Every sperm is sacred, but older ones need even more TLC than previously thought. Although scientists have long theorized that sperm quality drops as men age, a University of Otago review of 90 studies from more than 30 countries confirms there are "consistent age-related declines" in the quantity of semen, the health of sperm, and sperm's ability to perform, Science Daily reports. The results, published in Ageing Research Reviews, could help fertility researchers dealing with couples delaying pregnancy until later years and anticipating problems with resulting offspring. "While female age is well known to have negative effects on fertility, reproductive success, and the health of offspring, the influence of male age on a couple's fertility has been largely neglected," says Sheri Johnson, the article's lead author.
Although the review doesn't say at what age sperm starts declining, Johnson mentions that certain "well-controlled" studies have found consistent deterioration for certain sperm traits after men turn 35 or 40. The authors say it's important to consider aging sperm to prevent unnecessary IVF treatments—it could be the man's issue, not the woman's, that's preventing pregnancy—and to better assess risk for birth complications, miscarriage, and child disorders such as Down syndrome, autism, and schizophrenia. What's more, they say, experts should start evaluating sperm by its health and ability perform rather than using older measures like semen quantity, sperm concentration, and sperm count. (Macho guys might not have great sperm, either.)