Cognitive symptoms, mood disorders vary with MS subtype
Different manifestations suggest need for tailored treatment, study finds
Cognitive symptoms, mood disorders, and fatigue manifest differently in relapsing-remitting and progressive forms of multiple sclerosis (MS), a study found.
“[O]ur results indicate that the subtype of MS is associated with … specific kinds of cognitive deficits, suggesting the need for subtype-specific therapeutic interventions,” the France-based research team wrote. Their data also captured how these symptoms changed after a year, revealing more cognitive improvements in some treated subtypes than others.
The study, “Cognitive impairment, mood, and fatigue in various multiple sclerosis subtypes: a one-year follow-up study,” was published in the Journal of Neurology.
The different subtypes of MS, a chronic neurodegenerative disorder, reflect how MS symptoms develop and progress over time. Relapsing-remitting MS (RRMS) accounts for about 85% of new MS diagnoses, and includes alternating periods of symptoms worsening and easing.
In progressive forms of MS, symptoms gradually worsen over time. Secondary progressive MS (SPMS) is a disease stage that follows RRMS, with up to 40% of people with RRMS converting to SPMS within two decades, despite treatment. Primary progressive MS (PPMS) describes cases in which progression starts at disease onset.
Comparing cognitive symptoms
Regardless of subtype, MS can lead to cognitive impairment, which may include difficulty with learning and memory tasks, physical and mental fatigue, attentional deficits, and emotional problems like depression and anxiety.
Although cognitive problems are common in people with SPMS and PPMS, the researchers noted that these groups are often underrepresented in studies. This is partly because there are fewer treatment options for these forms of MS, and physical disabilities can make it difficult for patients to participate in long-term research. As a result, most studies focus on RRMS, in which symptoms are milder, leading to gaps in understanding how cognitive abilities change in other types of MS.
To investigate the differences, the researchers recruited 88 participants, 22 in each of four MS subtypes – RRMS, SPMS, PPMS — as well as healthy controls. Participants completed a variety of cognitive tests and reported on symptoms of fatigue, depression, and anxiety. One year later, they went through the same process, providing two snapshots of these measurements.
Some demographic characteristics differed significantly among groups at the beginning of the trial. PPMS participants, with a mean age of 53.27, were the oldest. Time since the disease started and time since diagnosis was different across MS types, with SPMS patients having had the disease the longest. SPMS patients also had the most physical disability. The groups were similar in gender and education.
The team statistically corrected for differences in age and education, which could affect cognitive scores.
Participants across all MS subtypes tended to have worse cognitive function, depression, and fatigue than controls. This was true at both time points. During the second test, the most substantial differences between the control and MS groups were in fatigue and executive function, or the ability to regulate thoughts and emotions.
At both time points, “progressive MS forms exhibited more pronounced and widespread cognitive impairments than RRMS,” the researchers wrote. These included significantly lower global cognition scores, a composite metric the team developed based on all cognitive assessments combined. When compared with the control group, participants with progressive forms of MS also showed significantly more depressive symptoms, had higher levels of fatigue, and had more difficulty with tasks requiring attention.
Fatigue, mental health, thinking ability
At the beginning of the study, RRMS patients showed a significant link between fatigue and both mental health issues and thinking abilities. PPMS patients also showed a significant connection between fatigue and mental health, but not with thinking abilities. SPMS patients didn’t show any clear links between these areas.
At follow-up, all three MS subtypes — RRMS, SPMS, and PPMS — showed a significant link between fatigue and mental health. However, no connections were found between thinking abilities and either fatigue or mental health in any group.
“The complex interrelationship between cognitive impairment and psychological factors suggests that stabilizing mental health and fatigue may attenuate cognitive decline in MS,” the researchers wrote.
Comparing scores at the two time points revealed treated participants with RRMS significantly improved in multiple areas. These included global cognition, episodic memory, and attentional function. PPMS participants also showed improvement in their global cognition, as well as their ability to visually process spatial relationships. There were no significant changes in the group with SPMS.
For the RRMS and PPMS groups, “the reason for this improvement is unclear and confirmatory data are required,” the researchers wrote.
With their relatively small number of participants, the team cautioned against applying these results too broadly. They also noted that people in the MS groups were on a variety of different MS treatments during the year between measurements. Different therapeutic approaches could have affected cognitive symptoms, they said.
The researchers said the differences they found between the progressive MS groups and people with RRMS, particularly related to depression and fatigue, suggest that “combined treatment approaches should address both cognitive rehabilitation and emotional well-being.”
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