Using repeated biological measurements from thousands of participants, researchers from the University Medical Centre Groningen and the Faculty of Economics and Business of the University of Groningen show that individuals with lower socioeconomic status exhibit higher levels of cumulative biological strain from their twenties onward. These differences widen with age, suggesting that socioeconomic health inequalities are not sudden outcomes of later-life disease, but the result of long-term physiological processes unfolding across the life course.
Central to the study is the construction of an allostatic load index (ALI), a composite measure based on twelve objective physiological indicators, including blood pressure, lipid profiles, glucose metabolism, and inflammatory markers. Rather than focusing on diagnosed disease, the ALI captures early biological dysregulation, often described as the “wear and tear” on the body resulting from prolonged exposure to stress.
The analysis reveals a clear socioeconomic gradient: lower-educated individuals consistently show higher ALI scores than their higher-educated counterparts. These disparities are observable in young adulthood and increase steadily over time.
Health-related behaviors such as smoking, alcohol consumption, physical activity, and body weight explain part of the observed differences, but not all. Even after adjusting for these factors, substantial socioeconomic gaps in allostatic load remain. This indicates that structural and contextual factors — including working conditions, financial insecurity, and chronic psychosocial stress — play an independent role in shaping biological health trajectories.
The findings challenge explanations of health inequality that focus primarily on individual lifestyle choices. Instead, they point to the cumulative impact of social and economic conditions on physiological functioning over time.
Higher allostatic load is strongly associated with increased risks of chronic disease and premature mortality, underscoring the importance of early identification and prevention. By using objective biological measures, the study demonstrates that health inequalities are often detectable long before clinical symptoms arise.
According to the authors, these results highlight the need for early-life and early-adulthood interventions that address both health behaviors and broader socioeconomic circumstances. Policies aimed solely at older populations may come too late to alter long-term health trajectories.
The study draws on data from Lifelines, a large population-based biobank and cohort study in the Netherlands that has followed nearly 170,000 individuals across three generations since 2006. Lifelines is an initiative of the UMCG and the University of Groningen. Participants undergo comprehensive physical examinations every five years and complete detailed questionnaires approximately every 18 months, covering health, lifestyle, and social conditions, making Lifelines the longest running population-based cohort worldwide with such systematically repeated, long-term measurements. All measurements are conducted according to standardized medical protocols, providing a uniquely rich resource for life-course health research.
The article Lifetime Trajectories and Drivers of Socioeconomic Health Disparities | Journal of Human Resources was written by Jochen Mierau and Gerard van den Berg from UMCG, and Ailun Shui and Laura Viluma from the Faculty of Economics and Business at the University of Groningen (RUG).
