Impact of multimorbidity on household expenditure in China: evidence from the China health and retirement longitudinal study

BACKGROUND: Multimorbidity poses a significant global economic burden, profoundly affecting individuals' standard of living and leading to substantial increases in healthcare expenditures. Understanding how households strategically adjust expenditures to cope with multimorbidity-induced financial strain-and how these strategies differ across economic groups-is a critical and understudied issue that demands immediate research attention. METHODS: This study employs data from the China Health and Retirement Longitudinal Study (CHARLS) for the years 2013, 2015, 2018, and 2020. We apply a panel Tobit regression model combined with K-means clustering analysis to examine the effects of the number of chronic diseases and associated multimorbidity patterns on the levels and structure of household expenditures. Additionally, Recentered Influence Function (RIF) regression is implemented to investigate how transitions from the absence of chronic diseases to single or multiple chronic diseases reshape household expenditure allocations across survival-related, medical, non-medical developmental, and recreational expenditure categories. FINDINGS: The presence of multiple chronic conditions is significantly correlates with a decrease in household survival expenditures and an increase in medical expenditures, while expenditures on non-medical development and enjoyment remain largely unaffected. Patterns including cardiometabolic syndrome, single-system joint diseases, multi-system chronic diseases, major organ-mental comorbidities, and extreme chronic conditions progressively reduce the proportion of household survival expenditures while increasing medical expenditure proportions. The transition from no chronic disease to single chronic condition significantly widens the disparity between household survival and medical expenditure proportions. However, this effect diminishes as individuals progress from a single chronic condition to multimorbidity. Heterogeneity analysis reveals that, compared to low-income households, high-income households experience a smaller increase in the proportion of medical expenditures and a smaller decrease in the proportion of survival expenditures, reflecting their greater advantages in consumption planning and financial flexibility, and their higher likelihood of simultaneously accumulating both health and wealth. Due to differences in economic development levels, households in the Eastern regions are more likely to adjust the proportion of survival expenditures in response to chronic diseases. Cardiometabolic syndrome pattern reduce survival expenditure proportions in Eastern/Central regions (vs. no impact in Western/Northeastern), while single-system joint disease pattern mainly affect Eastern/Western regions with milder Central effects. Poorer self-perceived health amplifies multimorbidity's negative impact on enjoyable expenditures. INTERPRETATION: By pinpointing how multimorbidity affects spending patterns, our study offers a novel perspective on the economic challenges families face. Multimorbidity compels households in rapidly developing countries to reallocate resources from basic survival needs toward medical care to manage health shocks. Low-income families, with limited financial flexibility, are compelled to significantly reduce survival expenditures to maintain non-medical developmental expenditures, which may lead to unequal development opportunities across different income groups. Efforts should be continuously made to improve infrastructure, public services, and financial support to better assist individuals and families affected by chronic diseases.