Men who smoke are more likely than non-smokers to lose the male sex chromosome – which could explain why male smokers are more prone to certain cancers than women who smoke, scientists have said.

Researchers found that male smokers had significantly fewer blood cells with a Y chromosome compared to non-smokers, and that the trend increased with heavy smoking – and disappeared when a man gave up cigarettes.

“We have previously 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,” said Lars Forsberg of Uppsala University in Sweden, who led the study published in the journal Science.

“Out of a large number of factors that were studied, such as age, blood pressure, diabetes, alcohol intake and smoking, we found that loss of the Y chromosome in a fraction of the blood cells was more common in smokers than in non-smokers,” Dr Forsberg said.

The risk was dose dependent, indicating that the more cigarettes a man smoked, the greater the proportion of blood cells with missing Y chromosomes. Giving up cigarettes led to a reversal of the mutation, Dr Forsberg said.

“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. This discovery could be very persuasive for motivating smokers to quit,” he said.

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