Helena Nordenstedt presents the Global Health Framework, which can help you to understand how income is related to health. Basically, low income countries tend to have a lower life expectancy than countries in higher income levels.
She shows that minority groups within countries (in all income levels) generally have a lower life expectancy than the rest of the population, but as the countries get richer and healthier, the health of the minorities also improve.
She also shows that there is no minority group in middle income and high income countries that has a life expectancy lower than the average in poor countries.