Declining Male Fertility -- Urban Myth Or Alarming Trend?

Medically Reviewed by Gary D. Vogin, MD
From the WebMD Archives

July 24, 2000 -- Are sperm count and quality going downhill in modern man? That question has been haunting scientists and prospective parents since 1992, when a Danish study found that sperm count in Western European men has been declining for the last 50 years. Since that time, numerous other studies have come out, some supporting and some debunking the theory -- but all creating fodder for the fertile debate.

"We don't have any evidence that male infertility is increasing," Larry Lipshultz, MD, tells WebMD. "I think what is happening is that more people are going to doctors for infertility because most couples are delaying having kids and they are presenting with problems ... but I don't think we have any reason to think that the incidence is increasing." Lipshultz is a professor of urology at Baylor College of Medicine in Houston.

Concerning study results, Lipshultz says that just as many show that fertility is going down as show that it is not changing or going up. "So there is no final answer [to the question] 'Are sperm counts decreasing?' It is very controversial."

Other fertility and reproductive experts agree. "There are conflicting reports. It is very difficult to obtain information under controlled conditions ... in order to tell precisely that this is happening and to what degree this might be happening," Panayiotis Zavos, PhD, tells WebMD, referring to some of the limitations in collecting data these studies have.

"We continue to see more and more infertility and probably younger people come into our fertility center seeking assistance," he says. "But [is it] an epidemiological trend that the qualitative and quantitative measurements of sperm are deteriorating, or is it because people are coming out of the closet and seeking more assistance?" Zavos, professor of reproductive physiology and andrology at the University of Kentucky in Lexington, is both the director of the Andrology Institute of America and the associate director of the Kentucky Center for Reproductive Medicine and In Vitro Fertilization.

"I am afraid the jury, from a scientific point of view, is still out. There are some data that show that some populations have declining counts, whereas other data are unable to find it," says Kevin Lindsay, PhD, a principal clinical scientist in reproductive biology at Hammersmith Hospital in London. "I am sitting on the fence; I can see evidence both ways. It is something that we need to be aware of and keep an eye on. We need further studies because if decline is real, we may need to be concerned about it."

Some scientists however are not sitting on the fence. In the most recent issue of the International Journal of Andrology,there are no less than four articles on the topic of declining fertility -- two supporting the idea, two refuting it. Many who support the idea of declining sperm count place the blame on environmental factors, including an increase in what is referred to as endocrine disruptors.

An endocrine disruptor is a natural or synthetic substance that disrupts some aspect of the endocrine system, which governs our hormones. It can be a prescription drug, a naturally occurring chemical, or an industrial or environmental pollutant.

The endocrine disruptors that concern some scientists most are those that have an estrogen-like effect, meaning that they can attach themselves to estrogen receptors in the body and cause different and unknown effects, including hormonal imbalances.

A lot of chemical pollutants may get into the body during a lifetime of eating and drinking polluted or contaminated water, says Joshua Barzilay, MD. "A lot of the chemicals that are in the water do have an estrogen-like effect," says Barzilay, who is an endocrinologist at Kaiser Permanente of Georgia, and also author of the book The Water We Drink.

Barzilay says that many of the worrisome endocrine disruptors are chemicals that result from the breakdown of items that have made our lives easier in the last 25 years, such as plastics and computer chips. And while they are not terribly poisonous per se, the molecules take a long time to break down, and they are accumulated in our bodies and stored in places such as fat tissue.

Drinking bottled water won't help either, says Barzilay. "It is not just the water itself: it is the fish that live in the water, the animals that we eat that drink from the water," he says, adding that it is also the incineration of items, such as plastics, that then return to the water via precipitation.

"It is all interconnected, one with the other."

These endocrine disruptors are of concern not only because they enter a person's body but also because they can alter the development of a growing fetus. "The development of the fetus in utero is in part governed by the estrogen and testosterone environment," says Barzilay. "A lot of these chemicals are released into the bloodstream during gestation, and they have an estrogen-like effect and may suppress development of testicles in utero."

Suppressing the development of testicles in utero could lead to infertility 20 years down the road. It also could lead to other problems, such as testicular cancer and hypospadias, a small but correctable malformation of the penis, both of which have been on the rise.

Barzilay says studies have found behavioral and physiological abnormalities in animals exposed in utero to too much estrogen at the wrong time. "But to do studies like that in humans is kind of tough," and even if researchers found the same effect, they may not be able to prove estrogen exposure was the cause.

Lindsay agrees that this argument is plausible, but he isn't convinced that is what is going on. "You can take small bits of hard data and you can try to link them all together into a global idea -- that is where the science begins to break down," he says. "It is very easy to overinterpret some of the harder science -- some of which has given us declining sperm counts, some not. So then coming up with a theory of why there might be declining sperm counts, you might argue, is premature because we haven't even shown that they are."

Lindsay says there are factors that could skew study results, such as the fact that couples are delaying starting a family -- which everyone agrees does affect fertility. There may even be other factors that we may not be aware of -- for example, some of the studies that found declining sperm counts were done in cities.

"People in cities sit down more. That may be a very silly thing, but we know from testicular physiology that testes are meant to be cool, that is why they hang in a little sac outside the body. And we know that if you raise temperature that you can disrupt sperm counts," he says. "Now whether in practice the fact that men wear trousers, they sit down in offices on their testes and keep them warm eight hours a day is enough to cause declining counts, nobody knows."

Other critiques of the studies are the methods used of collecting and analyzing sperm, which may have been different 50 years ago compared to today, says Lindsay, making it like comparing "kilograms to pounds." Additionally, the men who are included in studies, because either they show up at a fertility clinic or agree to be tested, may also skew the results.

"Here we run a fertility service. Now the problem with our database is, of course, the fact that people come to us at all means that they are complaining of fertility problems. So they are a self-selected group," he says. "Getting normal men is quite difficult; there is even the argument that when you are recruiting people, people who are prepared to be recruited don't represent the average."

"The bottom line is that there are some unanswered questions that need to be addressed," says Lipshultz. "But we don't have any data to really say that the incidence increasing. What is increasing is the awareness and the public's desire to get treated."

Some large studies are underway, including one by the World Health Organization (WHO) and another by the Environmental Protection Agency, but results may be years away.

"It is difficult to study global problems without having a total commitment from the various governments and agencies. The WHO is involved, but not that actively involved, and nobody has addressed this issue as aggressively as they need to do it," says Zavos. "More organized studies worldwide should be initiated looking at that question because it is a serious problem, if indeed it is happening, and we don't know about it. They are very serious matters that affect humanity."