Guardian Unlimited | Special reports | Smoking and fat speed up ageing, say researchers

Guardian Unlimited | Special reports | Smoking and fat speed up ageing, say researchers
James Meikle, health correspondent
Tuesday June 14, 2005
The Guardian

Smoking and obesity accelerate people's biological ageing processes as well as shortening their lives, researchers suggested last night.

Tobacco and having too much fat speed up the rate of DNA damage so that being obese adds nearly nine years to a person's age, while smoking a pack of cigarettes a day for 40 years adds more than seven, according to Tim Spector of St Thomas's hospital, London.

"We have shown someone who smokes and is obese at 30 can look and feel like someone who is 40. If you tell a girl in her teens or her 20s that if she carries on smoking she could die at 75 instead of 80, it might not have much effect. But if you tell her she is going to look much older when she is still a young woman, that could make her consider giving up cigarettes and eat healthily."

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Professor Spector and colleagues in the US reported their findings in a research letter published online by the Lancet. They analysed telomeres, sections of DNA that cap the ends of chromosomes in cells and prevent damaging unions with other chromosomes. Every time a cell divides, and as people age, their telomeres get shorter.

Doctors have long warned of the dangers to longevity from smoking and obesity, but analysing the molecular consequences is a far newer science. "Obesity and cigarettes cause oxidative stress to increase and this cumulative damage over time causes the loss of the telomeres, which we believe is a marker of accelerative ageing and accounts for why these people get heart disease, diabetes, osteoarthritis and other age-related disease," said Prof Spector.

The investigators measured concentrations of a body fat regulator, leptin, and telomere length in blood samples from 1,122 women between 18 and 76. Telomere length decreased steadily with age, and telomeres of obese women and smokers were much shorter than those of lean women and those who had never smoked.

Prof Spector said: "The difference in telomere length between being lean and being obese corresponds to 8.8 years of ageing, smoking (previous or current) corresponds on average to 4.6 years of ageing, and smoking a pack per day for four years corresponds to 7.4 years of ageing."

But ex-smokers had less shortening of their telomeres than those who still smoked. "Their rate of loss slows down. There is a point in giving up."

Despite these average trends, there was still variability between individuals, he said. It could be that people are born with a genetic susceptibility. Further work was under way to establish whether those with shorter telomeres had more arthritis, heart disease and hormonal problems, for instance with ovarian function.

There was not enough information at present for screening tests, he said, and for the moment the picture gave averages, rather than focusing on individuals.

However, he could see tests being developed in the future. "I am not sure everyone would necessarily want to know what they have been doing to themselves."

Lorna Layward, the research director of Help the Aged, said people already knew about the dangers of smoking and obesity. "While the [new] research is not conclusive, we should take heed of the alarm bells. Most over-65s are not getting enough exercise, which has massive implications aside from obesity, such as declining strength and mobility. Giving up smoking is the biggest thing you can do to reduce your chances of developing coronary heart disease."