Geographic Differences in Semen Quality of Fertile U.S. Males. (Research)
Swan, Shanna H., Brazil, Charlene, Drobnis, Erma Z., Liu, Fan, Kruse, Robin L., Hatch, Maureen, Redmon, J. Bruce, Wang, Christina, Overstreet, James W., Environmental Health Perspectives
Although geographic variation in semen quality has been reported, this is the first study in the United States to compare semen quality among study centers using standardized methods and strict quality control. We evaluated semen specimens from partners of 512 pregnant women recruited through prenatal clinics in. four U.S. cities during 1999-2001; 91% of men provided two specimens. Sperm concentration, semen volume, and motility were determined at the centers, and morphology was assessed at a central laboratory. Study protocols were identical across centers, and quality control was rigorously maintained. Sperm concentration was significantly lower in Columbia, Missouri, than in New York, New York; Minneapolis, Minnesota; and Los Angeles, California. Mean counts were 58.7, 102.9, 98.6, and 80.8 x [10.sup.6]/mL (medians 53.5, 88.5, 81.8, and 64.8 x [10.sup.6]/mL) in Missouri, New York, Minnesota, and California, respectively. The total number of motile sperm was also lower in Missouri than in other centers: 113, 196, 201, and 162 x [10.sup.6] in Missouri, New York, Minnesota, and California, respectively. Semen volume and the percent morphologically normal sperm did not differ appreciably among centers. These between-center differences remained significant in multivariate models that controlled for abstinence time, semen analysis time, age, race, smoking, history of sexually transmitted disease, and recent fever (all p-values < 0.01). Confounding factors and differences in study methods are unlikely to account for the lower semen quality seen in this mid-Missouri population. These data suggest that sperm concentration and motility may be reduced in semirural and agricultural areas relative to more urban and less agriculturally exposed areas. Key words: agriculture, geography, semen quality, sperm concentration, sperm morphology, sperm motility.
Historically, semen parameter studies have included highly selected and nonrepresentative subgroups such as compensated sperm donors, prevasectomy patients, or infertility clinic populations. Moreover, measures of semen quality are very sensitive to the methods of semen collection (including abstinence time) and analysis, which vary significantly among study sites. Further, most analyses of temporal trends and geographic variation in semen parameters have been retrospective and subject to confounding by factors such as smoking or recent high fever that cannot be well controlled retrospectively. These studies have been conducted almost exclusively at andrology centers, which are usually located in urban areas, primarily in Western Europe and North America.
Nonetheless, over the past decade several authors have reported large geographic differences between cities in mean sperm concentration. For example, an international study of testosterone-induced azoospermia found that mean pretreatment sperm concentrations of normal men in nine countries ranged from 52.1 x [10.sup.6]/mL in Bangkok, Thailand, to 103.5 x [10.sup.6]/mL in Melbourne, Australia [World Health Organization (WHO) Task Force on Methods of Regulation of Male Fertility 1996]. A wide range of sperm concentration was also reported in eight cities in France (Auger and Jouannet 1997). Several recent studies suggest that wide variation is also present among cities in the United States. Wittmaack and Shapiro (1992) examined sperm concentration between 1978 and 1987 in Madison, Wisconsin; mean sperm concentration during this time was approximately 80 x [10.sup.6]/mL. Paulsen et al. (1996) reported a geometric mean of about 50 x [10.sup.6]/mL in Seattle, Washington, during 1972-1993. A recent study in California (Fenster et al. 1997) found a median sperm concentration of 64 x [10.sup.6]/mL. Fisch and Goluboff (1996) reported large differences in mean sperm concentration in prevasectomy patients from Los Angeles, California; Minneapolis, Minnesota; and New York City, New York, with low concentration in Los Angeles compared with Minneapolis and New York City (72. …