A new study has found a link between smoking in men and Y chromosome loss - a mutation that has been shown previously to cause cancer. Because men are the only ones with a Y chromosome, the research could also help us to understand why ageing men - smokers or not - are affected by and die from most known types of cancer at a much higher rate than women.
When you smoke, you're not just putting yourself at risk of developing lung cancer, especially if you're a male. Statistics have shown that male smokers are more likely to develop other forms of cancer elsewhere in the body than female smokers, and a new study has suggested that this has to do with the way smoking affects the Y chromosome - a complex of DNA and tiny molecules that influence sex determination and sperm production in men.
Having analysed data related to 6,000 male volunteers, an international research team led by Lars Forsberg from the Department of Immunology, Genetics and Pathology at Uppsala University in Sweden has found that if you're a heavy smoker, you're likely experiencing Y chromosome loss.
"We have previously in 2014 demonstrated an association between loss of the Y chromosome in blood and greater risk for cancer," Forsberg says in a press release. "We now tested if there were any lifestyle or clinical factors that could be linked to loss of the Y chromosome. 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."
Other factors tested for included exercise habits, cholesterol levels, and education status.
The team found that this genetic damage was related to how much a person smokes - if you're a moderate smoker, you'll lose less Y chromosomes than a heavy smoker - and if you quit, you're likely to regain the same levels as non-smokers in your cells.
"These results indicate that smoking can cause loss of the Y chromosome and that this process might be reversible," says Forsberg. "This discovery could be very persuasive for motivating smokers to quit."
Publishing in the journal Science today, the researchers say they've been able to show that Y chromosome loss is induced by smoking, and is then linked to a higher risk of developing cancer, but at this stage, they're not sure why.
Y chromosome loss doesn't just occur when men smoke, it can also occur as part of the ageing process. According to Pippa Stephens at BBC News, in a previous study, the team analysed data from 1,153 elderly men in Sweden to discover that "those who had lost part of their Y chromosome died on average 5.5 years earlier than those who had not". They suggested that this could somehow be linked to the fact that, on average, women in Europe live 7.5 years longer than men.
So far, no one's been able to explain why men, in general, have shorter lifespans than women, and experience higher rates of cancer. One possibility, the team suggests, is that immune cells in the blood could be adversely affected by age-related Y chromosome loss in a way that weakens their response to cancer cells.
According to Arielle Duhaime-Ross at The Verge, the team will now try to identify which blood cells are the ones that are losing their Y chromosomes, and then use that information to help them figure out exactly why Y chromosome loss is linked to shorter life expectancies and an increased risk of developing cancer. But even before those results come out, Forsberg already has a pretty strong opinion on the matter of smoking. "If you want to stay healthy and alive," he told Duhaime-Ross, "quit smoking today."