Socioeconomic status (SES) is a fundamental cause of health inequalities.

Since the early 19^th century, the poor have lived in worse health and died younger than the wealthy. Even the eradication of diseases, such as typhoid fever and tuberculosis, has left health inequalities unchanged. Link and Phelan developed their theory of fundamental causes to explain the persistence of socioeconomic health disparities.

This essay from a Journal of Health and Social Behavior supplement presents key findings that support the fundamental causes theory. SES is a fundamental cause of health inequalities because it demonstrates four essential features: 1) SES influences multiple disease outcomes; 2) SES is tied to multiple risk factors for disease and death; 3) there is an association between SES and health because of a disparity in resources; and 4) new factors that perpetuate the association between SES and health are constantly emerging.

Key Findings:

• Improved knowledge and treatment for a specific condition (e.g., breast cancer) widens differences in outcomes between SES groups.
• In a study of two clinics providing diabetes care, the clinic serving higher SES patients provided better continuity of care and the higher SES patients were more knowledgeable about their condition and treatment.
• SES differences in mortality rates are more pronounced when the cause of death is preventable. A study found that racial disparities in survival rates were greater for more preventable forms of cancer.

This article explains Phelan and Link’s fundamental causes theory of health inequalities. Although advances in medical knowledge have been shown to increase health disparities, the authors advocate policies that advance knowledge while aiming to reduce inequalities.