Smoking is widely recognized as one of the biggest risk factors for cancer. A new study has now demonstrated that smoking is associated with the loss of the Y chromosome in blood cells, potentially explaining why smoking is more of a risk factor for cancer among men.

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Smoking was found to have an association with the loss of the Y chromosome in male smokers, which was affected by the frequency of smoking.

Only men have the Y chromosome, which “may in part explain why men in general have a shorter life span than women, and why smoking is more dangerous for men,” says lead researcher Prof. Jan Dumanski, of Uppsala University in Sweden.

Researchers have already shown that male smokers are more likely to develop cancer outside of the respiratory tract than female smokers. In the new study, the discovery of a potential link between smoking and genetic damage that only affects men could account for this difference.

‘We have previously in 2014 demonstrated an association between loss of the Y chromosome in blood and greater risk for cancer. We now tested if there were any lifestyle or clinical factors that could be linked to loss of the Y chromosome,” explains Lars Forsberg, another of the researchers.

Most people have 46 chromosomes in their cells, and two of these are sex chromosomes. Females have two X chromosomes, whereas males have one X and one Y. It is believed that the Y chromosome contains around 50-60 genes that provide the body with instructions for creating protein.

Certain health conditions are related to changes in particular genes within chromosomes. For example, Y chromosome infertility – a condition affecting the production of sperm – is caused by the deletion of genetic material in regions of the Y chromosome.

In the team’s previous work, Forsberg and his colleagues found that men who lost the Y chromosome in large amounts of their blood cells had a lower survival rate. Correlation was also observed between the loss of the Y chromosome and the risk of dying from cancer.

“Our results indicate that the Y chromosome has a role in tumor suppression, and they might explain why men get cancer more often than women,” said Prof. Dumanski, regarding the previous study published in Nature Genetics.

For their new study, published in Science, the researchers assessed a large number of factors, such as age, alcohol intake, blood pressure, diabetes and smoking, to see if any could be associated with males losing the Y chromosome.

They found an association between smoking and Y chromosome loss that was dose-dependent; participants who smoked heavily were more likely to experience Y chromosome loss than moderate smokers. The association was also only observed in current smokers; men who had quit smoking experienced the same level of Y chromosome loss as men who had never smoked.

Forsberg says their findings could help persuade smokers to quit their habit:

These results indicate that smoking can cause loss of the Y chromosome and that this process might be reversible. We found that the frequency of cells with loss of the Y chromosome was not different among ex-smokers compared to men who had never smoked.”

The researchers are yet to establish the reason why the loss of the Y chromosome in blood cells is connected to the development of cancer throughout the body. One theory is that Y chromosome loss could impair the capacity of white blood cells to fight cancerous cells.

Further exploration of this association could lead to additional discoveries in the study of cancer. For the time being, it may serve as one more reason for people to try and quit one of the most harmful habits around.

Elsewhere, researchers recently identified a series of changes in the brain that occur when someone quits smoking. The team believes that these changes may help predict which individuals begin smoking again in the future.