Here's an example: In a study in Germany, researchers examined a national database that contained the data from all (5 million) retired German men over the age of 65 (as of 2003). What they looked for was data on deaths grouped by lifetime income, type of work and other variables. They grouped the men into five groups based on their income level. They showed that mortality for retired German men varies by 60% with life expectancy at age 65 ranging from 14.9 to 18.5 years. Former manual workers had a 35% higher risk of death than salaried workers (and those on public insurance had a 44% greater chance than those using private insurance). In the end, a retired manual worker on public insurance in the lowest income group is 3 times more likely die than a wealthier, privately insured former salaried worker.
Why?
Good question. No one knows for sure. There are two dominate theories. The first is simple: It states that people with more wealth have more resources available to secure good medical care. This certainly explains some of the findings (such as the health insurance effect), but there is still some explaining to be done.
In the UK, a famous study called the "Whitehall Study" which examined government workers (all of whom had the same type of health care), found that the higher someone was in the hierarchy, the longer they lived. Recently, another study also showed the Nobel prize winners simply liver almost 2 years longer than people who were nominated, but did not receive a Nobel. This leads to the second theory, we'll call it the "Hierarchy Effect," which states that being lower in the social hierarchy independently impacts health through increases in the release of stress hormones. This has been shown fairly well in animal studies where researchers monitor the levels of stress hormones in primates and have found that being nearer the top reduces the overall level of stress hormones (but note that being at the top actually increases them because the top chimp must continually defend his position).
Sources:
Marmot MG, Smith GD, Stansfeld S, Patel C, North F, Head J, White I, Brunner E, Feeney A. Health inequalities among British civil servants: the Whitehall II study. The Lancet 1991; 337:1397-93.
Shkolnikov VM, Scholz R, Jdanov DA, Stegmann M, von Gaudecker HM. Length of life and the pensions of five million retired German men. Eur J Public Health. 2007 Nov 5.
Matthew D. Rablen and Andrew J. Oswald. Mortality and Immortality. The Warwick Economics Research Paper Series (TWERPS) from University of Warwick, Department of Economics.
