Sleep is vital to everyday functioning, and consistently poor sleep quality can significantly affect even healthy individuals. For people with ME/CFS — who already contend with a wide array of debilitating symptoms — sleep disturbances can be particularly challenging. In fact, sleep difficulties are a common and frustrating feature of ME/CFS, with individuals reporting a wide range of sleep disturbances, including sleeping too much or too little, fragmented sleep, difficulty falling asleep, and sleeping at inappropriate times.
Sleep reversal study
A team of researchers at DePaul University (USA) recently investigated a specific sleep disturbance: sleep reversal (also known as sleep inversion), where individuals are awake at night and sleep during the day. It is estimated that sleep reversal affects 10% of people with ME/CFS reporting sleep difficulties. The study aimed to compare symptoms and functional impairment in individuals with ME/CFS with and without sleep reversal.
With a dataset of 2313 individuals with ME/CFS (327 with sleep reversal, 1986 without sleep reversal) aggregated from six countries, the researchers had access to demographic data and responses to the following questionnaires:
- DePaul Symptom Questionnaire (DSQ) – Previously developed by one of the researchers in the study, Leonard Jason, this self-report tool assesses ME/CFS symptoms such as fatigue, post-exertional malaise (PEM), sleep disruption, pain, cognitive impairments, and autonomic, neuroendocrine, and immune issues.
- Medical Outcomes Study Short-Form Health Survey (SF-36) – Evaluates health across eight domains: physical functioning; role limitations due to physical health; bodily pain; general health; vitality; role limitations due to emotional problems; social functioning; and mental health.
Key findings
The study found that individuals with sleep reversal were “more impaired” than those without it across nearly all DSQ domains and all SF-36 domains. The authors concluded the study “provides evidence that sleep reversal identifies a more impaired subgroup within the population of individuals with ME/CFS.”
Predictors of sleep reversal
- Strongest Predictor: Difficulty falling asleep – unsurprising given that “if a person has sleep reversal, by definition difficulty falling asleep would be indicated”.
- Second Strongest Predictor: Younger age – possibly due to higher inflammation levels in younger individuals, as according to the researchers: inflammation tends to decline over the course of ME/CFS. Although, the researchers also speculated that greater use of technology and irregular light exposure in younger participants might contribute.
- Other Predictors: Higher BMI, loss of appetite, nausea, and twitching (such as in restless legs syndrome), and four pain features (muscle pain, joint pain, soreness and SF-36 pain subscale). The researchers mention that pain is strongly associated with inflammation, which links back to the correlation between sleep reversal and inflammation.
SF-36 emotional wellbeing scores were notably lower in the sleep reversal group. The study points out that even in the general population, poor sleep is linked to increased depression and anxiety. Given the severity of sleep dysfunction in sleep reversal, greater emotional impairment in this group is understandable.
Study limitations
The researchers acknowledged several limitations:
- Potential varying interpretations of sleep reversal by participants
- Limited diversity in the sample (predominantly white females), affecting generalisability
- Exclusion of potential influencing factors such as medication usage
Conclusion
This study points to those with sleep reversal being a more impaired subgroup of individuals with ME/CFS. The researchers highlight predictors of sleep reversal, such as younger age, and suggest that inflammation may be a major underlying cause of this particular sleep disturbance.
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