Socio-economic influences from egg to exit: Emerging biology.

Socio-economic status (SES) impacts life-long health from early development to old age. We review SES differences in biological factors that begin before fertilization and extend into later life, 'egg to exit'. SES gradients are shown in onset and prevalence of chronic conditions including cardiovascular disease, diabetes and dementia, leading up to a 15-year difference in life expectancy in some countries. Our analysis is limited to high-income countries and does not include detailed discussion of gender or ethnic differences. We develop a comprehensive multi-disciplinary framework for SES gradients in health and aging extending from the population level to gene expression. This framework integrates biological processes such as developmental programming and epigenetic regulation into a unified life-course model. Key components in the ´SES exposome´ are diet, cigarette smoke, environmental and household air pollution, and psychosocial stress. Interactions between psychosocial stress, diet and environmental pollution are incompletely understood. Inflammation and oxidative damage occur in in many organs. Some mechanisms are experimentally testable in cells and rodents, but these models cannot evaluate human aging for psychosocial factors and multi-generational interactions. SES influences are modified by social mobility ('SES fluidity'), yet some biological changes, such as DNA mutations and collagen cross-linking, have limited reversibility. This integrative analysis provides a framework for future research and potential remediation of SES constraints on health and aging.