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 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.
Sperm motility decreases more in older men
Compared to men aged 20 to 29 years old, 35-year-olds had less motile sperm. The subtle drop in sperm motility actually began around age 30 and progressed by about 1% each year after that.
"The motility does change with age, and that probably will translate into the likelihood that, as a group, older men are going to have a harder time to fertilise," said Dr Andrew Wyrobek of Lawrence Berkeley National Laboratory in California, who wasn't 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% of the sperm in semen samples were alive, whereas 65% 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% fewer sperm with normal morphology.
Dr Wyrobek told Reuters Health that the findings agree with his own assessment of age-related changes in the semen of California men.
Age doesn’t mean difficulty conceiving
"The total sperm produced and the amount of sperm per volume doesn’t change, and that's what we found. The biggest changes were the physiological parameters," Dr Wyrobek said.
Dr Wyrobek said that the results show a lot of variability in men's sperm health, and more advanced age doesn't 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 online in Fertility and Sterility, wrote that the findings will be useful to serve as a baseline for further studies of semen health in China.
(Reuters Health, August 2011)