Poor sleep quality in people with ME/CFS has been linked with lower quality of life.
Research into the underlying causes of sleep dysfunction in ME/CFS is limited, but suggests:
- Reduced nocturnal heart rate variability may contribute to unrefreshing sleep.
- Reduced deep sleep (also known as slow-wave sleep activity).
Despite evidence of sleep dysfunction in ME/CFS, research into its underlying causes remains limited. Many studies use the Fukuda criteria for chronic fatigue syndrome (CFS), which do not consider post-exertional malaise (PEM) – the cardinal feature of ME/CFS – as essential for diagnosis. Nevertheless, the studies which have been done provide a foundation for future research.
Researchers also face additional challenges when investigating sleep and ME/CFS, these include:
- Difficulties diagnosing primary sleep disorders, such as sleep apnoea, complicates the isolation of sleep dysfunction due to ME/CFS.
- Participants with severe forms of ME/CFS may be unable to travel to a lab for overnight studies.
- Comorbidities, like orthostatic intolerance, can also impact sleep.
Research challenges
Difficulties diagnosing primary sleep disorders, such as sleep apnoea, complicates the isolation of sleep dysfunction due to ME/CFS.
Primary sleep disorders are challenging to diagnose for several reasons, including the complex diagnostic process, and symptom overlap with other illnesses, including ME/CFS, In fact, both ME/CFS and sleep disorders – such as sleep apnoea – can present with non-restorative sleep, cognitive impairment (“brain fog”), and profound exhaustion. Due to this overlap, it is difficult for researchers to accurately identify whether sleep disturbances are as a result of ME/CFS, or due to an underlying sleep disorder.
Participants with severe forms of ME/CFS may be unable to travel to a lab for overnight studies.
Sleep studies often require participants to attend a ‘sleep lab’, in person, which is likely to be inaccessible for those with more severe forms of the ME/CFS. While monitoring sleep at home is possible, researchers are not yet able to capture the same level of detail that they would be able to in the lab. Additionally, in the lab, the environment (noise, light, temperature) is ‘controlled’, meaning that it is the same for each participant – differences in environment between participants could affect results and influence conclusions drawn.
Comorbidities, like orthostatic intolerance, can also impact sleep.
Many people with ME/CFS have other diseases or medical conditions that are present at the same time, known as comorbidities, such as orthostatic intolerance, and fibromyalgia. These comorbidities may also impact sleep, further complicating the task of any researcher investigating the association between sleep and ME/CFS.
Resources
1. ME Research UK articles relating to sleep dysfunction in ME/CFS
- Sleep reversal and ME/CFS
- World Sleep Day 2025
- Assessing sleep and pain problems in adults with ME/CFS
- Sleep loss can hurt brain
- Sleep Disturbances
2. Completed research funded by ME Research UK relating to sleep:
