see also stress; chronic fatigue syndrome; psychiatry and mental health; Coping with shift work; sleep hygiene, insomnia

• fatigue can be defined as a pervasive sense of tiredness or lack of energy that is not related exclusively to exertion.
• fatigue, like pain, is intrinsically a brain-mediated sensation, although, as with pain, people report that fatigue is experienced as a peripheral phenomenon, apparently occurring in musculoskeletal regions. Most patients also experience “mental fatigue”, typically precipitated by complex neuropsychological tasks.
• it is a common complaint in the community & is usually transitory, and 10-25% of patients presenting to GPs have prolonged and disabling fatigue, 5-15% have chronic fatigue whilst 0.5-2.5% have chronic fatigue syndrome (CFS)
• after infectious mononucleosis, reporting of prominent fatigue: 41% during acute illness; 71% at 1 month; 43% at 2 months; 9% at 6 months;
• fatigue must be differentiated from:
  • muscle weakness (eg. myopathy, polymyositis)
  • neuromuscular fatigability (eg. myasthenia gravis)
  • central fatigue of physical & mental fatigue at rest (eg. multiple sclerosis)
  • anhedonia - lack of motivation to commence tasks & lack of pleasure from tasks undertaken (eg. major depression)
  • somnolence - daytime sleepiness, short sleep latency (eg. sleep apnoea, narcolepsy)
  • breathlessness (eg. COPD, cardiac failure, anaemia)
  • inflammation/infection causing muscle/joint pain, fever, malaise (eg. SLE, influenza, fibromyalgia)
  • anxiety - panic attacks, avoidant behaviour

• the following list is not exhaustive:
• physiological:
  • sedentary lifestyle & lack of exercise
  • sleep deprivation
• diet:
  • fluctuations in blood sugar, resulting from the consumption of refined carbohydrates, lead to spikes and crashes in energy, manifesting as mid-afternoon slumps and persistent tiredness.
  • lack of essential nutrients, like iron, magnesium, and B vitamins, can compound this effect
• poor sleep hygiene
• persistent stressors:
  • workplace-related:
    • shift work
    • career “burn-out” - see coping strategies for ED staff
    • change-induced
  • personal-related:
    • marital disharmony
    • financial stress - unemployment, high debt levels, gambling
    • complex, excessively demanding lifestyle
    • always on digital connectivity
  • social-related:
    • social isolation and loneliness adversely impacts mental health and resilience against fatigue
• drugs:
  • medications - beta blockers
  • alcohol & drug dependence
• infectious diseases:
  • HIV/AIDS, chronic hep. B/C
  • post EBV / glandular fever / infectious mononucleosis
• autoimmune disorders:
  • systemic lupus erythematosus (SLE), rheumatoid arthritis, Sjogren's syndrome
• endocrine disorders:
  • hypothyroidism, diabetes mellitus
• cardiorespiratory disorders:
  • chronic airflow limitation, cardiac failure
• GIT disorders:
  • coeliac disease, inflammatory bowel disease
• haematological disorders:
  • anaemia
• sleep disorders:
  • obstructive sleep apnoea
• neuromuscular disorders:
  • myasthenia gravis, multiple sclerosis (MS)
• metabolic disorders:
  • hypercalcaemia
• psychiatric & psychological disorders:
  • major depression, anxiety disorder, somatisation disorder, school phobia
• occult malignancy
• occupational & environmental factors:
  • organic solvents, heavy metals
• chronic fatigue syndrome

• unexplained fatigue < 1 month duration:
  • routine evaluation of acute medical & psychological disorders (eg. acute EBV, bereavement)
  • R/V in 1 month
• prolonged fatigue > 1 month duration:
  • detailed evaluation of medical & psychological disorders:
    • hypothyroidism
    • anaemia
    • major depression
  • R/V monthly
• at 3 months:
  • comprehensive fatigue assessment:
    • medical Hx & exam
    • psych. Hx & exam
    • FBE, ESR, U&E, Ca, PO4, LFTs, TSH, urinalysis for protein, blood, sugar
    • Ix as indicated by clinical evaluation
    • BUT the following are not currently routinely recommended:
      • serology for EBV, enteroviruses, Lyme disease in Australia
      • tests of immunity
      • urinary protein metabolite screening
      • neuroimaging studies
      • autoantibody assays
      • CK
  • R/V monthly
• at 6 months:
  • chronic fatigue syndrome diagnosis & Mx:
    • make specific Dx of CFS
    • provide information about CFS
    • consider contact with support groups
    • enlist social welfare agencies
  • R/V monthly
• at 12 months:
  • comprehensive fatigue assessment
  • annual review