Global sperm counts have been declining for decades and although researchers have many hypotheses, no one knows exactly why. A new study out of Switzerland may add another potential risk factor to the list: mobile phones.

After analyzing the semen samples of more than 2,800 young men, Swiss researchers found an association between a higher frequency of self-reported mobile phone use and lower sperm concentration in a study published in the journal Fertility and Sterility.

They did not find a difference in sperm motility or morphology between the different types of phone users. They also didn't find any evidence indicating that storing the phone in the pocket, rather than in a backpack, for example, plays a role in sperm concentration.

The researchers conducted the study from 2005 to 2018. They found that the association between high phone use and low sperm count was more pronounced during the first years of the study than at the end.

"This pattern is in line with the transition to new technologies, mainly from 2G to 3G and 4G, and the corresponding decrease in the phone's output power," the researchers wrote.

Factors that impact fertility

The study adds mobile phones to a long list of factors that other researchers have found could mess with fertility: smoking, obesity, alcohol, psychological stress and the so-called "endocrine disrupting" chemicals found in pesticides and the plastic wrappers that package the vegetables we buy at the store.

The research provides some evidence to growing concern over the past decades that the radiofrequency electromagnetic fields (RF-EMFs) emitted by mobile phones have a negative impact on human reproductive health.

Up until now, studies looking into this potential association have only been facilitated on mice or on sperm in vitro. This study marks the first facilitated in the "real world", which outside researchers say is positive.

"The study is not perfect, and the authors of it acknowledge that (pointing to self-reporting of mobile phone usage), but it is a study in the real world – and that is good in my opinion," Professor Allan Pacey of Andrology at the University of Manchester, who was not involved in the research, said in a statement.

Background

Infertility affects about 17% of couples worldwide, with about 50% of the cases attributable to the male partner. While the cause of poor semen quality is yet to be thoroughly understood, various factors such as obesity, alcohol consumption, smoking, and stress are known to be associated with a reduced sperm count.

The alarming rise of the use of mobile phones and the consequent exposure to radiofrequency electromagnetic fields (RF-EMFs) is shown in experimental and observational studies to affect the reproductive health of males concerning sperm count, morphology, motility, and viability. However, these studies are few and with various biases of concern. Therefore, researchers conducted a cross-sectional study examining the potential association between semen parameters, mobile phone use, and position when not in use in young Swiss men between 2005 and 2018.

About the study

In the present study, 5,605 men aged 18–22 years were surveyed across six centers in the country using questionnaires regarding their health and lifestyle as well as their parents’ preconception period. The men were also asked about the duration and frequency of mobile use (rarely, a few times per week, 1–5 times per day, 5–10 times per day, 10–20 times per day, >20 times per day) and the place where they kept the phone (in a jacket pocket, pant pocket, belt carrier, or elsewhere) when not in use.

A total of 2,866 men were physically examined for their genital anatomy, testicular volume, weight, and height, and they contributed semen samples to the study.. Semen analysis was performed based on guidelines of the World Health Organization (WHO) to determine the sperm concentration, TSC, motility, and morphology. Statistical analysis included the use of the Kruskal-Wallis test, Chi-square test, and adjusted logistic and linear regression models. Additionally, a sensitivity analysis was also performed by excluding the men with azoospermia (1%).

Results and discussion

It was found that men with a higher frequency of mobile usage were slightly younger (19 years) and had a higher body mass index (BMI = 22.8 kg/m²) as compared to men with a lower frequency of mobile use (BMI = 21 kg/m², age 20 years). Interestingly, while 56.5% of the men used their mobile phones less than once per week between 2005 and 2007, this proportion reduced to 5% between 2015 and 2018.

Men using mobile phones at a high frequency (>20 times a day) showed a 21% reduction in sperm concentration and a 22% TSC decrease as compared to those who rarely (less than once per week) used mobile phones. Significant exposure-response trends were observed across the complete exposure range in this group of men. Moreover, these men also showed a higher risk of having a sperm concentration and TSC below the WHO reference value for fertile men. The likelihood of having a lower-than-WHO-reference sperm concentration was significantly higher in men using mobile phones 5–10 times a day than those who rarely used it in the day or week (adjusted odds ratio = 1.409). The results appeared unchanged even when men with azoospermia were excluded from the study. Interestingly, the association between sperm concentration and mobile phone use was shown to be stronger during 2005–2007 and progressively reduced in the periods 2008–2011 and 2012–2018. The semen volume, sperm morphology, and motility were not found to be associated with the frequency of mobile use.

About 85.7% of the included men were found to store their mobile phones in their pant pockets (when not in use). However, the semen quality parameters were not found to be affected by the position of the mobile phone when not in use.

This is the most extensive study evaluating the effect of mobile-phone-based RF-EMF exposure on semen quality. The results are further strengthened by the fact that the studied sample of men came from a general population with an unknown fertility status. However, there are a few limitations to the study. It did not evaluate the daily RF-EMF absorption and relied solely on self-reported data for surveying mobile usage. Also, the characteristics of the phone, such as its brand, number of applications, network quality, use of ear accessories, and output power, were not recorded.

Conclusion

Given the dramatic increase in mobile phone usage globally, this study's findings provide essential insights into the effect of increased RF-EMF exposure on male reproductive health. In the future, conducting prospective studies that accurately measure RF-EMF exposure could help understand the mechanism of action underlying these effects.