Over the past five decades, numerous studies have reported declining semen quality.
The average sperm count has dropped by half in men, from 99 million sperm per millilitre to 47 million per millilitre. This number is on the verge of hitting the World Health Organization's (WHO) measure of low-quality sperm, which is 40 million per millilitre.
Researchers attribute the sharp decline to a combination of environmental factors, including endocrine disruptors, pesticides, and radiation, as well as lifestyle habits like diet, alcohol consumption, stress, and smoking.
Scientists from UNIGE and Swiss TPH investigated whether mobile phones also play a role in this decline. The study involved 2,886 Swiss men between 18 and 22, recruited between 2005 and 2018 at six military conscription centres.
Participants completed detailed questionnaires about their lifestyle habits, general health, and mobile phone usage frequency, as well as where they typically stored their phones when not in use.
The findings revealed an association between frequent mobile phone use and lower sperm concentration. Men who used their phones more than 20 times a day had a 21 per cent decrease in sperm concentration among frequent users.
Constant phone use reduced average sperm concentration to 44.5 million per millilitre, compared to 56.5 million per millilitre in men who used their phones less than once a week.
The study also noted that this association was more pronounced in the earlier study period (2005-2007) and gradually decreased with time (2008-2011 and 2012-2018).
Researchers suggest that this trend may have a link to the transition from 2G to 3G and then to 4G mobile networks, which resulted in reduced transmitting power of phones.
"Previous studies evaluating the relationship between the use of mobile phones and semen quality were performed on a relatively small number of individuals, rarely considering lifestyle information, and have been subject to selection bias, as they were recruited in fertility clinics. This has led to inconclusive results," says study co-author Rita Rahban, senior researcher and teaching assistant in the Department of Genetic Medicine and Development in the Faculty of Medicine at the UNIGE and at the Swiss Center for Applied Human Toxicology, in a university release.
The study also explored the positioning of mobile phones, such as carrying them in trouser pockets, but did not find a clear association with lower semen parameters. Researchers noted, though, that the number of participants who did not carry their phones close to their bodies was too small to draw robust conclusions on this specific aspect.
One limitation of the study was that it relied on self-reported data, which may not always accurately reflect actual mobile phone usage. To address this limitation, a new study funded by the Federal Office for the Environment (FOEN) is set to launch in 2023.
It aims to directly measure exposure to electromagnetic waves and different types of mobile phone usage (calls, web browsing, sending messages) to assess their impact on male reproductive health and fertility potential.
Researchers also intend to investigate further the mechanisms behind these observations, including whether the microwaves emitted by mobile phones have a direct or indirect effect, whether they cause a significant increase in testicular temperature, and whether they influence the hormonal regulation of sperm production.
The study is published in the journal Fertility & Sterility. Previous studies have also found that cell phone radiation causes sharp spikes in Alzheimer's disease.
