Smoking not only causes about 90 per cent of all lung cancer deaths, but can also expedite the ageing process, according to a study of nearly 500,000 people which was presented at the European Respiratory Society International Congress in Milan, Italy recently.
It showed that smoking shortens the end fragments of chromosomes in the white blood cells of our immune systems. “The length of these end fragments, called telomeres, is an indicator of how quickly we age and our cells’ ability to repair and regenerate. “Our study shows that smoking status and cigarette quantity can result in the shortening of leukocyte telomere length, which is an indicator of tissue self-repair, regeneration and ageing.
In other words, smoking can accelerate the process of ageing, while quitting may considerably decrease the related risk,” said Siyu Dai, Assistant Professor in the School of Clinical Medicine at Hangzhou Normal University in China. Telomeres are lengths of repetitive DNA sequences that protect the ends of chromosomes. “Each time a cell divides, the telomeres become slightly shorter, eventually becoming so short that the cell can no longer divide successfully, and it dies.
This is part of the ageing process. “Telomere length in white blood cells (called leukocytes) has been linked previously to smoking, but, until now, there has been little research into whether smoking status and the quantity of cigarettes smoked actually caused the shortening in telomere length,” said Dai.
The researchers used genomic data from 472,174 UK Biobank participants, related to current smokers, those who never smoked, and for people who had smoked previously. They found that current smoking status was statistically significantly associated with shorter leukocyte telomere length, whereas previous smokers and people who had never smoked didn’t show significantly shorter leukocyte telomere length.
Among people who used to smoke, there was a trend towards shorter telomere length, but this was not statistically significant. People who smoked the greater number of cigarettes had significantly shorter leukocyte telomere length.
“In summary, smoking may cause shortening of leukocyte telomere length, and more cigarettes smoked, the stronger the shortening effect,” said Dai.