Is chronic fatigue syndrome just tiredness? How to recognise it

12 May marks World ME/CFS Day, the international acronym for myalgic encephalomyelitis/chronic fatigue syndrome. The name can be misleading: ‘chronic fatigue’ might suggest persistent tiredness, but this condition is something radically different and far more debilitating, and can significantly reduce the quality of life of those affected. In the World Health Organisation’s International Classification of Diseases (ICD-11), it is included in the chapter on diseases of the nervous system, although its nosological classification is still a matter of debate within the scientific community. For years it was largely overlooked, often dismissed as a problem ‘in the patients’ heads’, but scientific advances are finally changing this situation.

ME/CFS is a complex chronic illness that affects several systems in the body: the nervous system, the immune system and cellular energy metabolism. It can affect people of all ages, but is most common between the ages of 30 and 50 and appears to affect women more frequently than men. It often appears suddenly, following a viral infection, although in some cases the onset is gradual. Although it is a condition recognised by the international scientific community, it has long been underestimated in the past: many patients have reported years of misdiagnosis or delayed diagnosis, and of not being taken seriously. The minimum duration required for a diagnosis is six months of persistent symptoms, which must be carefully assessed by a doctor. Although some national guidelines, such as those of the UK’s National Institute for Health and Care Excellence (NICE), set out precise diagnostic criteria, there is still no unanimous international consensus on how to definitively diagnose this syndrome.

No, and this is one of the most dangerous misconceptions about this illness. The key symptom of ME/CFS – the one that distinguishes it from any other form of fatigue – is called ‘post-exertional malaise’ (PEM). This is a marked worsening of all symptoms that occurs after physical or mental exertion, even very mild exertion such as going for a walk or making a video call, and which can last for hours, days or even weeks. This means that doing ‘more activity’ does not help a person feel better: in fact, it can significantly worsen the patient’s condition. In addition to PEM, people with ME/CFS typically report: intense fatigue that is not relieved by rest (also called ‘fatigue’, to distinguish it from the more common and normal kind of tiredness); difficulty concentrating and with memory, often described as ‘brain fog’; non-restorative sleep (waking up feeling just as tired as before going to sleep, as if one’s ‘battery’ never recharges); muscle and joint pain; symptoms that worsen when standing for long periods, such as dizziness or a rapid heartbeat (orthostatic intolerance).

There is no blood test or MRI scan that can diagnose ME/CFS: the diagnosis is clinical, meaning it is based on a thorough and systematic assessment of symptoms by a doctor, after ruling out other possible causes. The most up-to-date international guidelines, published in 2021 by the UK’s NICE, set out precise diagnostic criteria and recommend that diagnosis be made within a reasonable timeframe to avoid delays in treatment. With regard to treatment, gradual exercise therapy had long been recommended. However, the 2021 NICE guidelines have marked a clear shift in this approach: gradual exercise should not be recommended for people with ME/CFS as it may worsen symptoms, and the same caution applies to certain forms of psychotherapy previously used as treatment. The approach now considered safest is known as pacing, which involves the conscious management of available energy, learning to stay within one’s limits to avoid post-exertional malaise. There are no medicines specifically approved for this condition. Care must be multidisciplinary, with the support of GPs and specialists capable of managing individual symptoms.

Yes, and this is one of the areas on which research is focusing most intensively. Many people who have had Covid-19 continue to experience persistent symptoms for weeks or months after getting over the acute phase of the infection: this condition is known as ‘long Covid’ (we have discussed it in numerous articles). Some of these patients develop a clinical picture very similar to, and in part overlapping with, that of ME/CFS, including post-exertional malaise as a core symptom. Recent studies published in international scientific journals estimate that a significant proportion of people with long Covid meet the diagnostic criteria for ME/CFS. This has led to renewed scientific interest in the condition, with an increase in research funding globally. If, following an infection, you experience severe fatigue, cognitive difficulties and post-exertional malaise that do not improve after a few weeks, it is important to discuss this with your GP, who will be able to assess your overall clinical picture and refer you for appropriate care.