TL/DR Male fertility is facing a silent crisis, with a staggering 51% decline in sperm concentration from 1973 to 2018. This comprehensive guide delves into the myriad of factors affecting sperm health, from heat exposure and psychological stress to caffeine, recreational drugs, and lifestyle choices like smoking and diet. With male infertility cases on the rise, understanding these key influencers and their impact on reproductive health is paramount. Dive into an in-depth analysis to uncover the modern challenges of male fertility and the solutions to combat them.
With all the fitness plans and the increase in men with gym memberships, you’d think that sperm production and quality wouldn’t be a major issue within fertility. However, the outcomes of many studies are consistent: the sperm produced by men are less healthy and there are fewer of them. Research shows that there has been a decline in male fertility over the years, despite the control measures that have been put in place for some of the risk factors such as obesity, genetic diseases, and hormonal imbalances. Another study has confirmed that there has been approximately a 51% decline in sperm concentration between 1973 and 2018.
Figure 1- showing the average sperm count of men worldwide in 1973 and 2018 (million sperm per millilitre of semen) adapted from Statista
These results reflect the necessity of further exploration into the mechanisms which negatively impact male fertility.
According to the WHO, infertility is defined as the ‘inability to achieve spontaneous pregnancy within a year of regular unprotected sexual intercourse. Male fertility is largely dependent on the ability to produce sperm that can successfully transmit paternal information to the next generation; it can be influenced by numerous factors.
The analysis of semen is a basic way to evaluate the fertility levels of men. Currently, the minimal parameters of semen, after 3 to 5 days of abstinence, have been defined by WHO and can be seen in Table 1 below.
16 million per ml
Morphology (The shape of the head, neck and tail of the sperm)
4% normal sperm morphology
Table 1- showing some of the main parameters assessed in a sperm sample
Some common causes of infertility in men include decreased sperm concentration, reduced sperm motility, abnormal sperm morphology and increased sperm DNA fragmentation. Currently, approximately a third of infertility cases are due to reproductive issues in men. Now, the crucial question is: which lifestyle factors are responsible for the decline in male fertility and what factors are affecting their viability? In this discussion, we'll delve into both common and less-known lifestyle elements that influence sperm viability.
The scrotum's temperature plays a vital role in safeguarding and ensuring the viability of sperm. Normally, the scrotum maintains a temperature approximately two to four degrees lower than the body's regular temperature. Sperm cells are very sensitive to temperature and research has shown that even a slight increase of 1 to 1.5 degrees in scrotal temperature can result in detrimental effects on sperm production, including a lower sperm count, reduced motility, and abnormal morphology.
Activities such as soaking in hot tubs, spending time in saunas, frequent cycling, and even wearing tight underwear can significantly impact scrotal temperatures. A study looked at the impact of wearing tight underwear on sperm and found that it raised scrotal temperatures. This rise in temperature led to decreased sperm concentration, reduced total sperm count, and impaired sperm motility, ultimately contributing to male infertility. Therefore, it is crucial for men concerned about their fertility to avoid activities that may further jeopardise their reproductive health.
Furthermore, the study revealed that increased scrotal temperature resulted in local tissue hypoxia and oxidative stress. Sperm cells are highly sensitive to oxidative stress, as it can induce DNA fragmentation, reducing the number of viable sperm cells and ultimately causing infertility.
Just like in many aspects of life, stress has the potential to affect our daily lives, and research also suggests that it can influence male fertility. A study examined the impact of psychological stress in men using a hospital anxiety and depression score (HADS). The results of the experiment revealed that men with a high HADS score exhibited lower levels of testosterone, the primary male sex hormone, as well as a reduced sperm count, diminished sperm motility, and a lower percentage of sperm displaying normal morphology, compared to men with a normal HADS score.
Stress can come in various forms and research has shown that stress stemming from a man's occupation and family life is negatively associated with semen quality. These forms of stress have been linked to an increased proportion of DNA-fragmented sperm cells. In contrast, life stress (such as experiencing discrimination, being diagnosed with an illness/disease) has been found to have no discernible impact on semen quality.
While no clear connections have been established between moderate caffeine consumption and semen quality, a closer examination of couples undergoing fertility treatment suggests that males who consumed caffeine had a lower probability of achieving a clinical pregnancy. Additionally, studies have shown a caffeine intake exceeding 3 cups per day is linked to an increased occurrence of DNA damage in sperm. On the contrary, another study has suggested that men with high caffeine intake display elevated testosterone levels compared to those with low coffee consumption, and, interestingly, higher caffeine intake is associated with a reduction in DNA fragmentation in sperm.
In summary, additional research is essential to delve deeper into the relationship between caffeine consumption and male fertility. The conflicting results in current research make it challenging to arrive at a definitive conclusion on this matter.
Marijuana and cocaine are among the most common illicit drugs used by many people and have been shown to have a negative effect on male fertility.
Marijuana, also known as cannabis, is a highly addictive drug. It is the most common recreational drug that is used mainly by men. Research has found that men who smoke marijuana more than once a week for 3 months have reduced sperm concentration and sperm count. Further studies have found that marijuana impacts sperm production, ultimately affecting the motility of the sperm cells.
Similar to marijuana, cocaine is also a highly addictive drug. A study found that men who used cocaine for 5 years or more have a strong association with low sperm concentration, reduced motility and increased proportion of abnormal morphology.
Cigarettes contain highly carcinogenic properties known to detrimentally affect male fertility. They harbour a significant quantity of reactive oxidative species (ROS), and elevated ROS levels in the body can subject sperm cells to oxidative stress, ultimately leading to impaired sperm function and a negative impact on male fertility.
Cigarettes also contain other hazardous substances such as cadmium and lead. Research has shown that exposure to these harmful agents can significantly reduce sperm count, motility, concentration, and morphology. Men are particularly vulnerable to such exposures, especially in industrial environments. Cadmium is an example of a heavy metal that has a direct impact on Leydig cells within the testicles; these cells are responsible for the production of testosterone under the control of luteinizing hormone. Therefore, increased smoking can negatively impact sperm production and ultimately male fertility.
Studies have found that there is a negative correlation between increased alcohol consumption and sperm production. Alcohol has been shown to interfere with the production of testosterone and impair Leydig cells. As a result, when a man is exposed to high levels of alcohol, sperm production is impaired. Research has also concluded that excessive alcohol intake for a long period of time can negatively impact the quality of semen and disrupt the levels of testosterone.
It should be noted that the threshold of alcohol intake that can negatively affect male fertility has not been defined. Additionally, the effect of alcohol is closely dependent on the amount of alcohol consumed.
What we eat and our weight can significantly influence our well-being, and research has revealed that an unhealthy diet can have adverse effects on men's fertility. Being overweight is typically defined as having a BMI (Body Mass Index) between 25 and 30 kg/m², while obesity is characterized by a BMI exceeding 30 kg/m². Studies have shown that men who are obese have a higher percentage of abnormal sperm morphology, increased DNA fragmentation and a higher risk of being infertile due to the association between sperm with high DNA fragmentation and high levels of ROS.
Interestingly, scientists have also found that men with high BMI have a reduced chance of achieving a live birth after receiving fertility treatment. Additionally, there is a negative correlation between paternal BMI and blastocyst development, meaning that the chances of an embryo reaching the blastocyst stage (a crucial stage in embryo development) are lower when paternal BMI is high.
The impact of lifestyle choices on male fertility varies amongst individuals however, a healthy diet can provide a great starting point to improve fertility before seeking professional assistance.
Damage to sperm from the lifestyle factors mentioned above is reversible so there is no need to worry! It usually takes approximately 90 days for the damages to be reversed. So instead of panicking, reduce or, if possible, abstain from such harmful factors.
It is essential to remember that male fertility is a complex interplay of numerous factors, some of which are unavoidable, but the disparity present within some of the factors discussed highlights the need for more research within the field. It should be noted that the cause of male infertility is unknown in approximately 50% of cases. Despite the advancements made in many assisted reproductive techniques and the extensive research in reproductive medicine, there are still many uncertainties that need to be addressed in order to support individuals and hopeful parents. Continued research and medical advancement will likely further our knowledge and enhance our ability to manage male fertility issues. At the end of the day, this is needed for the future – literally!