Background: In many places, income and income inequality are studied as factors that influence people’s health. Many of the theories that associate income with health outcomes analyze the individual, the environment, and how income influences health, but not the effects of income on health. Main text: We present a new theory that explains how income change influences people’s health. We have based the example of breast cancer mortality and per capita income in Brazil, where the emerging socioeconomic development makes it a developing country with characteristics of developed countries. For this, we used two databases consolidated in scientific research: the atlas for human development in Brazil made available on the basis of the United Nations Development Program and the National Cancer Institute’s base on cancer mortality in Brazil. Age-standardized breast cancer Mortality and per capita income in Brazilian rears was collected. Annual Percentual Change was used to estimate the variation in the period and Simple Linear Regression to estimate the relationship between mortality and mortality and the variation of mortality with income variation. The confidence level was 5%. The program used was Stata ® (StataCorp. LLC) 11.0. Conclusion: We find that change in income influences mortality differently, proving our theory. More studies are needed to better develop and understand this relationship.