Fatigue Prevalence Remains High in MS Patients
The prevalence of fatigue continues to be high among people with multiple sclerosis (MS) despite significant progress over the years in therapies that change the course of the disease, a large survey study in Norway found.
The findings also show that the frequency of fatigue is higher in women and associated with anxiety, depression, and daytime sleepiness.
Although there is no universally accepted definition, fatigue is commonly described as a loss of physical and/or mental energy. In people with MS, fatigue is a major factor that affects quality of life. Yet, there still are no effective treatments that specifically target this symptom.
Previous reports suggested that fatigue in MS has a prevalence of 50–90%. However, large population-based studies have not been carried out in the past 20 years to confirm these numbers. The researchers also suggested that, with recent changes in diagnostic criteria and the emergence of new disease-modifying therapies (DMTs), the prevalence of fatigue actually could be lower.
“Our hypothesis was that the prevalence of fatigue in patients with MS is lower than previously reported due to changes in diagnostic criteria, possibly resulting in the detection of more benign cases, and the introduction of more efficient disease modifying drugs,” the researchers wrote.
To test their hypothesis, the team analyzed data from patients with MS in three Norwegian counties — Buskerud, Oslo, and Telemark (collectively, BOT). The BOT registry has information on 3,965 patients diagnosed with MS at the Vestre Viken Hospital Trust, Telemark Hospital Trust, and Oslo University Hospital.
“All the patients in the registry who were alive and residing within the three counties as of 2017, were invited to participate in the study,” the researchers wrote.
In total, 2,512 patients were asked to complete a questionnaire that included three tests: the Fatigue Scale for Motor and Cognitive Functions (FSMC), the Epworth Sleepiness Scale (ESS), and the Hospital Anxiety and Depression Scale (HADS).
The response rate was 64% — 1,599 of 2,512 people who received the questionnaires. Of the 1,599 patients who returned the written consent form and questionnaires, 1,454 answered 17 or more of the 20 questions on the FSMC. These patients were considered participants in the study; non-participants included all those who were not invited, did not respond to the questionnaire, or who failed to respond completely.
The majority of participants in the study were women (70%), their mean age was 52, and their median disease duration was 16 years. Almost half (48%) of participants had received their MS diagnosis more than 10 years before the survey. Relapsing-remitting MS accounted for 83% of the patients, followed by progressive MS (9%).
The majority of MS patients (1,182 of 1,454, or 81%) reported experiencing fatigue. Within this group, 15% had mild fatigue, 19% had moderate fatigue, and 67% reported severe fatigue. A total of 1,119 participants (77%) had cognitive fatigue, and 1,188 (82%) had motor fatigue. While those younger than 40 reported equal levels of mental and physical fatigue, older patients experienced more physical fatigue than mental fatigue.
More women than men reported fatigue (83% versus 78%), even when researchers adjusted the results for age, disability level, and the presence of depression/anxiety.
Fatigue increased with age and was significantly higher in patients aged 50 or more than those younger (86% versus 75%). However, this association was no longer evident after considering sex, disability level, and anxiety/depression.
Patients with fatigue also had greater disability than patients without fatigue (EDSS score of 3.0 versus 2.0 in those without fatigue. (The higher the EDSS score, the greater a person’s disability level.)
A larger number of patients with progressive MS reported fatigue compared to those with relapsing-remitting MS (88% versus 80%), but no link was established when researchers adjusted the data for age and MS severity.
Anxiety was more frequent in patients with fatigue than in those without (20% versus 3.3%). Similarly, depression (11% versus 0%) and daytime sleepiness (42% versus 11%) also were more prevalent in patients with fatigue.
“There is a large degree of symptom overlap between these conditions. Whether fatigue precedes depression and anxiety, or the causality is the other way around, remains to be determined,” the researchers wrote.
The team determined that although age, sex, subtype of MS, and disease severity all were associated with fatigue, based on multivariate analysis (analysis of complex data with multiple variables) only sex, disease severity (disability level), and anxiety/depression were independent factors.
Overall, contrary to what was expected, “we found that the prevalence of fatigue is high in contemporary patients with MS despite the advances that have been made in diagnostics and treatments over the past 20 years,” the researchers concluded.
The team noted that more research is needed to investigate the complicated relationship between DMTs use and fatigue.