In Australia, the life expectancy gap is four years for males and two years for females between the highest and lowest socio-economic groups. In America, there is a ten year life expectancy gap between the highest and lowest socio-economic groups.

Why do people in higher socio-economic groups live longer? Lots of reasons. Access to health care is one reason.

A new study published in November 2016 in the journal Science suggests that part of the reason may be that a higher socio-economic status also boosts immunity from diseases.

For the study, researchers gathered 45 unrelated captive macaque monkeys, that had never met each other, and put them together. The researchers observed how the monkeys related to each other and who was dominant and who was submissive. The monkeys sorted themselves into hierarchical orders based on seniority – those who arrived in the group first were considered to be higher ranked.

The researchers (and monkeys) were from the Yerkes National Primate Research Center of Emory University. The researchers also included Noah Snyder-Mackler, postdoctoral researcher at Duke University, Jenny Tung, assistant professor of evolutionary anthropology and biology at Duke University, and Luis Barreiro, assistant professor of immunogenomics at the University of Montreal in Canada.

Taking immune cells from the monkeys, the researchers measured the activity of 9,000 genes and found that 1,600 of them were different in the lower-ranking monkeys, notably in cells called natural killer cells that are the first line against infection.

Then the researchers rearranged the monkeys into nine new social groups. Again, the macaque monkeys sorted themselves in order of arrival with the first monkeys to join the new groups ranking higher than late comers. This meant that monkeys previously low on the ladder moved up the ladder and also vice versa.

Taking the immune cells from the monkeys again, the researchers found that the immune cells of previously low-ranking monkeys became more like high-ranking monkeys in terms of which genes were turned on and off. In other words, their immune systems improved when their rankings in their social group improved.

If similar molecular mechanisms underlie the link between social status and health in humans, interventions that improve a person’s social support network could be just as important as drugs for mitigating the physiological costs of low status, said the researchers at Emory University.

The encouraging outcome is that the effects of socio-economic status aren’t permanent. For example, the immune system of a person with a low socio-economic status is also low, but it does not stay low when moving up the socio-economic ladder. A rising socio-economic status lifts immunity. And an improved immune system results in better health and a longer life.

There is a saying: a rising tide lifts all boats. If society can raise the living standards of all people then the health of society in general will improve for everyone.

“Social Status Alters Immune Regulation and Response to Infection in Macaques,” Noah Snyder-Mackler, et al. Science, Nov. 25, 2016. DOI: 10.1126/science.aah3580.

Photograph: John Cleese, Ronnie Barker, and Ronnie Corbett