When research published in Human Reproduction Update noted that sperm counts have steadily declined between 1973 and 2011, with the average decline being around 53%, the results alarmed many writers, scientists, and doctors. The study, which was a meta-analysis (basically, meta-analysis is a type of research that compiles the statistical data of many other studies and looks for trends) created something of a media sensation, even leading GQ to publish a popular article titled Sperm Count Zero. GQ interviewed Hagai Levine, the researcher who led the meta-analysis; Levine said: “…we should hope for the best and prepare for the worst… that is the possibility that we will become extinct.”
If the trend continues, some worried, this could mean the end of humanity as we know it. But, are sperm counts really decreasing so dramatically? Should you be worried about your sperm? And what can you do to protect your sperm?
First, let’s take a look at what doctors consider to be a “normal” sperm count. Doctors determine a man’s sperm count by performing what is known as a semen analysis. A semen analysis lets a doctor determine important factors of sperm health, like sperm count, sperm motility (how well sperm move), and sperm morphology (how “normal” the sperm look). According to the Handbook of Fertility, about 20 million sperm per milliliter is considered normal. Normal motility or movement is characterized as 50% or more of the sperm being able to move forward. According to the Journal of Human Reproductive Sciences, approximately 2% of men have sperm parameters that are below what is characterized as normal.
Does having a low sperm count alone mean that you’ll have trouble conceiving? The Handbook of Fertility notes: the more fertile the female partner, the less sperm will be needed to conceive. The Handbook of Fertility further notes that without proper uterine function, even high sperm counts won’t result in conception. You need sperm, an egg, and a healthy uterus to conceive. So, it is important to take into account both partners’ fertility when looking at issues of infertility. Low sperm counts alone don’t result in infertility.
That said, a 52% reduction in sperm counts is alarming news. Should we be worried? Julia Belluz, a writer for Vox investigated and offered some reassurance. For one, in the article, she notes that sperm counts can differ greatly from sample to sample. Lifestyle choices made in the months prior to the sperm analysis can have an impact on sperm count. For example, Daily Wellness has written about how lifestyle factors, like wearing tight-fitting jeans, using the hot tub, or using a laptop on your lap can reduce sperm count. Excess heat can kill sperm. Fortunately, because sperm mature in the testicles in roughly 2 to 3-month cycles, many men who change these behaviors can see their sperm counts increase. Belluz also notes that the researchers in the meta-analysis published in Human Reproduction Update only looked at semen analysis taken after masturbation and only at results that used a hemocytometer (a fancy name for a type of sperm counting device used by doctors) to evaluate semen counts. The meta-analysis also included some older studies, which may have included “unmeasured variables, that influenced the results.” Basically, what this means is that there may be hidden reasons why the sperm counts trended lower. Other good news for men is that, anecdotally, fertility doctors haven’t noticed a larger than average number of men showing up in their offices with low sperm counts, which also indicates that the warnings about the end of humanity as we know it may be a little premature. Ultimately, to really show compelling evidence that sperm counts are truly declining as quickly as the meta-analysis suggests, researchers would have to perform a long-term study on men, evaluating their sperm counts over time. Unlike the research we have now, that looks backward (retrospectively), the research would need to look forward, measuring men’s sperm regularly, and looking for trends over time. The population studied would have to be sufficiently large enough to produce meaningful results.
Researchers writing in Physiological Reviews also noted issues with other studies that indicated that sperm has declined by over 50% over the last 50 years. Some concerns the researchers noted included poor data sources, variable data sources, issues with statistics used in analysis, bias due to the fact that the studies were looking at different populations, and other confounding factors like the age of people from whom the samples were drawn and inability to control for the time period between ejaculation. All of this means that there might be issues with some of the data. That said, the researchers did acknowledge that as many as 20-30% of young men may have sperm concentration factors that put them at risk of lowered fertility. Despite some issues with the research, there is reason to believe that sperm counts may be declining.
The meta-analysis published in Human Reproduction Update along with the results of other studies are compelling enough to suggest that something may be going on with sperm counts and testicular health, and other studies indicate that lifestyle factors, exposure to chemicals and endocrine disruptors, and diet may be affecting testicular health and sperm counts in ways that men should consider.
Research published in the Journal of Fertility and Sterility suggested that chemical exposure and Western men’s sedentary lifestyle may be a factor that could account for reduced sperm counts (it is important to note that the meta-analysis didn’t see declining sperm counts in non-western men). The study published in Fertility and Sterility looked only at sperm donors to track declining sperm counts and noted a decline. The researchers wrote: “We demonstrated a time-related decline in semen quality. Given that donors have higher than average sperm counts, these trends would likely be magnified in the general population.” Interestingly, New Yorkers in the study didn’t see declining sperm quality. The Atlantic magazine spoke to Peter Schlegel, the president of the ASRM, and a doctor at Weill Cornell Medical Center, who noted that New Yorkers tend to be more physically active than the general American population and that New York’s water quality is rated among the highest in the U.S.
What does this all mean? Men who want to keep their sperm quality high should exercise, avoid sitting around, and drink clean water. What is it about the water that could be impacting sperm quality?
Some researchers believe that endocrine disruptors, or chemicals that imitate natural hormones, might be to blame. It is believed that endocrine disruptors could change the functioning of the endocrine system and have effects on fertility. While the research isn’t conclusive (more studies need to be done), researchers writing in the Asian Journal of Andrology note that some pesticides, PCBs, and DDT may be affecting fertility and are being investigated as potential contributors to testicular and prostate cancers, abnormal sexual development, undescended testicles, chronic inflammation, and infertility, among others. Researchers writing in Physiological Reviews note that fertility rates have been declining, and they also note increases in other conditions including testicular cancer, sex development disorders, low testosterone levels, low semen quality, and more. It is believed that many of these problems arise in the fetus and may be the result of environmental exposure, particularly to certain types of chemicals. For example, certain pesticides and fungicides can impair masculine development in the womb. Additionally, low testosterone levels were linked to obesity and smoking.
Research published in Scientific Reports found that phthalates could have an impact on semen quality in both human and dog sperm. Phthalates are chemicals found in everything from toys to food packaging to pharmaceutical products. They are found in shampoos, hair sprays, cosmetics, and aftershave lotions.
How can you avoid your exposure to phthalates? Read cosmetics labels, especially detergents, hair spray, and perfume products to see if the products contain phthalates; unfortunately, companies aren’t required to disclose phthalates so the only way consumers can tell if there’s phthalates in their cosmetics is to see if the ingredients list includes the word “fragrance.” Consumers can also avoid brands that contain phthalates by referring to the FDA’s chart: 2010 Survey of Cosmetics for Phthalate Content (hint: scroll to the bottom of the page to find the chart and see if your favorite brands are listed).
Another way to reduce exposure is to avoid drinking out of plastic cups and to wash your hands frequently. In a study published in Science of the Total Environment, researchers found that children who washed their hands and who avoided drinking water from plastic cups had less phthalates in their urine.
It appears that environmental factors, like exposure to certain chemicals and pesticides, and certain lifestyle factors can impact sperm quality and sperm count. While further investigation needs to be done on whether sperm counts are in fact decreasing, early indications suggest that men can take the following steps to keep their sperm counts up:
- Maintain a Healthy Weight
- Avoid Hot Tubs, Saunas, Hot Baths, Using Laptops on Your Lap and Tight Clothing
- Quit Smoking
- Choose organic produce when possible and avoid produce known to be high in pesticides
- When possible, reduce exposure to endocrine disruptors
These are just some things men can do in the short term to keep sperm counts healthy and high. Ultimately, we’ll have to wait on longitudinal studies to learn more about how serious the decreasing sperm count problem is, and also wait on further research to determine what environmental and lifestyle factors might be specifically contributing to this issue.