Exploring the Impact of Fatigue in Progressive Multiple Sclerosis: A Mixed-Methods Analysis

Background: Patient-focused literature on fatigue in progressive forms of multiple sclerosis (MS) is sparse. This study aimed to explore progressive MS patients' experiences of fatigue.

Methods: Adult patients in the United States with primary progressive MS (n=21) and secondary progressive MS (n=23), recruited from research panels, completed the following PRO measures: Patient Global Impression of Severity (Fatigue) (PGI-F); Fatigue Scale of Motor and Cognitive Functions (FSMC); Modified Fatigue Impact Scale (MFIS); Patient Health Questionnaire, two-item version (PHQ-2); and Patient Determined Disease Steps (PDDS). Patients subsequently participated in a 45-minute semistructured telephone interview and were asked to describe their MS symptoms and to comment on how MS affected their day-to-day lives. More detailed questions followed on the nature of their fatigue, including symptoms, impacts, frequency, and bothersomeness.

Results: Patients' mean age was 52.5 years, mean time since diagnosis was 14.7 years, and 81.8% were female. 79.5% of patients were unemployed and/or receiving disability benefits. Of all spontaneously reported MS symptoms, fatigue was the most common (n=38, 86.4%), followed by ambulation problems (n=31, 70.5%) and muscle weakness (n=25, 56.8%). Patients used the words "tired," "exhausted," "wiped out," and having "little or no energy" to describe their fatigue. More patients rated fatigue as their "most troubling symptom" (n=17, 38.6%) compared with other MS-related symptoms. Half of patients reported feeling constantly fatigued, and more than 90% reported experiencing fatigue at least daily. The top three most frequently reported negative impacts of fatigue were social functioning, emotional well-being, and cognitive functioning (all >80%). Patients described themselves as "homebodies," as fatigue limited their social interactions with friends and family and impacted the types of activities they could participate in. Patients attributed their inability to think clearly or focus for long periods of time to their fatigue. Patients also reported experiencing depression and anxiety because of their fatigue, which would often have further negative effects on their relationships with friends and family. On the fatigue PRO measures, mean (standard deviation) scores were 75.2 (14.7) on the FSMC and 55.0 (15.2) on the MFIS. Most participants scored in the "high" fatigue category on the FSMC (84.1%) and above the clinically significant fatigue threshold (86.4%). MFIS and FSMC total scores correlated with PGI-F (polyserial correlations r=0.74 and r=0.62, both p<0.01) and PHQ-2 (r=0.56 and r=0.57, both p<0.01), but not with PDDS (r=0.09 and r=0.02, both p>0.05).

Conclusions: Fatigue is a common, troublesome, and disabling symptom which has a profound impact on patients' daily lives, as evidenced by qualitative analyses and high scores on established fatigue measures observed in this sample. These findings provide insights into the burden of fatigue and can inform its measurement in both clinical and research settings. Treatments that improve the symptoms of fatigue or prevent exacerbations are needed for patients with progressive MS.

Keywords: Fatigue; Progressive multiple sclerosis; Qualitative; Quantitative.