London: Men who smoke may see more of their Y chromosomes disappear as they age, a new study suggests.
Scientists have long known that as men grow older, the Y chromosome can start to disappear from some of their body cells. And that was initially thought to be a normal part of aging. The new study in Science, adds to those results: It found that older men who smoke typically lose more Y chromosomes from their blood cells than non-smokers do.
The finding hints at one possible explanation for why male smokers tend to face higher cancer risks than female smokers, according to Lars Forsberg, a researcher at Uppsala University in Sweden who led the study.
 There are smokers who don’t show a loss in the chromosome, and non-smokers who do, Forsberg noted — just as many smokers don’t developcancer, and many non-smokers do.
“But overall,” he said, “smoking is associated with loss of Y, and loss of Y is associated with cancer.”
Men have an X and a Y chromosome, while women have two X chromosomes. And experts used to think that the Y — short and stumpy compared with the X — did little more than determine male sex and ensure normal sperm production.
“The bottom two-thirds of the Y chromosome was seen as just repetitive DNA that doesn’t code for anything,” explained Dr. Martin Bialer, a medical geneticist at North Shore-LIJ Health System in Great Neck, N.Y.
“But now we’re starting to think it may have more roles than just determining sex — though that’s a pretty important one,” said Bialer, who was not involved in the study.
Recent research has shown that the Y chromosome actually contains a large number of genes. Their jobs are not fully understood yet, but a couple of those genes may help suppress tumors, according to Forsberg’s team.