The early origins of socioeconomic inequalities in inflammation: a scoping review and recommendations for life course and longitudinal studies.

Inflammation is a key mechanism underpinning socioeconomic inequalities in health. In adults, lower socioeconomic position (SEP) is associated with higher inflammation levels. Early life is an important period for the biological embedding of the social environment, with implications for life course health trajectories. There is therefore increasing interest in the relationship between SEP and inflammation in children and adolescents. We conducted a scoping review to summarise and critically appraise existing evidence. Studies were included if they had exposures of any SEP indicator and outcomes of any inflammatory biomarker. Community and population studies were considered. Twenty-seven of 41 studies identified showed that lower SEP was associated with higher inflammation in childhood or adolescence. Associations were most evident in high-income countries. However, interpretation and translation of findings were restricted by a limited range of SEP indicators and inflammatory biomarkers, and inconsistent or arbitrary timing of exposures and outcomes. Drawing from this review, we make five recommendations for future work in this important domain. We suggest that future studies endeavour to: (1) measure structural and social conditions more comprehensively across early life; (2) use a broader range of inflammatory biomarkers and related measures; (3) investigate effects on long-term immune phenotype; (4) expand study settings globally and across more diverse population groups; and (5) leverage multidisciplinary teams of social and biological scientists to triangulate evidence. Implementation of these recommendations may facilitate an expansion of evidence that better informs specific and timely interventions to address the root causes of socioeconomic inequalities in health.