DHAKA: Simply being at the bottom of the social heap directly alters the body in ways that can damage health, a study at Duke University in the US suggests.
Monkey experiments showed low status alters the immune system in a way that raises the risk of heart disease, diabetes and mental health problems.
One expert said the findings were “terrifically applicable” to people.
The findings, in Science, had nothing to do with the unhealthy behaviors that are more common in poorer groups.
The gulf in life expectancy between the richest and poorest is huge - in the US it is more than a decade for women and 15 years for men.
Part of the explanation is that people from poorer backgrounds are more likely to have a worse lifestyle - including smoking, little exercise and diets containing junk food.
But the latest study goes further to show low status - with all of those other factors stripped out - still has an impact on the body.
Looking at 45 non-human primates allowed scientists to adjust only social status to assess its impact - something impossible to do in people.
The captive Rhesus monkeys - who were all female, unrelated and had never met before - were divided one-by-one into nine new groups of five.
The newest member nearly always ended up at the bottom of the social order and became “chronically stressed”, received less grooming and more harassment from the other monkeys.
It had the impact of making the immune system run too aggressively in those at the bottom. High levels of inflammation cause collateral damage to the body to increase the risk of other diseases.
One of the researchers, Dr Noah Snyder-Mackler, told the BBC News website: “It suggests there is something else, not just the behaviors of these individuals, that is leading to poor health.
Sir Michael Marmot, one of the world’s leading experts on health inequalities and based at University College London, said the findings were “extraordinarily interesting” and underpinned much of his own research.
He told the BBC News website: “This is hard science saying there is a plausible biological mechanism that results in clear differences depending where you are in the hierarchy.”
“The gateway through which the social environment impacts health is the mind. Whether it is unhealthy behaviors or direct stress, the mind is crucial and this study is lending real credence to that.”
While Rhesus macaques do form strict societies, they are far more simplistic that human ones.
But Prof Graham Rook, from University College London, told the BBC News website: “All the evidence is showing the findings are terrifically applicable to humans.”
He pointed to evidence suggesting people at the bottom end up with worse health when the top gets richer, even if they themselves do not get any poorer.
Hierarchies are a fixture of society. However, the researchers believe more can be done to ease the health problems coming from being bottom of the pile.
BDST: 2040 HRS, NOV 27, 2016