A new study of age-related changes in semen in Chinese men shows sperm health can start declining as early as age 30, with notable changes after age 35, although the research stops short of determining the effects on fertility.
Dr. Qian-Xi Zhu and colleagues at the Shanghai Institute of Planned Parenthood Research looked only at physical and activity changes in the sperm, and found marked declines in both.
Sperm numbers and semen volume remained more constant with age.
About 1,000 men from age 20 to 60 donated sperm for analyses of how much semen they produced, the number of sperm in their semen, how well those sperm moved and whether they appeared normal.
Compared to men aged 20 to 29 years old, 35-year-olds had fewer sperm able to propel themselves -- a behavior important for fertilization. The subtle drop in sperm "motility" actually began around age 30 and progressed by about one percent each year after that.
"The motility -- the ability of the sperm to move -- does change with age, and that probably will translate into a likelihood that, as a group, older men are going to have a harder time to fertilize," said Andrew Wyrobek, a sperm specialist at Lawrence Berkeley National Laboratory in California, who was not involved in this research.
The percentage of sperm alive in each semen sample was also lower among older men. In 20- to 29-year-old men, for instance, 73 percent of the sperm in semen samples were alive, whereas 65 percent of sperm in samples from 50- to 60-year-olds were alive.
After age 30, the number of normal-looking sperm also began to fall. Compared to men in their 20s, those in their 50s had 16 percent fewer sperm that appeared normal.
Wyrobek told Reuters Health that the findings agree with his own assessment of age-related changes in the semen of California men.
"The total sperm produced and the amount of sperm per volume pretty much don't change, and that's what we found. The biggest change were the physiological parameters," Wyrobek said.
Wyrobek said that the results show a lot of variability in men's sperm health, and older age does not necessarily mean a man will have difficulty conceiving.
He added that the genetic quality of the sperm as men age is a totally different question, and one that was not addressed here.
The authors of the study, which was published in the journal Fertility and Sterility, wrote that the findings will be useful to serve as a baseline for further studies of semen health in China.