Early origins of socioeconomic inequalities in chronic inflammation: Evaluating the contributions of low birth weight and short breastfeeding

The United States is characterized by persistent and widening social inequities in a wide range of adult health outcomes. A life course approach challenges us to consider if, and how, these inequities trace back to early life conditions, and chronic inflammation represents a potentially important mechanism through which early environments may have lasting effects on health in adulthood. Low birth weight (LBW) and shorter durations of breastfeeding both predict increased inflammation in adulthood, which is associated with increased risk for cardiovascular disease, metabolic syndrome, and all-cause mortality. Using data from a large representative sample of young adults in the US (National Longitudinal Study of Adolescent to Adult Health (Add Health)), we document the socioeconomic status (SES) gradient in chronic inflammation, as indicated by concentrations of C-reactive protein (CRP). Using a nested set of structural equation models and marginal standardization techniques, we investigate the extent to which this gradient is explained by patterns of LBW and breastfeeding in infancy. Findings reveal a particularly important role for breastfeeding duration: Based on model predictive margins, increasing breastfeeding duration to three or more months corresponds to a flattening of the SES gradient by 80%, and 83% when LBW is eliminated. This study expands current understandings of the consequential role of developmental environments for population health and for addressing health inequities in future generations.