The article explores a study suggesting an association between frequent mobile phone use and reduced sperm count in young men, while experts emphasise the need for caution due to potential confounders and the complexity of proving causation.

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On 31 October 2023, Fertility and Sterility Journal published a paper by researchers from the Universities of Geneva and Basel, Switzerland suggesting an association between self-reported mobile phone use and the semen quality of young men.

How prevalent is infertility in any community?

Approximately one in six couples suffers from infertility, which the researchers defined “as the inability to conceive a child after 1 year of regular, unprotected sexual intercourse. The authors added:

” Around half of the clinical causes of infertility are attributable to the male partner, but the aetiology of poor semen quality remains insufficiently understood". 

Sperm count has been reportedly found to have declined significantly over recent decades. No one has thus far identified the possible causes. People have associated many environmental and lifestyle factors such as obesity, smoking, alcohol consumption, and psychological stress, among others, with this decline.

Based on reviews of existing literature, the authors found that RF-EMF exposure has also been linked to a significant increase in abnormal histological changes in seminiferous tubules, suggesting an impairment of male fertility in mice.

Effects are not always reproducible

1. They observed that these effects however are not always reproduced, mainly because of protocol differences, despite the numerous animal studies conducted since the 1970s. Also, there are fundamental differences between spermatogenesis in humans and rodents.
2. The researchers found that experimental studies on human sperm in vitro, comparing RF-EMF-exposed with unexposed samples, mostly reported a significant increase in DNA fragmentation and reduced motility.
3. “However, exposure set-ups in these studies were mostly insufficiently characterised and are unlikely to be comparable to in vivo exposure from typical mobile phone use because they were short-term exposures occurring directly on semen after ejaculation” they cautioned
4. The bias related to exposure-induced temperature increase may be another plausible explanation for the observed effects
5. They revealed that “In humans, observational studies investigating the relationship between mobile phone use and reproductive health have associated primarily a high frequency of mobile use with decreased sperm motility, morphology, and viability, although effects on sperm concentration were more equivocal”.
6. The researchers found that the number of observational studies investigating the impact of mobile phone use on reproductive health and semen quality is limited. They recruited participants when they visited fertility clinics. Such studies included a relatively small number of individuals and adjusted for only a few confounders.
7. Thus, selection, confounding, and publication bias are also of concern; in addition, in such a setting, retrospective reports of mobile phone use are vulnerable to recall bias

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Present study

In the present study, researchers analysed the data collected from young Swiss men from the general population without prior knowledge of their fertility status. Participants provided details on their mobile phone use habits when they answered a questionnaire, making recall bias very unlikely or impossible.

After adjusting for numerous potential confounding factors, they examined the association between self-reported mobile phone use, position of the phone when not in use, and semen parameters. Because recruitment of these men began in 2005, before the widespread use of smartphones, they could evaluate the association between frequency of use and semen parameters over different time periods.

The researchers investigated the association between mobile phone exposure and semen parameters in a nationwide cross-sectional study in Andrology laboratories close to 6 army recruitment centres. In total, the researchers included 2886 men from the general Swiss population, 18–22 years old; they were recruited between 2005 and 2018 during military conscription.

Each participant delivered a semen sample and completed a questionnaire on health and lifestyle, including the number of hours they spent using their mobile phones and where they placed them when not in use.

By using appropriate mathematical models the researchers evaluated the association between mobile phone exposure and semen parameters such as volume, sperm concentration, total sperm count (TSC), motility, and morphology.

Results

In total, 2759 men answered the question concerning their mobile phone use, and 2764 gave details on the position of their mobile phone when not in use.

The study group has some notable features:

1. They showed descriptive results for the entire population as well as after stratification of men in 5 groups according to the frequency of their mobile phone use:

• <once per week
• 1–5 times per day
• 5–10 times per day
• 10–20 times per day
• >20 times per day

Substantial variation in exposure was therefore available, ranging from men with little or no mobile phone use (< once a week, 8.6% equivalent to 223 men) to those who used it >20 times a day (22%, equivalent to 608 men).

2. Unlike most previous studies, all participants completed a comprehensive questionnaire on potential confounding factors such as BMI, maternal smoking, cigarette, and alcohol consumption. These variables were taken into account in every model that was examined. Information bias in this regard is considered to be limited because participants were not aware of the results of their semen analysis when they completed the questionnaire, and neither the participants nor the researchers knew that this association study would be conducted.
3. Men were asked to provide details of their mobile phone use in the period immediately before completing the questionnaire, which also makes recall bias very unlikely...
4. Given that the researchers have included some of the most plausible potential confounders, this is an indication that residual confounding from factors that we could not consider does not play a substantial role in this study

In the adjusted linear model, a higher frequency of mobile phone use (>20 times per day) was associated with a lower sperm concentration and a lower Total Sperm Count (TSC). In the adjusted logistic regression model, this translates to a 30% and 21% increased risk for sperm concentration and TSC to be below the World Health Organization reference values for fertile men, respectively.

The researchers found the inverse association to be more pronounced in the first study period (2005–2007) and gradually decreased with time (2008–2011 and 2012–2018). They did not observe consistent associations between mobile phone use and sperm motility or sperm morphology. It was not discovered that carrying a cell phone in one's pants pocket was linked to reduced semen parameters.

Conclusion

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Expert reaction to the study

The study attracted the critical appraisal of many specialists.

Professor Alison Campbell, Chief Scientific Officer, of Care Fertility noted that this is a relatively large study of over 2500 men conducted over 13 years to examine the possible association of radiofrequency electromagnetic fields (RF-EMF) with semen parameters. The research reported decreasing sperm numbers with increasing mobile phone usage.

“We know that many lifestyle factors can affect male fertility, but we have almost certainly not identified all of them” Professor Campbell cautioned. “This research considered and adjusted for some of them and also involved the men completing detailed questionnaires about their health and lifestyle”. However, there could be other causes of the decline in sperm numbers that were observed.

“The authors suggested that more studies are required to confirm whether mobile phones were the cause of the reduction in sperm numbers that was seen. There is currently no confirmed explanation of the biology or mechanisms behind this finding, as the research has not yet been done.

“Interestingly, sperm morphology (shape) and motility were not seen to decline, with increased use of mobile phones, as sperm numbers did. Whilst sperm numbers matter, the ability of sperm to swim, have healthy intact DNA and be the right shape, is at least as important.

Professor Campbell acknowledged that this is a fascinating and novel study which should not cause alarm or drastic changes in habits.

Professor Allan Pacey of Andrology at the University of Manchester recalls that he has been asked many times over the past decade whether there is any link between mobile phones and male fertility. However, he has been largely unconvinced by the data which has been published to date.

In 2022, he summarised his position on the topic in a statement he gave to the Science Media Centre. He asserted that very little has changed in the interim. He was then reviewing a conference abstract (not a published paper) presented at the American Society for Reproductive Medicine 2022 meeting,

“This appears to be a well-conducted laboratory study investigating the effects of 4G, 5G and wifi signals on sperm motility and viability in ejaculated human sperm. The data shows that sperm exposure to wifi reduces sperm motility and viability. I have no problem with this conclusion on the basis of the information presented in this abstract, but we need to be cautious about how this is interpreted in a real-world setting” he cautioned.

Then he stated thus:

1. “First, it is important to note that sperm in the male body before ejaculation do not swim. Therefore, it is a leap of faith to assume that the damaging effects of wifi signals might affect un-activated sperm in men’s bodies in the same way as the authors of this study have shown for ejaculated sperm in the laboratory. This may be the case, but this study does not show this. I do not underestimate the technical difficulty in doing this kind of experiment on un-activated sperm that have not been ejaculated.”
2. “Second, because sperm only begin to swim at the point of ejaculation, they are only really motile once they are inside the female body (in natural conception cycles) or in a cup or dish (if they are being used for assisted reproduction). Again, it is a leap of faith to assume that sperm inside a woman might be exposed to the same level of wifi signals used in these experiments. In assisted reproduction, it is not standard practice to have mobile phones in laboratories in close proximity to samples of sperm. Therefore, again, I am wondering about the real-life interpretation of this data.”
3. There is certainly reason to be concerned about threats to male reproductive health, but this study does not really help us with that question. It is an artificial experimental set-up and we should be careful not to over-interpret the results. Robust epidemiological statistics about male fertility and mobile phone use are what we are missing. In my opinion, this should be our priority.

Finally, Professor Pacey disputed the authors’ claim that the impact of wifi on sperm has not previously been investigated by drawing attention to the paper:

“Avendano C, Mata A, Sanchez Sarmiento CA, Doncel GF. The use of laptop computers connected to the internet through Wi-Fi decreases human sperm motility and increases sperm DNA fragmentation. This showed similar results using wifi from a laptop computer rather than a smartphone.” He added

Professor Pacey acknowledged that the study by the Swiss researchers is a little step forward in the debate because this is a large epidemiological study which appears to have been very well conducted.

“The study is not perfect, and the authors of it acknowledge that (one of the main criticisms being that mobile phone use was self-reported), but it is a study in the real world – and that is good in my opinion. However, we should be cautious about its interpretation as it only shows an association between mobile phone use and semen quality. We cannot be sure that the mobile phone is not a surrogate marker for another aspect of the men’s lifestyle or occupation that is the real cause of any changes to their sperm quality. I am intrigued by the observation that the biggest effect was apparently seen with older 2G and 3G phones compared to modern 4G and 5G versions. This is not something I am able to explain and you’d have to speak to an expert in electromagnetic radiation to better understand that.’ He suggested.

“Finally, whilst this paper gives the researchers a clear sense of direction for their future studies (which they mention in the paper), I am not sure it really changes the advice I would give to men who are concerned about their fertility. If men are concerned, then keeping their phones in a bag and limiting their use is a relatively easy thing for them to do. But there is currently no evidence that will improve their sperm quality (that would need a randomised controlled trial). As for me, I will be continuing to keep my phone in my trouser pocket.” He added

Professor Malcolm Sperrin, Institute of Physics and Engineering in Medicine (IPEM) Fellow, also acknowledged that this is a well-designed study from a highly respected organisation that has the intent to correlate mobile phone use with sperm quality in a relevant young population.

“The ethics approval is important in that care is given to ensure the population is appropriately chosen. The findings certainly stimulate the need for further research. However, there is a vital need on the part of the ‘lay’ reader to avoid over-interpreting the findings and drawing conclusions that are difficult to justify.” He warned

“The use of a questionnaire to determine phone use is likely to be associated with large error bars but it is challenging to see how else this data could be obtained; self-reporting is notoriously prone to uncertainties. There are likely to be numerous confounding factors which the authors, and future researchers, will be able to investigate such as the hypothesis that increased use of the phone is associated with anxiety which is then the cause of lower sperm quality. This paper is a good driver to more research in this very difficult area.”

This writer feels that the researchers could have collected the time of usage objectively from the phone records of the subjects rather than relying on the memory of each of them. Maybe there are privacy issues which came in the way.

Epidemiological studies are complicated. In December 2010, Professor Matt Parker at the mathematics department at Queen Mary, University of London, demonstrated it. He tabulated the number of mobile phone masts in each county across the United Kingdom and then matched it with the number of live births in the same counties.

He found the correlation so strong that in areas above normal numbers of mobile phones, he could predict how many more births above the national average occurred. Parker concluded that for every extra mobile phone base station in an area, the number of births goes up by an average of 17.6 babies!

As the population of an area goes up so do both the number of mobile phone users and the number of people giving birth. Instinctively, we tend to assume that correlation means that one factor caused the other. Prof Parker’s hilarious title of his article in The Guardian (20 December 2010) was: “Mobile phone radiation linked to people jumping to conclusions."

Hill’s Criteria

In this context, budding epidemiologists must learn the Bradford Hill criteria, otherwise known as Hill's criteria for causation. These nine criteria that the researcher should evaluate are the strength of association, consistency, specificity, temporality, biological gradient, plausibility, coherence, experiment and analogy listed in the classic paper by Hill AB.

Disclaimer- The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or position of M3 India.

About the author of this article: Dr K S Parthasarathy is a former Secretary of the Atomic Energy Regulatory Board and is a medical physicist with a specialisation in radiation safety and regulatory matters.