In Sickness and in Wealth Directed by Llewellyn M Smith (2008) Film Review It’s no mystery and doesn’t need yet more study. Epidemiologists have known since the late seventies that health and life expectancy directly correlate with income level, irrespective of genetics, lifestyle (smoking, exercise, diet, etc), or access to medical care.
The study reinforced prior research* indicating that neither genetics, lifestyle, nor access to medical care has as much influence on health outcomes as income and social status.
Scientists believe low social status leads to poorer immune function and adverse health effects due to the total lack of control poor people have over their lives. This absence of control tends to result in high chronic stress levels that contribute directly to high blood pressure, heart disease, obesity, and impaired immunity.
Overall African Americans had worse health outcomes than white residents regardless of income or social status. Scientists believe this relates to the chronic stress they experience related to racial slights and abuse in their interactions with white people.