Abstract: 【Abstract】 Objective To analyze trends in urticaria incidence among children aged 0 - 14 years in China from 1990 to 2021, to explore its changing patterns in different age, period, and cohort groups, and to investigate the impact of age and air pollutants on the incidence trends. Methods Data were obtained from the Global Burden of Disease Database （GBD2021）, including the number of urticaria cases, crude incidence rates, and age-standardized incidence rates among children aged 0 - 14 years of different genders in China from 1990 to 2021. The Joinpoint regression model was used to calculate the annual percentage change （APC） and average annual percentage change （AAPC） to assess temporal trends in incidence rates. An age-period-cohort model was applied to assess the effects of age, period, and cohort on urticaria incidence. Data on the annual emissions of 4 air pollutants （SO?, CO, PM?.?, and PM??） in China from 1990 to 2021 were obtained from the Emissions Database for Global Atmospheric Research （EDGAR）, and a multivariable meta-regression model was used to explore the relationship between air pollutants and urticaria incidence. Results From 1990 to 2021, the age-standardized incidence rate of urticaria among children aged 0 - 14 years in China demonstrated a slight overall downward trend （AAPC = -0.03%, P < 0.01）. The incidence rate was generally higher in female children than in male children, and the decline in incidence rates was greater in female children than in male children （female AAPC = -0.02%, male AAPC = -0.01%, both P < 0.01）. The age-period-cohort model indicated that the risk of urticaria decreased with advancing age: with the age group of 0 - 4 years as the reference （RR = 1.000）, the risk of urticaria significantly decreased in the age group of 5 - 9 years （RR = 0.790, 95% CI: 0.789 - 0.791） and further declined in the age group of 10 - 14 years （RR = 0.711, 95% CI: 0.710 - 0.711）; the period effect analysis showed that the risk of urticaria gradually decreased after the baseline period of 1992 - 1996 （RR = 1.000）, and dropped to 0.995 （95% CI: 0.994 - 0.997） in the period of 2017 - 2021; in the cohort effect analysis of the overall population aged 0 - 14 years, with the 1988 - 1992 birth cohort as the base cohort, an earlier birth cohort 1978 - 1982 exhibited the highest risk of urticaria （RR = 1.006, 95% CI: 1.004 - 1.009）, while the 2013 - 2017 cohort showed the lowest risk （RR = 0.996, 95% CI: 0.994 - 0.997）. The multivariable meta-regression analysis indicated a significant association between PM?.? exposure and urticaria incidence （β = 0.319, 95% CI: 0.022 - 0.616, P = 0.033）, although this association was not statistically significant in different age groups. Conclusions From 1990 to 2021, children aged 0 - 4 years in China were the highest-risk group for urticaria; the decline in the incidence rate of urticaria was more pronounced in female children than in male children, and earlier birth cohorts exhibited higher risks of urticaria. Exposure to PM?.? appeared to be associated with the incidence of urticaria.

Key words: Urticaria, Incidence, China, Child, Air pollutants, 0 - 14 years, Joinpoint regression model, Age-period-cohort model