Many city dwellers left urban environs for quieter, cleaner lives in farm country. A new epidemiological study suggests that a man's sperm may pay a subtle price for that rural life.
Researchers previously reported evidence suggesting regional variations in the amount and quality of men's sperm. However, most of this work didn't account for smoking, recent sexual abstinence, or other factors that can greatly affect sperm. Moreover, the studies were conducted strictly in big cities.
Shanna H. Swan of the University of Missouri–Columbia School of Medicine and her colleagues worked to avoid such shortcomings in their comparison of sperm from more than 500 fertile men in Minneapolis, Los Angeles, New York City, and the much smaller Columbia, Mo.
To the researchers' surprise, the quality of sperm from Columbia men, measured by the cells' motility, was just 56 to 70 percent of that from men in the bigger cities. Columbia men also registered only 57 to 72 percent a