Timing of Maximum Educational Attainment, Life Course Income Patterns, and Multiple Chronic Medical Conditions at Midlife

Purpose: At midlife, educational attainment and life course income, among other indicators of socioeconomic class, are reliably and negatively linked to the risk of multi-morbid chronic medical conditions. When modeling these relationships, however, much research has used point-in-time measures (e.g., maximum level of education) or aggregated variables (e.g., mean adult income). These approaches potentially mask more nuanced relationships that may depend, for instance, on timing of educational attainment or various income trajectory patterns. Observing the presence of these relationships could increase knowledge of the mechanisms by which social and economic characteristics find expression in health. Further, this knowledge could be deployed to guide the development of direct service interventions and policies to delay onset or ameliorate the effects of multi-morbidity.

Methods: This study used data from 22 years of the National Longitudinal Survey of Youth, 1979. Upon turning 40, respondents (N=4,383) reported if they had any of nine chronic health conditions. Responses to these questions were transformed into a dichotomous dependent variable to describe individuals who reported zero or one condition or two or more. Using completion of college by 24 years of age as a reference category, three dummy variables were calculated (completion of college after 24 and before 40, high school diploma, and no high school diploma) to assess the effect of the amount and timing of education on multi-morbidity. A latent class growth analysis (LCGA) was used to classify participants’ reported incomes over the course of the study. These classes were similarly dummy-coded for analysis. Additional covariates adjusted for race or ethnicity, gender, parental education, smoking, and obesity.

Results: Interpretability of the LCGA and the Bayesian Information Criterion fit statistic suggested a five-class model of income trajectories. One large class (n=1,380, 32%) reported high incomes at all six assessed waves. An equally large class reported low incomes at each wave. Three smaller classes, a moderate class (n=942, 22%), an increasing class (n=319, 7%), and a class (n=250, 6%) with a curvilinear trajectory that decreased sharply after respondents turned 34 years old were identified. After covariate adjustment, respondents with high school diplomas or those completing college by 40 compared to those who completed college by 24 had, respectively, 0.45 and 0.71 higher log odds of multi-morbidity. Similarly, those with a uniformly low life course income or those with a curvilinear-decreasing trajectory had 0.90 and 0.45 higher log odds of multi-morbidity than those with consistently high incomes. Those with moderate or increasing incomes did not differ from those with high incomes.

Implications: These results suggest that level and timing of educational attainment and income trajectories may have long-term implications for health. As longevity increases in the U.S. population, preventing multi-morbidity at midlife and beyond is likely to be a core health priority. Though interventions to promote rapid college completion and increase or maintain incomes are rarely conceptualized in terms of potential health benefits, the findings of this analysis suggest that such interventions could be a sound public health investment, with positive consequences at multiple points along the life course.