Time Magazine has a report on several new studies that indicates men experience a loss of fertility as they age -- just like women do -- and that older paternal age is associated with risks such as bipolar disorder. This of course flies in the face of common attitudes towards fertility that see infertility primarily as a woman's problem. Apparently as much as a 50% of infertility may be due to men, not women:

Not only do men become less fecund as they age, but their fertility begins to decline relatively early — around age 24, six years or so before women's. Historically, infertility has been seen as a female issue, as has the increased risk of Down syndrome and other birth defects, but studies now also link higher rates of autism, schizophrenia and Down syndrome in children born to older fathers. A recent paper by researchers at Sweden's Karolinska Institute found that the risk of bipolar disorder in children increased with paternal age, particularly in children born to men age 55 or older.

It used to be that "if you had hair on your chest, it was your wife's problem," says Barry Behr, an associate professor of obstetrics and gynecology at the Stanford Medical School and director of Stanford's in vitro fertilization laboratory. Even now, he said, though about half of infertility cases are caused by male factors, such as low sperm count or motility, there are many more tests to evaluate a woman's fertility than a man's.

You can find the Swedish study on bipolar disorder here, and the French study on age and pregnancy rates here.

And PS: isn't that photo of a microscope sold in Japan AMAZING? Thanks to Gizmodo for that. Notice not just the happy sperm, but also the DEAD sperm on the box. How amazing!