1. Short-term increases in concentrations of air pollutants, sulfur dioxide (SO2) and particulate matter≤2.5 µm were positively associated with risk of Kawasaki disease diagnosis in this cohort of Korean children (aged 0 to 4).

Evidence Rating Level: 3 (Average)

Study Rundown: In children under 5, Kawasaki Disease (KD) is a leading cause of acquired heart disease, and predominantly occurs in Pacific Islander/Asian youth. Despite its high rates in these groups, its underlying etiology remains unknown. Some evidence suggests that respiratory triggers, including dust may cause inflammation in susceptible airways. This time-stratified case-crossover study aimed to determine the association between ambient air pollution exposure and future development of KD in Korean preschool-aged children. In total, 51 486 children with KD aged 0 to 4 who lived in regions with air pollution monitors were included. The researchers found significant positive associations between KD and interquartile range increases of the air pollutants, particulate matter ≤2.5 µm diameter and sulfur dioxide. While these results suggested a role of increasing air pollutants in development of KD, clinical correlation was limited by unavailable laboratory markers of inflammation for disease progression. Further studies will be necessary to validate and clinically correlate these results.

Click here to read the study in JAHA

Relevant Reading: Clustering and climate associations of Kawasaki Disease in San Diego County suggest environmental triggers

In-Depth [Case-Control Study]: This study included patients from the National Health Insurance System, a public data source covering nearly all citizens in South Korea. Air pollution data from 2007 to 2019 was retrieved from the National Institute of Environmental Research. The concentrations of particulate matter ≤ 10 µm (PM10) and 2.5 µm (PM2.5), carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and ozone (O3) were measured from 235 monitoring sites. In addition, a maximum of 8-hour moving averages were determined for CO and O3. Weather condition reports from 510 weather stations were also analyzed to adjust the association, including averages of ambient temperature and relative humidity. For the cases, three control days on the same day of the week within the same month as the day of KD diagnosis were selected, which would determine air pollution exposure within the same month of the event. Finally, the lag pattern in the effects was investigated with lags of 1 and 2 days to determine the duration of the critical exposure period for KD. Most enrolled patients (58.2%) were male, and most lived in Seoul Metropolitan Area and nearby cities. Most air pollutant concentrations, except for O3, decreased over the duration of the study. The concentrations of the PM10 and PM2.5 were 47.99 and 25.04 µg/m3 respectively, while mean NO2, SO2 and O3 were 26.34, 4.92 and 37.40 ppb and mean CO was 0.64 ppm. Within the model adjusting the KD association with air pollutants for temperature, statistically significant positive associations were found for lag 1; PM2.5 (OR 1.016; 95% CI, 1.004-1.029) and SO2 (1.022; 95% CI, 1.005-1.038). There was also an association with increase in sulfur dioxide concentration and KD across all lag days (OR, 1.018; 95% CI, 1.002–1.034 at lag 0; OR, 1.022; 95% CI, 1.005–1.038 at lag 1; OR, 1.017; 95% CI, 1.001–1.033 at lag 2). Generally positive associations were found for the other air pollutants.

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