Smoking may turn out to be a bigger enemy to men than anyone ever imagined. New research published in the journal Science shows that smoking cigarettes can “delete” the Y chromosome – the male sex chromosome that is responsible for determining sex. The discovery was made after long-term monitoring of three groups of men over the age of 48. A comparison of DNA from blood samples clearly shows that smokers have lost many more Y chromosomes than non-smokers. Other factors were also tested, such as sports, diabetes, body mass index, education, alcohol use and others, but a significant increase in Y chromosome loss was observed only in smoking. NEWS_MORE_BOX The authors note that, at present, this is the most common nonzygous mutation. It occurs in 12-16% of samples in people over 70 years old. Loss is 2.4 to 4.3 times more likely in smokers. Loss of this type of chromosomes does not affect reproductive abilities, but is often observed in patients with advanced stages of cancer. In men, a low number of Y chromosomes is also associated with a shorter life expectancy and higher risks of cancer. Scientists are not yet sure what the link between chromosome loss and cancers is, but the most likely explanation is the frequency of mutations and DNA copying errors.