Increase in kawasaki disease incidence observed in 30-year population-based study in scandinavia

ABSTRACT

Background and Aim: World-wide, Kawasaki disease (KD) is known to affect predominantly children under the age of 5, mostly boys. An increasing incidence has been reported from select countries, as well as seasonal differences, although with great variation among reports. Sweden has unique population-based health registers which can be linked to population registers via a personal number. In this study we therefore utilized population-based data over a period of more than 30 years to investigate demographics and epi-demiology of Kawasaki disease in a Scandinavian country. Method(s) Individuals receiving a diagnosis of Kawasaki disease in Sweden from 1987-2018 (before the occurrence of MIS-C) were identified by ICD9 and ICD10 discharge diagnoses in the Patient register at the National Board of Health and Welfare, and basic demographic information obtained by cross-linking with popula-tion registers at Statistics Sweden. Age-stratified population statis-tics were also retrieved during the corresponding time-period. Result(s) A total of 1,785 individuals with a KD diagnosis during the study period were identified, confirming a relatively low incidence in the Scandinavian population. Less than 5% of the cases were born in another country. The majority of cases (78%) occurred before 5 years of age, and there was a male dominance (61%). Sweden has a temperate climate of the northern hemisphere, and analysis of case distribution over the yearly cycle revealed peak incidence during the winter months. Notably, the incidence rose from around 6/100,000 lt;5-year-olds to 15/100,000 lt;5-year-olds during the 30-year study period. Two years with prominently higher incidence than prior and following years were observed. A large part of the rise in incidence seems to be associated with immigration and occurred before the occurrence of Multisystem Inflammatory Syndrome in Children related to SARS-CoV-2. Conclusion(s) Demographic parameters for Kawasaki disease in Sweden regarding age and sex distribution are similar to previous reports from other countries. Our data from a 30-year study period of population-based observations confirm peak incidence during the cold period, and a rising incidence during recent years, even before the occurrence of MIS-C. Our data also indicate outbursts during two years and immigration-associated patterns in rise in incidence.