The study, published Thursday, Feb. 6, in the journal Human Reproduction, suggests that even healthy men may become progressively less fertile as time goes by.
"Prior studies on semen quality typically included men who came to fertility clinics," said Brenda Eskenazi, professor of epidemiology and maternal and child health at UC Berkeley's School of Public Health, and co-author of the study. "This is one of the first studies to focus on men with no known fertility concerns, giving us a better sense of whether age affects semen quality in a healthy population."
The researchers recruited 97 men between the ages of 22 and 80 who were employed or retired from Lawrence Livermore National Laboratory. Samples were brought to the onsite research laboratory within two hours after collection to accurately measure sperm motility - its liveliness and direction of movement - and other indicators of semen quality. The researchers gathered extensive medical, lifestyle and occupational exposure history from the men, and excluded those who had smoked in the prior six months or had other relevant health problems.
While age had an effect on semen volume, the more significant impact was on sperm motility, which researchers found decreased by 0.7 percent per year. That means the chance of sperm motility being clinically abnormal is 25 percent at age 22, 40 percent by age 30, 60 percent by age 40 and 85 percent by age 60.
"Simply put, sperm slow down with age," said study co-author Andrew Wyrobek, head of the Health Effects Genetics Division at Lawrence Livermore National Laboratory. "In addition, age impacts progressive motility, which is the ability of sperm
Contact: Sarah Yang
University of California - Berkeley