AS if being bottom of the social pile isn鈥檛 bad enough, it now seems that it also makes the body鈥檚 cells age prematurely.
People from lower socio-economic groups are more likely to die earlier than people in non-manual jobs from heart attacks, strokes and cancer. Unhealthy habits such as lack of exercise, excess weight, smoking and poor diet account for around a third of these deaths.
Now, a study on white blood cells from 1552 female twins suggests that cells from women with more menial jobs age faster, even after taking these factors into account. On average, their cells were seven years 鈥渙lder鈥� than those from women of the same chronological age with non-manual jobs.
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To estimate cell ageing, Tim Spector of St Thomas鈥� Hospital in London and his colleagues measured the lengths of telomeres, the repeating DNA motifs that cap and protect the ends of chromosomes. Telomeres grow shorter each time a cell divides, so the shorter the telomeres in a cell, the more times it has divided, and the more stress it is likely to have been under.
They found that telomeres were on average 140 DNA base pairs shorter in manual workers than in non-manual workers of the same age. Since around 20 base pairs of telomere DNA are lost on average each year, this makes the cells from the manual workers about seven years older.
In 17 pairs of twin sisters who married men at opposite ends of the social scale, their telomeres showed an average age difference of nine years, despite the women being genetically very similar (Ageing Cell, DOI: 10.1111/j.1474-9726.2006.00222.x).
Spector suggests that low status might drive cellular ageing because such people are under greater psychological stress. This could have subtle metabolic effects, exposing their cells to more oxidative damage, he says.
鈥淭he greater psychological stress of being in a low social class, with more people above you in the food chain and less control over your life, is the unseen hand that might mean more stress at cellular level,鈥� he says. 鈥淥xidative stress does make telomeres shorten.鈥� He expects to see the same effect in men.
