ME/CFS is currently diagnosed using the presence or absence of certain key symptoms, alongside the exclusion of other potential illnesses. For example, the NICE criteria state that when a person has 4 key symptoms – debilitating fatigue, post exertional malaise, unrefreshing sleep and cognitive difficulties – ME/CFS should be suspected, and further medical assessments must be carried out, including the exclusion of other conditions.
In addition, while not necessary for a diagnosis of ME/CFS, the NICE guidelines state that clinicians should be aware of other symptoms which, although not exclusive to ME/CFS, are commonly experienced by those with the disease, including extreme physical sensitivity to particular substances or conditions (hypersensitivity) such as light, sound, touch, taste, smell, temperature and particular chemicals.
The exclusionary requirement of the diagnosis for ME/CFS places particular importance on being able to differentiate symptoms of ME/CFS from other illnesses with similar symptom profiles, such as multiple sclerosis (MS). This is especially important for lesser investigated symptoms such as hypersensitivity. A recent study noted this, and aimed to look specifically at hypersensitivity to noise and light in people with ME/CFS and those with MS.
Hypersensitivity to noise and sound can occur separately or together. Those with hypersensitivity to noise may find that everyday sounds seem louder than they should, and this can sometimes be painful. Those with light hypersensitivity may have an uncomfortable or painful response from looking at sources of light such as sunlight, fluorescent light or indoor lighting.
While there are currently no estimates of how many people with ME/CFS have noise hypersensitivity, studies looking at vision-related symptoms in ME/CFS have found that between 48% and 92% of people with ME/CFS have some level of light hypersensitivity, with the exact estimates differing between groups of people whose ME/CFS had been diagnosed using different criteria.
The authors of this study therefore wanted to better understand how many people with ME/CFS and MS have noise and light hypersensitivity. They also set out to look at whether these hypersensitivities lead to difficulties that substantially interfere with how an individual is able to function (functional impairment), and if it is possible for these symptoms to differentiate people with ME/CFS from those with MS.
What did the study do?
The study included 2,042 participants with ME/CFS, and 198 participants with MS from multiple, international datasets. Across the different datasets, ME/CFS was diagnosed using different methods – some were self-reported cases of ME/CFS, some were patients referred to CFS or ME/CFS clinics, some were diagnosed using the Fukuda crtieria for CFS, others the Canadian Consensus Criteria (CCC) for ME/CFS, and some had received a diagnosis of ME/CFS from medical professionals.
For all participants with ME/CFS or MS, the DePaul symptom questionnaire (DSQ) – a tool used to provide clear characterisation of illness in a person with ME/CFS – was used to assess the frequency and severity of 54 different symptoms over the last 6 months.
Frequency options were: none of the time, a little of the time, about half of the time, most of the time, or all of the time.
Severity options were: symptom not present, mild, moderate, severe, or very severe.
An additional questionnaire, the 36-item short-form health survey (SF-36), was used to assess the impact of these symptoms on how well participants were able to function physically and mentally.
No direct clinical measurements of noise and light hypersensitivity were taken, rather self-reported frequency and severity of light and noise sensitivities from the DSQ were used. Participants were considered to have hypersensitivity if the frequency was “about half the time” or more, and severity rated as “moderate” or more.
Hypersensitivity was then grouped into:
- Noise only
- Lights only
Authors then considered whether there were differences between those with ME/CFS and those with MS in relation to hypersensitivity to noise and light, and also in how hypersensitivity related to physical and mental functioning in the SF-36 questionnaire, and also other symptoms recorded in the DSQ.
What did the study find?
Compared with the MS group, significantly more people with ME/CFS had both noise and light hypersensitivity, and significantly fewer had no hypersensitivity to either noise or light. The exact proportions observed in the study are shown in the pie charts below.
In both illnesses, those who reported having noise and light hypersensitivity together were found to have lower levels of physical and mental functioning compared with those who had no hypersensitivity.
What do the findings mean?
- While people with ME/CFS are more likely than people with MS to experience noise and light hypersensitivity together, the presence of these hypersensitivities did not accurately differentiate all people with ME/CFS from those with MS.
- Across both disease groups, people with noise and light hypersensitivity together reported lower overall physical and mental functioning. Therefore, the authors suggest that health professionals could use the presence or absence of hypersensitivity to light and sound as an indicator of overall levels of functioning.
- There was little difference between the levels of functioning reported for those with noise hypersensitivity alone, and those with sound hypersensitivity alone. The authors state that these findings support the idea that light and noise hypersensitivity impact functioning in similar ways; for example, through part of the brain that directs attention towards sensory stimuli called the salience network, somewhere abnormalities have been identified in some people with ME/CFS, previously. However, more research is needed to investigate this further.
This study had several limitations. Firstly, people in the ME/CFS group were diagnosed using different methods, meaning that people with different symptom profiles are included which may not be appropriate. While the DSQ, which is a tool designed specifically to look at symptoms included in major case definitions for ME/CFS, was answered by all participants, two different versions of the questionnaire were used and considered together, which again has limitations. In addition, noise and light hypersensitivity symptoms were reported by the participants themselves, rather than using a direct clinical test. While these self-reported measures are useful, they are very individual; for example, what one person perceives to be mild, another may perceive to be moderate.
Understanding how many people experience hypersensitivity, and how these symptoms impact on daily life in ME/CFS, and other similar conditions is important as it may improve diagnosis, and support the development of more targeted treatments. However, more research is needed using a standard case definition for ME/CFS, and clinically assessed measures of hypersensitivity – both noise and light, but also other types of hypersensitivity common in ME/CFS including smell, temperature and certain chemicals.
- ME/CFS is diagnosed using the presence or absence of certain key symptoms, alongside the exclusion of other potential illnesses.
- This exclusionary requirement of the diagnosis for ME/CFS means that it is particularly important to be able to differentiate between other illnesses with similar symptom profiles, such as multiple sclerosis (MS).
- A recent study aimed to better understand noise and light hypersensitivities in people with ME/CFS and MS, and whether these symptoms can differentiate between the two disease groups.
- Compared with those with MS, more people with ME/CFS had both noise and light hypersensitivity together.
- In both illnesses, those who reported having noise and light hypersensitivity together were found to have lower levels of physical and mental functioning compared with those who had no hypersensitivity.
- While hypersensitivity to noise and light did not accurately differentiate all people with ME/CFS from those with MS, the presence of noise and light hypersensitivity did give a useful indication of overall level of functioning.
- The findings of the study are limited by the methods used to diagnose ME/CFS and the lack of clinical assessment of noise and light hypersensitivity.
- More research is needed using a standard case definition for ME/CFS and clinically assessed measures of hypersensitivity – both noise and light, but also other types of hypersensitivity.