(LIVESCIENCE) — Add another troubling side effect to the list of health issues caused by cigarettes: Smoking may cause the Y chromosome to disappear from men’s blood cells.

A new study finds that men who smoke lose the Y chromosome in blood cells more frequently than nonsmokers — and the heavier their cigarette use is, the fewer Y chromosomes they have.

This Y chromosome loss could explain why male smokers are at higher risk of cancer than female smokers, the researchers said in their study, published today (Dec. 4) in the journal Science.

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