High incidence, prevalence of pediatric-onset MS in Sweden

Sweden has a consistently high incidence and prevalence of pediatric-onset multiple sclerosis (PoMS), according to a recently published study.

Incidence measures the number of new cases identified during a certain period, while prevalence measures the proportion of people in the population with the condition. Data show the disease is more common in females and in patients aged 16 or 17. For every two females with PoMS, there is nearly one male with it, overall.

“Our results are valuable not only for the Swedish health care system and economy but also for the planning and implementation of clinical trials for POMS, which are urgently needed for this vulnerable patient group,” the researchers wrote in “Incidence rate and prevalence of pediatric-onset multiple sclerosis in Sweden: A population-based register study,” which was published in the European Journal of Neurology.

MS occurs when the immune system mistakenly attacks the myelin sheath, a protective coating around nerve fibers that helps them send electric signals more efficiently. Damage or loss of myelin leads to impaired nerve function, resulting in the disease’s symptoms.

While MS usually occurs in adults, it can also affect those younger than 18. Children with PoMS have a higher rate of relapses and a faster accumulation of lesions than those with adult-onset MS. This results in physical and cognitive issues that lead to high rates of healthcare use. It’s important to know how frequent PoMS is to be able to plan allocating resources for these patients, but “such studies are scarce, few are population-based, and the methodology varies widely,” wrote researchers in Sweden, who identified PoMS cases by using the National Patient Register and the Swedish MS Registry.

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Incidence, prevalence rates of PoMS

Sweden is known for a high MS incidence and prevalence. Both were estimated every year from 2006 to 2016 and 238 cases of PoMS were identified, mainly in females (69%), with patients having a median age at onset of 16.4. This corresponded to an overall incidence during the study period of 1.12 per 100,000 person-years and a prevalence of 2.82 cases per 100,000 people within the population. Person-years measures the total number of patients and the amount of time each person spends in a study.

Incidence was highest in the older group (16-17) with a rate of 5.31 per 100,000 person-years, followed by 1.94 per 100,000 person-years in children ages 12-15. The incidence rate in children younger than 12 was 0.09 per 100,000 person-years.

Taking children 12-15 as reference, the incidence rate was 2.73 times higher in ages 16-17 and significantly lower in children under 12.

Also, incidence was 2.4 times higher in females than males, with a significantly higher preponderance of females in the two older age groups, but not the youngest. The overall prevalence was also about two times higher in females than males.

When adjusted for age group and/or sex, results showed an annual 18% decrease in prevalence among children younger than 12. In contrast, there was an annual 5% increase among patients 16 or 17. There were no significant changes over time in the overall study population, however.

The estimated high incidence rate and prevalence of PoMS in Sweden remained stable over time. “This knowledge serves as a tool to aid in planning resource allocation and health services for this patient population,” the researchers said.