Women Are Leading the Socioeconomic Gradient Transition in Non-Communicable Diseases in China: Longitudinal National Data Analysis Between 1991 and 2020

OBJECTIVES: Non-communicable diseases (NCDs) pose a great health burden globally. Existing literature has established the association between Socioeconomic status (SES) and the development of non-communicable diseases (NCDs). The term "reversal hypothesis" has been attached to the observation that the SES gradient of NCDs tends to reverse over time. We examined this hypothesis in China between 1991 and 2020, to test whether a divergence in the experiences of men and women can be identified and to explore the possible contributors to any disparity identified.

METHODS: Using nine waves of China Health and Nutrition Survey (CHNS, 1991-2015) and six waves of the China Family Panel Studies (CFPS, 2010-2020), we investigated the SES-NCD gradient among participants aged 18 years and older. We estimated the relationship between self-reported doctor diagnosed NCDs and SES proxied by formal educational years by gender using multivariable logistic regression and Blinder-Oaxaca decomposition models.

RESULTS: Prevalence in the overall population of a list of NCDs increased from 3.52% (1991) to 13.72% (2020). The association between SES and NCDs has shifted from positive to negative over time, shifting earlier among women compared to men. For both men and women, the difference in prevalence between high and low SES groups was mostly explained by the socio-demographic and risk behaviour variables included in the models: age, employment, household income, residency and being overweight. However, the contribution size of these factors was different by gender and changed over time.

CONCLUSIONS: China has experienced a reversal in the SES gradient of NCDs which occurred first among women. The explanations of SES differences are complex and differ by gender. Health systems need to adapt and evolve the strategies to develop the gender-specific dynamic interventions to address the emerging socioeconomic disparities in NCDs.