Swedish Study Identifies MIS Risk Factors Among Pediatric Patients

Multisystem inflammatory syndrome (MIS) in children is a rare condition known to be associated with COVID-19, but more research is needed to identify at-risk patients and guide public health interventions.

Multisystem inflammatory syndrome in children (MIS-C) is a rare but serious condition associated with SARS-CoV-2 infection, and there is a lack of population-based studies to determine MIS-C risk factors. A recent study published in The Lancet Regional Health – Europeaimed to characterize the risk factors for MIS-C using registry data that covered all children and adolescents in Sweden.

Severe acute COVID-19 in children is rare, but it is a known risk factor for MIS-C, which can cause acute heart failure, coronary artery dilation, or arrythmias and requires urgent immunomodulatory treatment. COVID-19 vaccination has been shown to reduce the risk of MIS-C. The current study aimed to identify vulnerable children and adolescents, which can help with the creation of targeted public health interventions and improve understanding of the pathogenesis of MIS-C.

The registry-based study included 2 million-plus children and adolescents younger than 19 years who were born in Sweden between March 2001 and December 2020. Data from national health and population registers were used to identify sociodemographic risk factors and comorbidities.

A total of 253 cases of MIS-C were reported during the study period, and the incidence rate was 6.8 per 100,000 person-years. Several characteristics were associated with a higher MIS-C risk: age, male sex, foreign-born parents, asthma, obesity, and life-limiting conditions.

The overall population included 556,872 children aged 0 to 4 years; 882,787 children aged 5 to 11 years; 401,044 children aged 12 to 15 years- and 276,740 children aged 16 to 18 years. Children in the 5- to 11-year age group had an adjusted (aHR) of 1.55 (95% CI, 1.06-1.95). Age-based risk assessment was done using children aged 0 to 4 years as reference.

Male sex carried an aHR of 1.65 (95% CI, 1.28-2.14), and children with foreign-born parents had an aHR of 2.53 (95% CI, 1.93-3.34). Asthma (aHR, 1.49; 95% CI, 1.00-2.20), obesity (aHR, 2.15; 95% CI, 1.09-4.25), and life-limiting conditions (aHR, 3.10; 95% CI, 1.80-5.33) also increased the risk of MIS-C. Conversely, children aged 16 to 18 years were less likely to have had MIS-C (aHR, 0.45; 95% CI, 0.24-0.85). From a sociodemographic standpoint, children with foreign-born parents had the highest absolute risk, with an incidence rate of 13 per 100,000 person-years.

The findings regarding overall incidence were similar to those of a cohort study based on CDC COVID-19 data and US Census data, which found that children aged 6 to 10 years had the highest risk of MIS-C. The authors also note that although the current study included the whole population and not just children with COVID-19, some of the risk factors for MIS-C identified in the study have also been associated with severe acute COVID-19.

“To conclude, we report that male sex, age 5 to 11 years, foreign-born parents, asthma, obesity, and life-limiting conditions were associated with increased risk for MIS-C in a large population-based cohort study with adjustments for important confounding factors, but the absolute risks were very low,” the authors wrote. “Knowing these risk populations might facilitate identification of children with MIS-C and potentially guide targeted public health interventions.”


Rhedin S, Lundholm C, Horne A, et al. Risk factors for multisystem inflammatory syndrome in children – a population-based cohort study of over 2 million children. Lancet Reg Health Eur. Published online June 22, 2022. doi:10.1016/j.lanepe.2022.100443

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