Amber Salter, PhD

Amber Salter, PhD,
Section Head, Statistical Planning & Analysis,
Associate Professor, Biostatistics,
UT Southwestern

Most individuals with MS reported mild fatigue early in their disease course, at least one-half of whom experienced increasing fatigue over time, according to findings presented at the 2022 Consortium of Multiple Sclerosis Centers annual meeting.

“Fatigue is commonly reported in persons with [MS] and is associated with poor quality of life and reduced social participation and performance of daily activities,” Amber Salter, PhD, and colleagues wrote. “However, most studies examining fatigue are limited to smaller sample sizes or short follow-up.”

Dr. Salter and colleagues examined the natural history of fatigue using data from the North American Research Committee on MS Registry. Participants had 7 years or less of longitudinal data between 2004 and 2019 and a relapsing disease course at the time of enrollment, with 5 years or less since their MS diagnosis. Dr. Salter and colleagues evaluated fatigue with the Fatigue Performance Scale (FPS), a single-item measure with 6 responses—normal (0) to total (5)—and defined fatigue worsening as at least a 1-point increase in the FPS score at the next survey. FPS score at the first survey update served as the index fatigue level. They also measured disability with the Patient-Determined Disease Steps (PDDS) scale.

Increases in Fatigue Tied to Disability Progression

Among 3,057 patients with longitudinal data available, 30.9% (N=944) were within 5 years of an MS diagnosis and had relapsing MS. Most participants were women (83.5%) and White (87.5%). The mean age at enrollment was 44.5 (42.6 at diagnosis), and the median PDDS scale score was 2, indicating moderate disability.

At baseline, the following fatigue levels were reported: normal (9.4%), minimal (17.8%), mild (23.8%), moderate (24.4%), severe (20.6%), and total (4.0%). While the mean age at index and at diagnosis increased in conjunction with fatigue levels (both P<0.001), age at symptom onset was comparable across FPS scores. Participants with a higher fatigue level at index were more likely to report relapse in the 6 months before index.

With the exception of those with severe fatigue, most participants indicated worsening fatigue at each FPS level: no (69.7%), minimal (71.4%), mild (60.9%), moderate (57.4%), and severe (20.6%). Time to fatigue worsening ranged from 3.2-5.4 years across each level of fatigue, and a significantly greater number of individuals with minimal or mild index fatigue and fatigue worsening reported PDDS scale progression compared with no worsening (minimal: 73.3% vs 47.9%; mild: 75.2% vs 51.1%; P<0.01).

“Because participants with worsened fatigue also report disability progression, such associations should be examined further,” Dr. Salter and colleagues wrote.