Low-to-moderate atmospheric ozone levels are negatively correlated with hospital visits by asthma patients

Asthma is a chronic illness of the airways that affects approximately 300 million individuals worldwide. While it is commonly accepted that high ozone levels exacerbate asthma symptoms, the impact of low to moderate ozone levels on asthma symptoms has received little attention. The purpose of this research was to determine the relationship between hospital visits by asthma patients showing the severity of their symptoms and moderate ozone levels. Statistical analyses were performed on hospital visit big data for asthma patients in Seoul, Korea, collected between 2013 and 2017. The data set includes outpatient hospital visits (n = 17,787,982), hospital admissions (n = 215,696), and emergency department visits (n = 85,482). The frequency of hospital visits by asthma patients was evaluated in relation to low ozone levels (< 0.03 ppm) and moderate ozone levels (0.03–0.06 ppm) in the Seoul environment. In comparison to low ozone levels, moderate ozone levels resulted in a reduction in outpatient hospital visits (t = 7.052, P < .001). When ozone levels were low to moderate, there was a negative correlation between ozone levels and outpatient visits (r = −0.281, 95% CI: −0.331 to −0.228). Negative associations were also identified between ozone levels and new hospital admissions (t = 2.909, P < .01; r = −0.125, 95% CI: −0.179 to −0.070) and emergency treatments (t = 2.679, P < .01; r = −0.132, 95% CI: −0.186 to −0.076). Additionally, it was verified that moderate ozone levels one day before the visits resulted in a reduction in outpatient visits (t = 5.614, P < .001; r = −0.207, 95% CI: −0.259 to −0.153). A strong relationship was identified between moderate atmospheric ozone levels and a reduction in asthma patient hospital visits.