In addition, increased fatigue severity correlated with greater physical, cognitive, and psychological impairment, although the strength of this link was largely the same between progressive and non-progressive MS patients.
The study, “Prevalence of fatigue and its association with clinical features in progressive and non-progressive forms of Multiple Sclerosis,” was published in the journal Multiple Sclerosis and Related Disorders.
Fatigue, defined in the study as “a subjective lack of physical and/or mental energy that is perceived by the individual or caregiver to interfere with usual and desired activities,” is often regarded as the most debilitating symptom of MS.
Estimates indicate that between 52 percent and 88 percent of MS patients report fatigue. Differences in study populations, outcome measures, and methods used to identify people with or without fatigue explain the large disparity in the reported prevalence of the condition between studies.
It is unclear how exactly MS causes fatigue, with some evidence suggesting it is a direct consequence of disease-related processes, including inflammation and brain damage. Similarly, there is research showing that fatigue can develop independently of MS, due to depression or disability; however, this research is inconsistent.
Additionally, few studies have considered the relationship between fatigue and sleep quality or cognition symptoms common in MS patients, which have been proposed to contribute to its development.
Although fatigue seems to be more prevalent in progressive forms of MS, few studies have considered its association with clinical features specifically in patients with primary– or secondary-progressive MS.
To try and better understand the link between MS and fatigue, researchers from Glasgow Caledonian University in Scotland analyzed the prevalence of self-reported fatigue among patients with progressive or non-progressive MS, and attempted to evaluate the relationship between fatigue severity and impact and clinical features of the disease.
The team collected data using an online survey that was made accessible via a link distributed to potential participants by national and international MS charities and organizations based in the U.S., U.K., and Australia. Inclusion criteria for participating in the survey was a medical diagnosis of MS and a minimum age of 18 years.
In the survey, which took about 30 to 40 minutes to complete, participants self-reported demographic information (including MS type and disability level). They also completed a series of patient-reported outcome measures related to MS impact, quality of life, depression and anxiety, cognition, and sleep. Fatigue severity was assessed using the Fatigue Severity Scale.
In total, the team analyzed 412 participants, of whom 111 reported having a progressive form of MS, whereas 301 reported having a non-progressive form. Of these patients, 308 provided complete survey responses.
Results showed that fatigue was a prevalent symptom, reported by 68.7% of the participants. A higher proportion of participants with progressive MS (81.1%) reported fatigue, compared with those with non-progressive forms of MS (64.1%), confirming the evidence from previous studies that the condition is more prevalent among patients with progressive forms of the disease.
Researchers also found a link between fatigue and MS clinical features, namely that both fatigue severity and impact were associated with higher levels of disability, poorer quality of life, greater depression and anxiety, and poor cognition and sleep quality.
The link between fatigue severity or impact and clinical features was similar between both progressive and non-progressive MS patients.
“Fatigue was more prevalent amongst participants with progressive MS. In addition, higher fatigue severity and impact were associated with greater physical, cognitive, and psychological impairment, although the strength of association between these outcomes was generally similar regardless of the type of MS,” the researchers concluded.
These findings emphasize the multifactorial nature of fatigue in MS and, according to the team, highlight the importance of designing and evaluating interventions aimed at alleviating fatigue in these patients.