Observers note the discrepancy shows that larger studies are needed, using standardized methods to count the squirming little subjects. That's why the emphasis now and in the future will be to standardize how we do semen analysis so we can have a long-ranging understanding of what's going on. Sokol tells WebMD that her findings show there may be regional differences in sperm quality. Her results were similar to what others found with Chinese men, but differ significantly from a French study. But overall, research shows that sperm density has changed very little in the last 50 years.
Physicians say anatomical defects and hormonal deficiencies are common causes of male infertility.
And hormonal deficiencies refer to a lack of testosterone or its chemical precursors. Shanti tells WebMD that medication can also affect sperm counts. Blood pressure medication and steroids, including some dietary supplements used by athletes, can affect sperm counts. And there's evidence that alcohol and tobacco use may have adverse effects as well. Additionally, the WHO criteria for sperm concentration has changed in recent years.