An increased risk for multisystem inflammatory syndrome in children (MIS-C) has been associated with male sex, age 5 to 11 years, foreign-born parents, asthma, obesity, and life-limiting conditions, according to study findings recently published in The Lancet Regional Health – Europe.

Researchers for the current study sought to evaluate risk factors for MIS-C, with the ultimate goal of identifying vulnerable children. It is well known that although severe acute COVID-19 is rare among children, infection with SARS-CoV-2 can trigger the novel postinfectious MIS-C. It has been recognized that increased knowledge about the risk factors for MIS-C could improve our understanding of its pathogenesis and help to better guide targeted public health interventions.

A population-based cohort study was conducted among all children and adolescents less than19 years of age who had been born in Sweden between March 1, 2001, and December 31, 2020. National health and population registers were used to obtain data on patient socioeconomic risk factors and comorbidities, including age, sex, parental region(s) of birth, parental level of education, asthma, autoimmune disease, chronic heart disease, chronic lung disease, chromosomal anomalies, obesity, and life-limiting conditions. The study outcome was defined as “MIS-C diagnosis according to the Swedish Pediatric Rheumatology Quality Register” during the study period.


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A total of 2,117,443 children were included in the study. Among them, 253 children developed MIS-C — which corresponded to an incidence rate of 6.8 (95% CI, 6.0-7.6) per 100,000 person-years.

Results of the study showed that the following variables were associated with MIS-C:
(1) male sex (hazard ratio [HR], 1.65; 95% CI, 1.28-2.14), (2) age 5 to 11 years (adjusted HR [aHR], 1.44; 95% CI, 1.06-1.95 [with the use of children 0 to 4 years as a reference), (3) foreign-born parents (HR, 2.53; 95% CI, 1.93-3.34), (4) asthma (aHR, 1.49; 95% CI, 1.00-2.20), (5) obesity (aHR, 2.15; 95% CI, 1.09-4.25), and (6) life-limiting conditions (aHR, 3.10; 95% CI, 1.80-5.33). Children between 16 and 18 years of age exhibited a decreased risk for MIS-C (aHR, 0.45; 95% CI, 0.24-0.85).

Several limitations of the current study warrant mention. Because limited SARS-CoV-2 testing has been performed among children and many children may have subclinical SARS-CoV-2 infections, the MIS-C estimates used in the current study were based on the whole population, not solely on those children who were infected with SARS-CoV-2. Further, because MIS-C is known to be a rare outcome, the researchers were unable to accurately examine less common comorbidities or to perform analyses that were stratified according to disease severity, in order to explore possible dose-response effects.

The investigators concluded that although the absolute risks for MIS-C reported in the current study were very low, knowledge of these risk populations might facilitate identification of children with the disorder and potentially guide targeted public health interventions.

Disclosure: Some of the study authors have declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 

Reference  

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