What is fatigue?

Symptoms of fatigue

Fatigue is described as a severe state of exhaustion that cannot be compensated for by rest and sleep. As such, fatigue is a symptom that can manifest itself in both physical and mental states.

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Physical symptoms of fatigue

Physical symptoms of fatigue are varied and affect multiple systems of the body. Typical signs are

• Chronic fatigue:
  A persistent feeling of tiredness that is not relieved by rest, sleep or holidays. Those affected often feel as if they are ‘burnt out’.
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• Sleep disturbances:
  Although many people with fatigue feel the desire to rest, they often suffer from sleep problems. These include difficulty falling asleep, non-restorative sleep or waking up frequently during the night.
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• Dizziness and headaches:
  Persistent fatigue can lead to dizziness, light-headedness or recurring headaches.
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• Muscle weakness and aching limbs:
  Many sufferers feel physically weak, even after simple tasks such as climbing stairs. Muscle and joint pain without a clear cause can also occur.
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• Impaired physical endurance:
  People with fatigue often have difficulty performing strenuous activities or being physically active for long periods of time. Even light activities can feel extremely exhausting.

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Mental symptoms of fatigue

Mental fatigue is an equally important aspect of fatigue. It can manifest itself in the following symptoms:

• Concentration and memory disorders:
  Those affected often report brain fog. This describes a cognitive impairment in which it is difficult to think clearly, concentrate or retain information. Short-term memory may be impaired and it is difficult to organise tasks.
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• Mood swings and emotional exhaustion:
  Fatigue is often accompanied by depressive moods, irritability or anxiety. Mental exhaustion can significantly impair the ability to cope with stress.
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• Diminished mental stamina:
  Just as with physical stamina, many people with fatigue find it difficult to concentrate on work or perform mental activities for long periods of time. Even reading a short text or holding a conversation can be exhausting.

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Occurrence of fatigue

Fatigue can occur in two ways: as a separate syndrome known as chronic fatigue syndrome (CFS), or as a comorbidity of other chronic diseases such as long Covid, cancer, multiple sclerosis, rheumatoid arthritis or fibromyalgia. Although the symptoms can be similar in both cases, the causes and progression of these fatigue states differ.

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Fatigue as an independent syndrome (chronic fatigue syndrome)

Chronic fatigue syndrome, also known as  Myalgic encephalomyelitis (ME), is a distinct disease characterised by extreme, persistent fatigue that is not improved by physical exertion or rest. The exact mechanism that causes CFS is not yet fully understood. However, researchers suspect that immune disorders, infections or neurological changes may play a role.

Sufferers report profound exhaustion, which - depending on its severity - occurs even after minimal exertion such as brushing their teeth or getting dressed. This exhaustion can last for days or even weeks. Other symptoms include sleep disorders, concentration problems, muscle pain and headaches.

Another characteristic of chronic fatigue syndrome is the so-called post-exertional malaise (PEM) - a worsening of symptoms after physical or mental activity that is disproportionate to the exertion exerted. This typically occurs with a time delay to the overexertion.

Increased sensitivity to light and noise as well as depressive moods or anxiety disorders can also accompany the syndrome.

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Fatigue as a side effect of chronic illnesses

Fatigue also frequently occurs as a concomitant symptom of chronic conditions such as cancer, multiple sclerosis, rheumatoid arthritis or heart disease. In these cases, the fatigue is caused by the underlying illness, but in some cases also by its treatment. In cancer patients, for example, fatigue is often a side effect of chemotherapy or radiotherapy. Fatigue can also play a central role in autoimmune diseases in which the immune system is chronically overactive.

The symptoms of fatigue associated with other illnesses are often similar to those of chronic fatigue syndrome. The exhaustion can manifest itself both physically and mentally. Unlike CFS, however, specific triggers such as pain, inflammation or the treatment itself can often be identified in the case of fatigue as an accompanying illness.

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Diagnostics and therapeutic approaches

The diagnosis of fatigue, especially chronic fatigue syndrome, is often difficult. This is because there are no clear laboratory tests or imaging procedures. It is usually made by taking a thorough medical history and ruling out other illnesses.

Therapeutically, there is still no specific cure for fatigue. Depending on the cause and severity of the fatigue, various approaches are pursued. These can include symptomatic treatment, physical therapy, psychological support and lifestyle adjustments. In some cases, adapted exercise therapies are also used.

Regardless of the cause and severity, Pacing is recommended as a measure for the conscious use of available energy resources.

Psychological approaches such as cognitive behavioural therapy can also help, especially if fatigue is accompanied by anxiety or depression.