Prevalence of and risk factors for asthma among people aged 45 and older in China: a cross-sectional study

Background: Asthma is one of the most prevalent chronic respiratory diseases worldwide. This study aimed to determine the updated prevalence of and risk factors for asthma among individuals aged 45 and older in mainland China.

Methods: The data for this study came from the fourth wave of the China Health and Retirement Longitudinal Study (CHARLS) conducted by the National School of Development of Peking University in 2018. The CHARLS is a nationally representative survey targeting populations aged 45 and over from 28 provinces/cities in mainland China. A representative sample of 19,816 participants was recruited for the study using a multistage stratified sampling method. The prevalence of asthma was determined across different characteristics. The potential risk factors were examined by multivariable logistic regressions.

Results: A total of 18,395 participants (8744 men and 9651 women) were eligible for the final data analysis. The estimated prevalence of asthma among Chinese people aged ≥ 45 years in 2018 was 2.16% (95% CI 1.96-2.38). The prevalence of asthma significantly differed according to race (P = 0.002), with an overall rate of 2.07% (95% CI 1.86-2.29) in Han paticipants and 3.32% (95% CI 2.50-4.38) in minority participants. Furthermore, the minority ethnicities (OR = 1.55 [95% CI 1.12-2.14], P = 0.008), older age (60-69 years group: OR = 1.85 [95% CI 1.17-2.92], P = 0.008; ≥ 70 years group: OR = 2.63 [95% CI 1.66-4.17], P < 0.001), an education level of middle school or below (middle-school education: OR = 1.88 [95% CI 1.15-3.05], P = 0.011; primary education: OR = 2.48 [95% CI 1.55-3.98], P < 0.001; literate: OR = 2.53 [95% Cl 1.57-4.07], P < 0.001; illiterate: OR = 2.78 [95% CI 1.72-4.49, P < 0.001]), smoking (OR = 1.37 [95% CI 1.11-1.68], P = 0.003), and residence in North (OR = 1.52 [95% CI 1.11-2.09], P = 0.01) or Northwest China (OR = 1.71 [95% CI 1.18-2.49], P = 0.005) were associated with prevalent asthma.

Conclusions: Asthma is prevalent but underappreciated among middle-aged and elderly people in China. A number of risk factors were identified. These results can help to formulate correct prevention and treatment measures for asthma patients.