Socioeconomic disadvantage, chronic stress, and proinflammatory phenotype: an integrative data analysis across the lifecourse.

Socioeconomic disadvantage confers risk for many chronic illnesses, and theories have highlighted chronic psychological stress and alterations to inflammatory processes as key pathways. Specifically, disadvantage can heighten chronic stress, which may promote a proinflammatory phenotype characterized by immune cells mounting exaggerated cytokine responses to challenge and being less sensitive to inhibitory signals. Importantly, lifecourse perspectives emphasize that such immune alterations should be more potent earlier in life during a sensitive period when bodily tissues are highly plastic to environmental inputs. However, examining these propositions is resource intensive, as they require cell-culturing approaches to model functional inflammatory activities, a wide age range, and longitudinal data. Here, we integrated data from five independent studies to create a diverse sample of 1,607 individuals (960 with longitudinal data; 8 to 64 years old; 359 Asian, 205 Black, and 151 Latino/a). Leveraging the resulting lifecourse data, rich interview assessments of disadvantage and stress, and ex vivo assessments of inflammation, we examined two questions: (1) Does chronic stress account for the link between disadvantage and proinflammatory phenotype? (2) Is there a developmental period during which inflammatory responses are more sensitive to disadvantage and chronic stress? Disadvantage was associated with higher chronic stress, which was linked with a proinflammatory phenotype cross-sectionally, longitudinally, and in terms of prospective change across 1.5 to 2 years. Consistent with the sensitive period hypothesis, the magnitude of these indirect associations was strongest in earlier decades and declined across the lifecourse. These findings highlight the importance of taking a lifecourse perspective in examining health disparities.