Sperm quality has decreased substantially in the past few decades. In the past 50 years, sperm counts have halved and the rate of decrease seems to be accelerating. A new study shows at least that a part of that may be linked to mobile phones — and suggests we should perhaps pay more attention to our virtual assistants.

Measuring semen quality is not straightforward. Semen quality requires a complex assessment of parameters such as sperm concentration, sperm count, and sperm morphology. The World Health Organization estimates that a man with a sperm concentration below 40 million per milliliter may have difficulties conceiving, and if the sperm concentration drops below 15 million per milliliter, the man will probably take more than one year to conceive (if actively trying).

Globally, the average sperm concentration in individuals has dropped from around 99 million to 47 million per milliliter — getting closer to a dangerous threshold. This phenomenon is thought to be linked to many different causes. A part of it comes from our lifestyle. We’re living less active lifestyles, eating unhealthy diets, drinking alcohol and smoking — all of this can be detrimental to sperm quality. Things like pesticides can also produce an effect.

But another potential culprit could be radiation.

Some of that radiation may come from our mobile phones. The new study focused on the Swiss population, and in particular on men aged 18 to 22 from military conscription centers. Overall, the data included 2523 Swiss men.

Main study findings

The study found several causes for concern.

1. Sperm Concentration: The median sperm concentration was 48 million/mL, considerably low compared to the World Health Organization’s (WHO) reference values for fertile men.
2. Percentage of Suboptimal Semen Quality: 17% of participants had sperm concentrations below 15 million/mL, 25% had less than 40% motility, and 43% had less than 4% normal forms.
3. Overall Impact: A staggering 62% of the men had one or more semen parameters below WHO thresholds.
4. Geographical and Lifestyle Factors: No significant differences were found in semen quality based on location, urbanization, and linguistic factors within Switzerland​​.

A parallel analysis presented in the same study revealed an increase in testicular cancer rates in Switzerland, from 7.6 cases per 100,000 in 1980 to 10.4 per 100,000 in 2014. This rise in testicular cancer, alongside declining semen quality, underscores a broader concern regarding male reproductive health.

Is the mobile phone to blame?

The men in the study “completed a detailed questionnaire related to their lifestyle habits, their general health status and more specifically the frequency at which they used their phones, as well as where they placed it when not in use,’’ explains Serge Nef, from the Swiss Centre for Applied Human Toxicology, who co-directed the study.

The data showed an association between frequent mobile phone use and lower sperm concentration. The median sperm concentration was significantly higher (56.5 million/mL) in the group who did not use their phone more than once a week. Meanwhile, in the group that used their phone more than 20 times a day, sperm concentration was lowest (44.5 million/mL). This difference corresponds to a 21% decrease in sperm concentration. The position where people kept their phones was not associated with lower semen parameters.

There is another piece of information that seems to suggest that phones may have an effect. The study was carried out over three periods, and this association was strongest in the first period (2005-2007) and gradually decreased with time (in the periods 2008-2011 and 2012-2018).

‘‘This trend corresponds to the transition from 2G to 3G, and then from 3G to 4G, that has led to a reduction in the transmitting power of phones,’’ explains Martin Röösli, associate professor at Swiss TPH.

How phones affect sperm

Electromagnetic waves from devices like mobile phones emit a type of energy that can be absorbed by nearby tissues. This absorption could interfere with the natural cycle of sperm cell development and even increase the rate at which sperm are destroyed. Potentially, this could affect fertility by reducing the number of healthy sperm available.

But studies have found conflicting evidence on this.

Various studies have been done to assess this effect. Some of these studies were done in labs with animals like rats or with human sperm in test tubes. These studies on rats found that the radio waves might mess with the normal cycle of cells that lead to sperm creation, increase the number of sperm that die, and cause changes in the testicles.

However, some studies have found no evidence of this happening and it’s tricky to say for sure whether this effect actually exists. Furthermore, what happens in animals doesn’t always match up with what happens in humans, especially since the way sperm is made in humans and rodents isn’t exactly the same.

When it comes to human sperm tested in the lab, studies often found that sperm exposed to these radio waves had more DNA damage and didn’t move as well. But the way these studies exposed sperm to radio waves doesn’t really match how we’re exposed to them from using our phones, since these were short experiments done right after the sperm was collected. Also, any warming up of the sperm from the radio waves could also explain why the sperm didn’t do so well in these experiments.

Putting this into context

This decline in semen quality mirrors global trends and is among the lowest observed in Europe. Earlier studies suggested environmental and lifestyle factors as crucial influencers of this decline. This new research shows some of the strongest correlation linking mobile phones to sperm quality — but there are several limitations of this study.

The participation rate in the study was relatively low at 5.3%. This raises concerns about the representativeness of the sample. Even though the study reached out to a large portion of the young male population, the findings may be influenced by self-selection bias, where those who chose to participate might differ in key aspects from those who did not​​.

Also, while the study covered various regions of Switzerland, the extent to which these findings can be generalized to other countries or regions is uncertain. Different environmental, lifestyle, and genetic factors in other regions could lead to varying semen quality outcomes. There’s also the fact that self-reporting is notoriously unreliable and that the position of the phone did not seem to matter. All these are significant limitations that may point to a correlation and not a causation.

Nevertheless, despite the limitations, the study rings an important alarm bell.

A question worth pursuing

The Swiss study on semen quality is a crucial addition to the growing body of research on male reproductive health. It not only sheds light on the current state of male fertility in Switzerland but also contributes to the global conversation on this pressing issue. As we move forward, a multi-disciplinary approach involving medical professionals, researchers, policymakers, and the public will be vital in addressing these challenges and ensuring a healthy future for the next generations.

The next step for researchers is to identify the mechanisms through which mobile phone use affects sperm quality — only after this can a clear conclusion be drawn.

‘‘Do the microwaves emitted by mobile phones have a direct or indirect effect? Do they cause a significant increase in temperature in the testes? Do they affect the hormonal regulation of sperm production? This all remains to be discovered,’’ concludes Rita Rahban.

In the meantime, we should be thankful that modern mobile technologies (4G and 5G) are more efficient. If mobile phones do indeed affect sperm quality, these newer technologies can substantially reduce the impact.

The study was published in the journal Fertile and Sterility.