Trend of asthma prevalence and risk factors in the 20s age band in South Korea.

Background: The prevalence of asthma has increased in many countries. However, whether asthma prevalence may only be true in a specific age band is not well known. Thus, we analyzed the increase in asthma prevalence according to age band and analyzed the related factors. Methods: We analyzed the trend of asthma prevalence according to 10-year age band intervals by using 2007 to 2018 data from the Korean National Health and Nutrition Survey. We determined the presence of subject-reported, physician-diagnosed asthma in 89,179 subjects. Multiple logistic regression analyses with a complex sample design were conducted to identify the risk factors for asthma. Results: Among all age ranges, only the 20s age band showed an increase in the trend of asthma prevalence from 0.7% in 2007 to 5.1% in 2018 (P<0.001 for joinpoint regression). Among the 7,658 subjects in the 20s age band, 237 (3.1%) subjects were asthma. In asthma group, 54.9% were male, 43.9% were ever-smokers, 44.6% had allergic rhinitis, 25.3% had atopic dermatitis, and 29.1% were obese. Multiple logistic regression analysis showed that asthma was related to allergic rhinitis [odds ratio (OR), 2.78; 95% confidence interval (CI): 2.03-3.81] and atopic dermatitis (OR, 4.13; 95% CI: 2.85-5.98), but not to male sex, ever-smoking, obesity, or socioeconomics status. Conclusions: From 2007 to 2018, the prevalence of asthma significantly increased in the 20s age band in South Korea. This may be related to the increase in the cases of allergic rhinitis and atopic dermatitis.