female
- All socioeconomic groups
- Various, and at times contradictory, associations between ethnicity and incidence have been reported. Higher rates found in ethnic minorities (Native Americans and African Americans) compared with white populations, based on a population study. Service-based studies (tertiary care) have reported higher rates among whites, or no association between incidence and ethnicity (1).
Estimates vary widely and depend on case definition and population studied, but a reasonable estimate using a strict case definition is 100 cases per 100,000 population. Community-based studies have reported prevalence rates of 0.23% and 0.42%.
- Personality characteristics (neuroticism and introversion)
- Childhood inactivity or overactivity
- Inactivity in adulthood after infectious mononucleosis
- Familial predisposition
- Comorbid mood disorders of depression and anxiety
- Long-standing medical conditions in childhood
- Childhood trauma (emotional, physical, sexual abuse)
- Prolonged idiopathic chronic fatigue (4)
Higher concordance among monozygotic twins compared with dizygotic twins
- Unknown and likely multifactorial:
- Possible interaction between genetic predisposition, environmental factors, an initiating stressor, and perpetuating factors
- Physiologic or environmental stressor could be precipitant.
- Many patients with chronic fatigue recall significant stressors (e.g., major medical procedure, loss of a loved one, loss of employment) in months before symptoms began.
- Systems hypothesized to contribute to physiology include:
- Neuroendocrine (e.g., diminished cortisol response to increased corticotropin concentrations)
- Immune (e.g., increased C-reactive protein and beta-2 microglobulin) (5)
- Neuromuscular (e.g., dysfunction of oxidative metabolism) (5)
- Autonomic (orthostatic hypotension is reported in a proportion of CFS sufferers)
- Serotonergic (e.g., hyperserotonergic mechanisms or upregulation of serotonin receptors)
Commonly Associated Conditions
Common comorbidities include:
- Fibromyalgia (more common in women)
- Irritable bowel syndrome
- Temporomandibular joint disorder
- Anxiety disorders
- Major depression
- Posttraumatic stress disorder (including physical and/or sexual past abuse)
- Domestic violence