Sperm count and motility are declining, an 11-year longitudinal study of sperm donors in the United States shows.
"Our study suggests that there is a time-related decline in semen quality, which could be a reflection of many different changes in our environment and lifestyle," said Sydney Chang, MD, from the Icahn School of Medicine at Mount Sinai in New York City.
Although sperm counts were not at a level that would have an impact on fertility, "it is an important finding that warrants further investigation," she said at the American Society for Reproductive Medicine 2018 Scientific Congress in Denver.
Chang and her colleagues analyzed sperm count, sperm concentration, and motile sperm count in samples from donors 19 to 38 years of age in four cities from 2007 to 2017.
The 29,862 samples in Boston came from 653 donors. The 50,462 samples from Los Angeles came from 969 donors. The 13,399 samples in New York City came from 379 donors. And the 26,368 samples from Palo Alto, California, came from 478 donors.
All counts decreased during the 11-year study period except total sperm count and total motile sperm count in New York City.
|Table. Geographic Trends in Semen Quality From 2007 to 2017|
|Total sperm count (millions)|
|New York City||+2.75||.3369|
|All four cities||–2.94||<.0001|
|Sperm concentration (millions/mL)|
|New York City||–0.17||.8984|
|All four cities||–1.76||<.0001|
|Total motile sperm (millions)|
|New York City||+3.39||.1500|
All four cities
"The findings of declining sperm count and motility have been reported in many other cohorts around the world, as well as in the United States," Chang said. "What did surprise us, however, was the magnitude of the decline and the fact that individual geographic areas were affected differently."
"We don't know why New York City appeared to be so different," she told Medscape Medical News.
"It is possible that there are environmental or lifestyle differences that account for these findings, but we can only speculate causality until we have prospective studies that are designed to investigate this question," she explained.
The researchers have not yet been able to determine the cause of the decline, which is likely multifactorial.
"Many research studies have been focused on exposure to endocrine disruptors, like bisphenol A, industrial chemicals, heavy metals, and pollution, whereas others have pointed toward changes in our modern lifestyle, including decreased physical activity, increasing body mass indices, and less healthy diets," said Chang.
A Concerning Trend
"The trend toward lower sperm counts in this study is concerning," said ASRM President Peter Schlegel, MD, from New York–Presbyterian Hospital/Weill Cornell Medical Center in New York City.
"Whether the causes underlying it are environmental or lifestyle-related, they will be difficult to parse out. Pollution, endocrine-disrupting chemicals, poor exercise habits, and poor diet could all play a role," he told Medscape Medical News.
"The exceptionalism of New York sperm donors is intriguing, but maybe not surprising," he noted. "New Yorkers tend to be physically active and our water system provides some of the cleanest and highest-quality water in the United States."
California Cryobank in Los Angeles provided the study data. Chang and Schlegel have disclosed no relevant financial relationships.
American Society for Reproductive Medicine (ASRM) 2018 Scientific Congress: Abstract 0-126. Presented October 9, 2018.
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Cite this: Sperm Count and Motility Declining in United States - Medscape - Oct 18, 2018.