Kawasaki syndrome in Denmark

Objective: To describe the epidermologic characteristics of Kawasaki syndrome (KS) and to estimate national KS incidence rates among children in Denmark. Methods: A retrospective population-based study using hospital discharge records with a KS diagnosis for children younger than 15 years selected from I he Danish National Hospital Register for 1981-2004. Incidence rates were calculated using the number of KS patients and corresponding census data. Results: During 1981-2004, 360 children younger than 15 years were hospitalized with KS in Denmark, with 73% younger than 5 years. In this age group, the average annual incidence of KS gradually increased from 1981 to 1999 and thereafter stabilized at 4.5 to 5.0 per 100,000 person-years. The incidence was greater for boys than for girls (RR = 1.6, 95% Cl = 1.2-2.0) and was highest among infants younger than I year (4.5), declining with increasing age (P = 0.03). However, the age-specific decline in incidence was only observed for boy;;, whereas the incidence for girls remained unchanged by age. The median length of hospital stay was 12 days, and the incidence peaked in the winter months. Conclusions: Major epidemiologic characteristics identified among Danish childhood KS we consistent with those described in previous studies, such as highest incidence among young children and winter-seasonality. The KS incedence rate among children younger than 5 years in Denmark increased steadily during the early study period (coinciding with global recognition of KS) and seems to have stabilized from 1998-1999 onwards. Although the incidence among Danish children was lower than that reported for several other European countries, diffierences in methodology challenge definite comparisons.