Is chronic fatigue syndrome just being very tired?

Chronic fatigue syndrome, or myalgic encephalomyelitis, is when an individual experiences profound fatigue for at least six months.

This fatigue must also not be lifelong to rule out our genetic metabolism or neuromuscular issues.

It must also not be due to ongoing excessive exertion.

However, many people may experience long-lasting fatigue, a symptom of many conditions.

So, what differentiates chronic fatigue syndrome as a diagnosis from chronic fatigue as a symptom?

One key symptom which is pathognomonic to chronic fatigue syndrome and ME is post-exertional malaise.

Post-exertional malaise is a worsening of the individual symptoms after exerting themselves.

These symptoms include increased fatigue, but notably, they also include symptoms that would not be expected to occur after physical or cognitive exertions.

These include sleep, memory, concentration and mood issues and influenza-like feelings such as a sore throat.

There may also be the development of new symptoms which the individual did not have before the exertion.

The symptoms are also disproportionate to the initiating event.

Therefore, the type and severity of symptoms is one key factor.

Another factor is that the initial trigger does not just have to be physical.

It can also be cognitive, orthostatic, emotional, or sensory.

These factors increase stress on the body, leading to worsening symptoms.

The combination of the variety of triggers as well as the unusual symptoms gives post-exertional malaise its distinguishing features.

These features help differentiate an individual with the symptom of chronic fatigue from those with the diagnostic condition of chronic fatigue syndrome.

The post-exertional malaise is so specific to chronic fatigue syndrome and ME that the new preferred term for the condition is systemic exertional intolerance disease.

Along with the profound fatigue and post-exertional malaise, the diagnosis also requires sleep disturbances and either cognitive impairment or orthostatic intolerance.

Combined, these symptoms form a particular clinical entity that is not simply about how fatigued or tired an individual is.

The intolerance to exertions and the symptoms that occur after it are at the heart of the diagnosis.