Infertility isn’t just a woman’s problem. Four in 10 cases are linked to the male partner, estimates the American Society for Reproductive Medicine. Often the cause is physical. (A swelling of the veins that drain the testicles can lower sperm quality, for example.) But lifestyle factors may play a role, too.
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As men get older, the volume of their semen may decrease, and the percentage of chromosomally normal sperm may also drop.
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Men with waistlines of 40 inches or more have about a 22 percent lower sperm count than men with waists under 37 inches, per a 2014 study.
Research performed at Harvard found that guys who consume a diet high in saturated fat have lower sperm counts.
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Excessive alcohol use has been linked to lower sperm production, erectile dysfunction and decreased testosterone.