Abstract
BACKGROUND: In China, catastrophic health expenditure (CHE) is a predominant factor that drives households into poverty. While commercial health insurance (CHI) can mitigate the adverse consequences of CHE, its uptake remains limited. This study aimed to analyse the association between CHE and the purchase of CHI in China from an ex post perspective. METHODS: This study included 34,534 observations from data from the 2019 China Household Finance Survey. A two-part model was employed to analyse the association between CHE (categorized as none, mild, moderate, or severe) and individual CHI purchase (both purchase behaviour and premium expenditure), guided by an integrated framework. Subgroup analyses were conducted to compare factors influencing CHI purchase between observations with and without household CHE. RESULTS: The prevalence rates of mild, moderate, and severe CHE were 19.27%, 6.97%, and 6.89%, respectively. The overall CHI purchase rate was 4.48%. Severe CHE was negatively associated with the likelihood of purchasing CHI (OR = 0.475, p < 0.01), whereas moderate CHE was negatively associated with premium expenditure among purchasers (coef.=−1.227, p < 0.05). Ambiguous risk preference was negatively associated with both the likelihood of purchasing CHI and premium expenditure. Factors such as poor self-rated health, older age (≥65 years), male sex, and lack of financial attention were negatively associated with the likelihood of purchasing CHI. Greater educational attainment and a stronger social support network were positively associated with the likelihood of purchasing CHI. Subgroup analyses revealed that the influencing factors of CHI purchase systematically differed between observations with and without household CHE. CONCLUSIONS: CHE is negatively associated with CHI purchase. The government should establish a full-cycle risk protection mechanism for vulnerable groups by deepening health care reform, implementing targeted subsidies, and enhancing public awareness. It is equally important for insurance institutions to improve the accessibility of CHI. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12913-026-14181-2.