The study looked at the semen quality of 16,835 infertile men in China compared to 1,567 sperm donors. They found that infertile men had higher rates of asthenospermia (weak sperm movement) compared to the control group. Azoospermia, asthenospermia, and oligoasthenospermia were linked to infertility, while simply having low sperm count (oligozoospermia) was not always related to infertility.