Lately sperm has been all over the front pages. It began in 1992 with University of Copenhagen researcher Niels Skakkebaek, whose meta- analysis of world fertility studies since the 1930s suggested a dramatic decline in global sperm counts. New evidence suggests Skakkebaek’s pronouncements may have been a case of premature you-know-what. In an article published last May, Harry Fisch, director of the Male Reproductive Center at Columbia Presbyterian Medical Center in New York City, reviewed sperm counts in samples from 1,283 men in New York, Minnesota, and California who had banked sperm before a vasectomy. The data, spanning 1970 to 1994, showed sperm counts on the rise in all three states.
Fisch believes Skakkebaek’s gloomy findings may have reflected geographic differences rather than long-term changes. Most of Skakkebaek’s pre-1970 data came from New York, whereas later data came from developing countries--where sperm counts are generally lower. If Fisch’s data are any indication, New York men produce more of the wiggly gametes than most. The Empire State’s sperm counts averaged 131 million per milliliter; the California dudes put out a relatively meager 73 million per milliliter. (A milliliter is about one-thirtieth of an ounce.)
What is it about New York men? What does geography have to do with fertility? Here’s the answer, says Fisch. I haven’t a clue. Fisch points out that there are not only regional variations in sperm counts but also large fluctuations from one year to the next, both in populations and in individuals. A man’s sperm count goes up and down quite dramatically. We’ve found seasonal variations--higher in winter, lower in summer. Again, we don’t know why. Which years researchers choose to compare, in other words, will affect their conclusions about long-term sperm count trends. You can look at certain sets of years and say, ‘Wow, look at this decline,’ says Fisch. You can look at other years and say, ‘Wow, what an increase.’ All we’re saying is that there’s really no conclusive evidence of any change over the last 25 years. You need to evaluate over a longer period--say, 100 years. Perhaps the task will fall to Fisch’s progeny, which, given his address, could be numerous.
Fisch believes Skakkebaek’s gloomy findings may have reflected geographic differences rather than long-term changes. Most of Skakkebaek’s pre-1970 data came from New York, whereas later data came from developing countries--where sperm counts are generally lower. If Fisch’s data are any indication, New York men produce more of the wiggly gametes than most. The Empire State’s sperm counts averaged 131 million per milliliter; the California dudes put out a relatively meager 73 million per milliliter. (A milliliter is about one-thirtieth of an ounce.)
What is it about New York men? What does geography have to do with fertility? Here’s the answer, says Fisch. I haven’t a clue. Fisch points out that there are not only regional variations in sperm counts but also large fluctuations from one year to the next, both in populations and in individuals. A man’s sperm count goes up and down quite dramatically. We’ve found seasonal variations--higher in winter, lower in summer. Again, we don’t know why. Which years researchers choose to compare, in other words, will affect their conclusions about long-term sperm count trends. You can look at certain sets of years and say, ‘Wow, look at this decline,’ says Fisch. You can look at other years and say, ‘Wow, what an increase.’ All we’re saying is that there’s really no conclusive evidence of any change over the last 25 years. You need to evaluate over a longer period--say, 100 years. Perhaps the task will fall to Fisch’s progeny, which, given his address, could be numerous.
