Impact of Environmental and Socioeconomic Factors on Semen Quality in the United States

Abstract

ABSTRACT Introduction It has been stated that sperm counts worldwide have declined by as much as 50% since 1973, with increasing environmental pollutants cited as one of many possible root causes. Recent theories challenge the validity of these contentious claims, such as the sperm count bioavailability (SCB) hypothesis, which asserts that global sperm health remains highly heterogenous across bodies, ecologies, and even time periods. Specifically, the impact of ecological factors on sperm health in the United States remains grossly understudied. Objective To examine the effect of environmental and socioeconomic factors, such as air quality, rurality, median income, and poverty rates, on sperm quality in the United States. Methods An ecological study was conducted using a nation-wide sample obtained from Dadi Kit, a company which produces at-home sperm testing kits, containing the zip code, age, and semen analyses for all subjects consenting to research. Subjects were linked via zip code to national, geographical databases on Air Quality Index (Environmental Protection Agency), rurality (Federal Office of Rural Health Policy), median household income (Census Bureau), and poverty rates (Census Bureau). Comparative analyses were conducted on Stata (College Station, TX). Linear regression models adjusted for age were used to analyze associations of sperm concentration (millions/mL of semen), motility (%), and semen volume (mL) with each exposure variable. Results A total of 1,343 male subjects with a median age of 32 (interquartile range [IQR]: 28-38) were included, representing 1,035 unique zip codes and 306 United States counties. Median values of sperm concentration, motility, and semen volume were 126.8 million/mL (IQR: 64.2-226.5 million/mL), 25.9% (IQR: 15.7-38%), and 2.2 mL (IQR: 1.4-3.6 mL), respectively. As illustrated in Table 1, air quality index, median household income, and poverty rates were not significantly correlated with any of the three semen parameters measured. A significant negative correlation between rurality and sperm motility was observed (P=.04), yet no association was observed with sperm concentration or semen volume. Conclusions Our study found no apparent link between air quality, median income, or poverty rates and any of the semen parameters measured in our nation-wide sample, while rurality was negatively associated with sperm motility only. Further longitudinal studies at the individual level are needed to dismiss a link between socioeconomic factors and sperm quality in the United States. Disclosure Yes, this is sponsored by industry/sponsor: Dadi Kit Clarification No industry support in study design or execution Any of the authors act as a consultant, employee or shareholder of an industry for: Dadi Kit