Chinese student donors could be a reference population when monitoring sperm quality

decades (20–50 years) and concerning thousands of individuals.3 Although interesting and alarming, observed changes during a 4-year observation of 1808 men do not allow a formal conclusion, especially as confounding factors such as tobacco, alcohol consumption or body mass index were not considered. Authors suggested that environmental, psychosocial and climate factors may explain the non optimal sperm quality of the analyzed population. As described in Table 5, semen quality differences were previously observed between different European countries.4 Changes in sperm parameters were also observed across seasons in Europe,4 but, despite huge climatic variations in Wuhan city, semen quality did not dramatically vary in Rao’s study.1 Although not without limitations, this study has the merit to describe with rigorous methods the sperm parameters of a homogeneous population that is exposed to detrimental environmental factors. Being complex and fragile, human reproductive function can be considered as a “sentinel function,” witness to the health impact of environment or behavior changes.5 That way, sperm quality could be a health marker and student sperm donors could constitute a reference population that should be monitored in the coming years.