The finding confirmed a long-held assumption that the more progressive form of the disease — SPMS — also involves more cognition problems. Some previous research has confirmed that hypothesis, but other studies have contradicted it.
The Greek team’s article, “Cognitive and Language Deficits in Multiple Sclerosis: Comparison of Relapsing Remitting and Secondary Progressive Subtypes, appeared in The Open Neurology Journal.
Neurocognitive impairment affects between 40 and 65 percent of MS patients. The impairment occurs regardless of the stage of the disease, how long a person has had it, and the severity of their physical disability. And it worsens over time.
Researchers have done a number of studies on whether cognition is worse in different forms of the disease than others, but the findings have been contradictory.
A team at the University of Patras hoped to shed more light on the subject. They evaluated the cognitive and linguistic functioning of 27 patients — 15 with RRMS and 12 with SPMS. They also assessed 12 healthy volunteers as controls.
All participants took a battery of neuropsychological and language tests.
Both categories of MS patients showed worse cognition than healthy volunteers — a finding that confirmed the results of previous studies.
A key finding was that the SPMS patients had cognition problems in all areas they were tested for. Meanwhile, RRMS patients had impairments in three categories — initial verbal word encoding, word consolidation, and delayed recall of verbal information.
Interestingly, researchers found no differences in verbal fluency between RRMS patients and healthy people, suggesting that this function is affected only at later stages of the disease.
The results of the various tests also revealed that SPMS patients’ impairments were more severe. This was particularly true with verbal encoding and processing new items. In addition, SMPS patients had poorer mental processing speed.
Another difference was that SPMS patients also had significantly worse performance in tests of executive function, which deal with behavior, than RRMS patients.
The researchers said the findings “confirm the assumption that MS patients, irrespective of the clinical subtype, have more severe deficits than healthy participants, which become increasingly worse as the severity of the disease proceeds and RRMS patients convert to SPMS.”
“Thus, the hypothesis that the progressive type of disease shows a relatively greater reduction in cognitive function, compared to the RRMS type, was confirmed,” the team wrote.
The two groups showed similar patterns of global cognitive function, however, the researchers wrote. Global cognition involves learning, thinking critically, and interacting with others effectively.
“Although they do not differ on overall global cognitive function, they differ on important cognitive abilities such as learning new information, speed of mental processing, ability to inhibit overlearned responses and mental flexibility,” the team wrote. “These cognitive deficits have a significant impact on everyday functioning abilities and quality of life.”