Trajectories of health-related quality of life by change pattern of objective and subjective social status.

Long-term and cumulative social experiences influence an individual's objective and subjective social status. Social determinants of health are more effectively investigated by longitudinal rather than cross-sectional studies. The primary focus of this study was the prospective effect of socioeconomic transition on health-related quality of life trajectories. The study population were adults over 18 years of age who responded in all nine waves of the Korea Health Panel (2009-2017). Data were analyzed by group-based trajectory modeling to identify health trajectories, and group-based multi-trajectory modeling to investigate combined change patterns of objective and subjective social status (i.e., multi-SES trajectories). To predict the effects of underlying socioeconomic measures on health trajectory group membership, we included these time-stable covariates in trajectory modeling and estimated the risk of belonging to each trajectory based on the measures. The health-related quality of life trajectories showed three patterns during the period 2013 to 2017; 13.7% of individuals had a low and declining health trajectory and the others had a higher stable health trajectory. Four types of multi-SES trajectory were derived during the period 2009 to 2013; the richer had a steeper income slope while there were slight changes in subjective social status among all groups. These combined longitudinal SES patterns in 2009-2013 were strong predictors of subsequent health trajectory group membership in 2013-2017. These findings indicate that rich countries, such as South Korea, may encounter growing income inequality, where individuals become entrenched in income disparity that pins down their perceptions of social position. Over time this rigid social structure will widen the gap in health-related quality of life.