Network Analysis of Symptoms Co-Occurrence in Chronic Fatigue Syndrome, 2021, Kujawski, Staines,Newton et al

Abstract
Chronic fatigue syndrome (CFS) is a heterogenous disorder of multiple disabling symptoms with complex manifestations. Network analysis is a statistical and interrogative methodology to investigate the prevalence of symptoms (nodes) and their inter-dependent (inter-nodal) relationships. In the present study, we explored the co-occurrence of symptoms in a cohort of Polish CFS patients using network analysis.

A total of 110 patients with CFS were examined (75 females). The mean age of the total sample was 37.93 (8.5) years old while the mean duration of symptoms in years was 4.4 (4). Post-exertional malaise (PEM) was present in 75.45% of patients, unrefreshing sleep was noted in 89.09% and impaired memory or concentration was observed in 87.27% of patients. The least prevalent symptom was tender cervical or axillary lymph nodes, noted in 34.55% of the total sample.

Three of the most densely connected nodes were the total number of symptoms, sore throat and PEM. PEM was positively related with impairment in memory or concentration. Both PEM and impairment in memory or concentration presence are related to more severe fatigue measured by CFQ and FIS. PEM presence was positively related with the presence of multi-joint pain and negatively with tender lymph nodes and muscle pain. Sore throat was related with objective and subjective autonomic nervous system impairment.

This study helps define symptom presentation of CFS with the pathophysiology of specific systems and links with multidisciplinary contemporary molecular pathology, including comparative MRI.

https://www.mdpi.com/1660-4601/18/20/10736

 

Although an interesting starting point, surely this sort of study needs large sample sizes to produce meaningful results.

Acceptable definitions of ME/CFS are essential for meaningful results and at our current stage of knowledge comparing the results from people diagnosed under different criteria would be of interest, especially as the study reports only some 75% of their subjects experienced PEM, which many would argue they did not have the supposed condition being studied.

Also I would want to know how they drew up their symptom list and whether they included co-existing conditions, as at our current state of knowledge we can not unambiguously assert which are co existing conditions and which are symptoms, for example I get migraines triggered by food intolerances, migraines with no obvious trigger and migraines that are associated with PEM, so are migraines a co existing condition or an ME symptom.

Ultimately producing a symptom list is a ‘boot strap’ operations, starting with asking patients open ended questions that allow them freedom to include any response, then producing a list, but going back to asking whether this list allows people to cover all their symptoms or if it misses anything out. There also needs consideration of how fine a detail of symptom definitions is required, for example is it relevant to just identify cognitive issues or do you need to distinguish sensory issues from language issues from memory issues from ordering complex activities, or even do you need to distinguish within such as language issues. It would probably require more focused separate research to establish what level of detail within individual symptom categories, eg cognition or orthostatic issues, produced consistent or useful results.

Obviously have not read the full article yet but also you would want to know if the symptoms reported were present currently, in the last few months, or even in the whole course of the illness, which only appeared along with or subsequent to onset, and which had occurred in some for prior to onset, for example I occasionally experience migraines prior to the onset of my ME, but now regard them as a symptom of my ME, as successfully managing my ME (and diet) helps minimise their occurrence, in contrast I have only ever been aware of orthostatic intolerance post onset.

Also do symptoms relate to variation in the ME, for example some symptoms only appear in an ongoing relapse or in conjunction with PEM, eg for me Costocondritis, but others such as orthostatic intolerance though worse during PEM are relatively constant and others such as my food intolerances that a developed post onset of my ME depend on what I eat rather than my current severity or any PEM, despite themselves worsening my other ME symptoms.

Further are their any relationships between symptom patterns and the type of onset, gender, overall current severity of ME, age, time since onset, how stable over time are individuals patterns of symptoms, etc?

Also how would people with other conditions respond to these symptom lists, what are the differences between ME and idiopathic chronic fatigue, between ME and such as MS, etc.

Though repeating this is an interesting study, it is only baby steps in the whole process of developing a description or natural history of ME, but even if they only come up with a usable symptom list that is a start.

 

Looks like this paper simply reports some correlations between symptoms and other questionnaires.

The Chalder Fatigue Scale (CFQ) and PEM had a correlation of 0.26, which isn't that high.

 

That seems very strange to me. Tender lymph nodes and muscle pains were core symptoms of ME and are a big part of PEM for many of us. Multi joint pain is a constant for me not just during a crash.

It may all come down to definitions and how the questions are framed.