Scientists have uncovered evidence of a new class divide: the lower our social standing, the faster we age.
The claim follows the surprise discovery of accelerated ageing among working class volunteers, leaving them biologically older than those higher up the social ladder.
Genetic tests showed that being working class could add the equivalent of seven years to a person's age.
And moving down in the world by marrying someone from a lower social class also added years to a woman's biological age, scientists report today in the journal Aging Cell.
The researchers, lead by Professor Tim Spector at St Thomas' Hospital in London, ruled out differences in income, smoking, bodyweight and exercise, and believe instead that being at the bottom of the social pile breeds insecurity and low self-esteem. This triggers high levels of stress which may increase damage on the cellular level and speed up the natural ageing process, the scientists say.
The finding may explain the large difference in death rates between different social classes, not all of which can be explained by poorer lifestyles. "Not only is social class affecting health and age-related diseases, it seems to have an impact on ageing itself", Prof Spector said.
The study is the latest to emerge from Prof Spector's Twin Research and Genetic Epidemiology Unit which aims to tease apart the effects that genetics and environment have on people.
The team recruited 1552 British women, all of whom were twins aged 18 to 75, and assigned them to one of five officially-recognised socio-economic groups. The scientists then took blood samples and used genetic tests to look at chromosomes in their white blood cells.
The scientists looked at caps on the ends of chromosomes, called telomeres, which protect them from damage. Each time a cell divides, the telomeres shorten like fuses, until the cell eventually dies.
When the scientists divided the women into manual and non-manual workers - a split that roughly grouped them into working class and middle class - they found that the manual workers had much shorter telomeres, equivalent to being an average of seven years older. Factors such as bodyweight and lifestyle were taken into account.
"A seven year difference is obviously a large one. It equates with the epidemiological data showing that if you look at death rates of different classes of people, those in social class four and five die several years before those in one and two", said Prof Spector.
The scientists went on to compare the telomere lengths of 17 twin pairs who started life on the same social rung but then split, with one moving up the scale and the other down. Often, this was governed by whoever the woman married.
In 12 cases, changing socio-economic group had an even bigger impact on telomere shortening - the equivalent of nine years for women with an average age of 47.
The discovery suggests that class, and the stress levels associated with social standing, have a constant influence on the rate at which we age.
"I don't think we'll ever be in a social utopia where everyone is equal and has the same levels of stress, but there is an unmet issue here in the psychological wellbeing of the poorest people in the society. The more people are in control of their lives, the better", said Prof Spector.