OBJECTIVE: The prevalence of multimorbidity is socially patterned, but little is known about how socioeconomic inequality might affect the long-term progression of multimorbidity. This study aimed to identify multimorbidity trajectories and to examine their association with socioeconomic status (SES) among middle-aged and older Chinese adults.
METHODS: A total of 3837 middle-aged and older participants were included from the dynamic cohort of the China Health and Retirement Longitudinal Study, 2011-2018. Multimorbidity trajectories were assessed using the Chinese Multimorbidity-Weighted Index (CMWI), which covers 14 chronic conditions. Group-based trajectory modeling was used to identify multimorbidity developmental trajectories. Education, working status, and total household income were used to construct SES scores. The associations between SES and CMWI trajectories were estimated using multinomial logistic regression models adjusting for sociodemographic and lifestyle factors.
RESULTS: Four distinct CMWI trajectories were identified: 'no multimorbidity' (16.8 %), 'new-onset multimorbidity' (48.7 %), 'slowly increasing multimorbidity' (24.3 %), and 'rapidly increasing multimorbidity' (10.2 %). Lower SES was associated with higher odds of experiencing the 'rapidly increasing' trajectory (P < 0.01); for example, compared with the 'no multimorbidity' group, participants with low SES had a 96 % (OR, 1.96; 95 % CI, 1.29 to 2.98) increased odds of belonging to the 'rapidly increasing' group.
CONCLUSION: Socioeconomic inequalities were observed in the CMWI trajectories of multimorbidity in middle-aged and older Chinese adults. The findings suggest effective strategies for preventing and controlling multimorbidity should be made from a long-term perspective, especially for those of lower SES.
