Researchers find why smoking riskier for men than women

Men who smoke are over three times more likely than nonsmokers to lose their Y chromosomes, according to researchers who have previously shown that loss of the Y chromosome is linked to cancer.

The study, published Thursday in the U.S. journal Science, may help explain why smoking is a greater risk factor for males compared to females and, in the broader perspective, also why men in general have a shorter life expectancy.

Only men have the Y chromosome, which is important for sex determination and sperm production.

"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," said Lars Forsberg of Uppsala University in Sweden, who led the study, in a statement.

"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," said Forsberg.

The risk was dose dependent, meaning that loss of the Y chromosome was more common in heavy smokers compared to moderate smokers. Some men who quit smoking even appeared to regain their Y chromosomes.

"These results indicate that smoking can cause loss of the Y chromosome and that this process might be reversible," Forsberg said. "This discovery could be very persuasive for motivating smokers to quit."

How loss of the Y chromosome is connected with the development of cancer throughout the body is still not clear, the researchers said. One possibility is that immune cells in blood, that have lost their Y chromosome, have a reduced capacity to fight cancer cells.