Patterns and trends in asthma incidence rates in main Asian and Western countries and their prediction to 2030.

Background: The urbanization and industrialization of East and Southeast Asia in decades past has significantly altered living environment and lifestyles, which may have complicated effects on the burden of asthma. We aim to examine the patterns and trends of asthma incidence rates in six major East and Southeast Asian countries as well as five major Western countries, and predict the numbers of new cases attributed to various factors. Methods: Data on annual asthma incident cases and corresponding population by age group were drawn from 6 major selected East and Southeast Asian countries available in the Global Burden of Disease database, including China, Japan, Korea, Singapore, Philippines, and Thailand. We also collected data of five major high-income Western countries for comparative purposes. Two separate Bayesian age-period-cohort models, representing pre-COVID (model 1) and post-COVID (model 2) scenarios, were constructed to predict the asthma incidence until 2030. Results: In model 1, the age-standardized incidence rate of asthma will be the highest in the US (1970.07 per 100,000, 95% confidence interval [CI] 533.05-4455.03), while the lowest incidence rate will be found in Singapore (296.72 per 100,000, 95% CI 135.16-899.55) in 2030. Between 1990 and 2030, the incidence of asthma is projected to increase in China and Thailand, with average annual percentages changes (AAPC) ranging from 0.70% to 1.80%. The remaining four Asian countries show a declining trend, with AAPC ranging from -0.51% to -2.00%. In model 2, the US is estimated to have the highest age-standardized incidence rate (902.71 per 100,000, 95% CI 375.44-2277.24), while Korea will have the lowest incidence rate (176.46 per 100,000, 95% CI 58.77-512.09) in 2030. A decrease in asthma incidence was observed in all countries with the overall AAPC ranging from -3.42% to -0.42%. Notably, a turning point was found around 2020, after which the incidence rates dropped significantly. Conclusions: Pandemic-related factors may temporarily lower the incidence of asthma. The expected increasing asthma incidence in pre-COVID scenario (model 1) should still warrant attention from public health practitioners and call for efforts to reduce the burden of asthma.