A study published in The World Journal of Men’s Health provides an up-to-date report on the geographical differences in sperm parameters amongst a gaggle of men residing in six regions of continental US.

Study: Geographic Differences in Semen Quality amongst a Cohort of American Men Using Mail-in Sperm Testing Kits. Image Credit: sulit.photos/Shutterstock

Background

Infertility is a number one disability affecting about 8 – 12% of couples worldwide. Amongst infertility cases, roughly 40% are related to male factor infertility. Semen analyses, including sperm count, concentration, motility, and morphology, are considered the most effective indicators of male fertility status. 

Sperm quality will be affected by several aspects, including age, body mass index, smoking and drinking habits, physical activity level, educational background, stress, and certain medical conditions. Furthermore, there’s evidence suggesting that the geographical location of a person can influence his sperm quality.

The correlation between geographical location and sperm quality has been studied extensively in lots of countries outside the USA. Nonetheless, large-scale epidemiological studies on male fertility are absent in continental US.

In the present study, scientists have determined geographical differences in sperm quality amongst a gaggle of men residing in six different regions of continental US, including Northeast, Southeast, Midwest, West, Pacific, and Southwest. 

Study design

The study was conducted on 5,822 men who self-requested semen evaluation between 2019 and 2021. Not one of the participants had a self-reported history of male factor infertility. Depending of the geographical location, the participants were categorized into six groups, including Northeast, Southeast, Midwest, West, Pacific, and Southwest. 

Semen samples were collected from the participants using a validated at-home mail-in semen collection kit. The participants were instructed to self-collect semen samples using the kit delivered to their home. Afterward, the samples were shipped overnight to the laboratory for semen evaluation, which included sperm count, motility, and morphology.

Essential observations

The comparative analyses conducted within the study revealed that the typical sperm concentration, total variety of motile sperm, and total motility were lower in participants from the West region than in participants from other studied locations. A discount in total sperm count and progressive motility was also observed in participants from the Southwest region.

Participants from the Midwest region exhibited higher total motile sperm count and total sperm motility. Similarly, participants from the Northeast region showed higher average sperm concentration and total sperm count.  

The comparison of semen parameters between the participants aged below and above the age of 35 years revealed variations in sperm concentration, total sperm count, total motile sperm, and total and progressive motility. These differences between younger and older participants were significant within the Northeast and Pacific regions but not the Midwest region.

A complete of 1,654 participants were identified to have low sperm count (oligozoospermia) within the study population. Of them, about 50% were aged below 35 years. Notably, no significant difference within the prevalence of oligozoospermia was observed between younger and older participants, no matter geographical locations. Nonetheless, a comparatively higher prevalence of oligozoospermia was observed in participants from the Southwest and Southeast regions.

The multivariable evaluation conducted within the study revealed that the geographical differences in sperm quality amongst participants should not affected by their age and body mass index.

Study significance

The study provides a radical overview on the impact of geographical locations on sperm quality of men residing in six different locations of continental US. Based on the study findings, people from the Midwest and Northeast regions have higher sperm quality than those from the Southwest and West regions.

As mentioned by the scientists within the article,

this study will pave the best way right into a deeper discussion of the interplay between geography, social determinants of fertility care and semen quality.”