The modification effect of concentration on the correlation between ambient ozone and psoriasis: a hospital-based...

The effects of short-term ambient ozone (O₃) exposure on health outcomes have received growing concerns, but its effects on psoriasis is still unclear. The purpose of our study was to investigate the effects of short-term exposure to O₃ on psoriasis, and to find out potential modifiers. A hospital-based time-series study with outpatient visit data of psoriasis was performed in Chongqing, the largest metropolitan in Southeast China. General additive models combined quasi-Poisson regression were implied to reveal the association between short-term exposure to O₃ and psoriasis. Moreover, the potential modifiers were found out through subgroup analyses. Totally, 23,921 psoriasis outpatient visits were included. For the whole patient population, no significant association between exposure to O₃ and outpatient visits for psoriasis was observed. Interestingly, the stratified analyses based on concentrations showed that low concentration of O₃ (below the recommended limitation of 100 μg/m³ by WHO and China), rather than high concentration of O₃, was negatively associated with psoriasis outpatient visits at various lag days, and the greatest decrease was observed at lag03 (-2.05%; 95%CI: -3.55%, -0.53%). Moreover, stronger associations were observed in cool seasons, patients aged 40 or above, and males. Additionally, the negative associations of low-concentration O₃ on psoriasis outpatient visits were still robust in sensitivity analyses. Our study discovered that low-concentrations of O₃, rather than high concentrations of O₃, can be associated with decreased outpatient visits for psoriasis, especially for males, population aged 40 and above, and in cool seasons.