Research suggest that social class determines how quickly the body ages, without respect to factors like diet, bad habits and health.

A groundbreaking study of twins led by British researchers has shown that people of lower socioeconomic standing, whether due to their jobs or the person they marry, age seven years faster than their more fortunate peers.

Poorer health, bad habits and less pampering may have long been thought to play a role in shorter life spans for Britain’s blue-collar workers, but now biological mechanisms have been identified as well.

The study involved over 1,500 women and shows a dramatic and inexplicable association between social status and the rate of the body’s deterioration.

Professor Tim Spector of St. Thomas’ Hospital in London said the effect could not be explained solely by low income status, poor education or health risk factors common to those lower in the socioeconomic scale – such as smoking, obesity, poor exercise habits and bad diet.

Professor Spector, who works in St. Thomas’ twin research and genetic epidemiology unit, said that stress may be the key here. People from lower social backgrounds are more likely to feel insecure, especially at work, and suffer low self-esteem and a sense of lacking control of their lives, he said. The stress this causes is believed to inflict damage at a cellular level, thus accelerating aging.

The study findings are to be published in the journal Aging Cell, and are the latest to emerge from the hospital’s twin unit, which is engaged in ongoing studies of twins to show how people are affected by genes or their environment.

Spector and colleagues, some in the US, recruited a group of 1,552 British women aged 18-75 (identical and fraternal twins) for the study. Subjects were assigned to one of 5 officially recognized socioeconomic groups. The scientists then examined their chromosomes. The DNA bundles have protective caps that act like the ends of shoelaces to prevent them from fraying and becoming damaged. The caps, called telomeres, can be likened to time-delay fuses. When a cell divides, they shorten, until a point is reached where the chromosome can longer be kept stable. The cell then ceases to divide and it may die.

Experts believe telomere shortening is a marker for aging. Spector found a striking difference in the length of telomeres between those from working-class and white-collar backgrounds.

Women of the same age were categorized as having manual or non-manual jobs, and the rate at which their telomeres shortened each year was measured. Those from the manual group had telomere “fuses” that were approximately 7 years shorter on average.

Biologically speaking, they were seven years “older” than the non-manual group subjects, despite being the same chronological age. “We’re talking about a seven-year difference in telomere loss between people of the same age, the same body mass index, and the same smoking and exercise status, who happen to be in a manual or non-manual job,” Professor Spector said. “A seven-year difference is obviously a large one.”

Spector added that risk factors alone did not explain more than a third of the lifespan disparity between the social classes.

The researchers went on to compare the telomere lengths of 17 twin pairs who started life in the same social category but then separated, with one moving up the scale and one moving down. Generally, this was the result of the women marrying.

In 12 cases, relocating to a new socioeconomic group had an even larger impact on telomere shortening that equaled nine years for women of an average age of 47. Spector said, “We’re a social species. I don’t think we’ll ever be in a socialist utopia where everyone is equal and has the same level of stress.”

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