People with pediatric-onset multiple sclerosis (POMS) have a greater decline in cognitive function, and are more likely to experience cognitive impairment in adulthood, than those whose disease began when they were adults, a study reports.
The study, “Long-term Cognitive Outcomes in Patients With Pediatric-Onset vs Adult-Onset Multiple Sclerosis,” was published in the journal JAMA Neurology.
POMS, defined as MS that occurs before a person is 18 years old, accounts for between 2 and 10% of people with the neurodegenerative disorder. It’s known that there are some differences in how the disease tends to manifest in those affected as children compared with those with adult-onset multiple sclerosis (AOMS). Children with POMS are more likely to have more inflammation and disease activity early on.
Cognitive impairment affects both POMS and AOMS patients, and has been shown to be present in approximately a third of children with pediatric-onset MS. But, researchers asked, what about people with POMS who grow up to be adults with MS? How might cognitive impairment be different among adults with MS whose disease started when they were children, compared with those with MS whose disease began when they were adults?
Researchers assessed data from 5,704 MS patients — 300 with POMS, and the remaining with AOMS — who had at least two available scores on the Symbol Digit Modalities Test (SDMT), a measurement of cognition that has been validated for people with MS. The lower the score, the poorer is the patient’s cognitive function.
The included patients were predominantly female (70.4%). There were no significant differences in sex ratio, disease course, region of residence, or baseline SDMT score between the POMS and AOMS groups.
People in the POMS group were, by definition, younger at the time of diagnosis. They also tended to be younger at the time the first SDMT score was recorded.
Importantly, POMS patients who were still younger than 18 were not included in the study, so the comparisons made were strictly between adults whose disease had begun earlier or later in life.
Generally, SDMT scores between the two groups were similar in patients younger than 30 years old. However, after that age point, the scores diverged, with people with POMS having a sharper decline in scores than those with AOMS. For instance, at 35 years old, the mean SDMT scores were 60.9 for AOMS patients and 51.1 for POMS patients. By age 40, mean scores were 57.5 for those with AOMS as compared with 46.4 for those with POMS.
The researchers used statistical models to adjust the data for possible confounding factors, or variables that were not controlled or eliminated, that could damage the validity of the results. However, the differences remained.
“[T]he SDMT scores of patients with POMS consistently declined faster than those of patients with AOMS … independent of age, disease duration, or treatment status,” the researchers said.
Furthermore, 147 out of 208 (70.7%) POMS patients met the criteria for cognitive impairment, as compared with 2,305 of the 3,852 (59.8%) people with AOMS. That’s a statistically significant difference that held even when other factors, including disease course and the use of disease-modifying treatments, were taken into account.
As a limitation of the study, the researchers noted that no test can encapsulate every aspect of cognition. They emphasized that the SDMT focuses on information processing, but not memory or executive function.
Nonetheless, overall, the data suggested that POMS patients are more likely than people with AOMS to experience cognitive impairment as adults.
“Children and adolescents who develop MS should be monitored closely for cognitive changes, and helped to manage the difficulties and challenges that MS poses on scholastic and work-related achievements, with a view to the long-term consequences of MS as they reach adulthood,” the researchers said.
“Further investigation is required to better understand the biological and psychosocial mechanisms by which an early onset of MS influences cognitive outcomes and to establish appropriate interventions and treatment guidelines,” they added.