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‧ A new study found men are likely to have lower sperm counts than 50 years ago.
‧ The reason? Experts say it’s hard to tell but may be due to environmental exposures, chemicals or changes in weight.
‧ Being healthy overall is important for reproductive health, experts said. Men should talk to their doctor if they’re concerned about their sperm count.
Sperm counts and concentration are down all over the world, according to a new study that updates previous research and raises questions about exposures and men’s health.
From 1973 to 2000, sperm counts dropped by 1.2% per year, “which is a lot,” said Hagai Levine, who helped lead the research. From 2000 to 2018, the decline was 2.6% per year, “which is an amazing pace.”
The United States is part of this larger trend.
“In the U.S., due to availability of good data, we have the highest certainty that there is a strong and sustainable decline, but it’s similar globally,” Levine said.
It’s unclear why sperm counts have been falling.
“We don’t understand why we’re seeing this pattern, so I think it’s hard to be alarmist for an individual,” said Dr. Michael Eisenberg, a urologist focused on male fertility and sexual function at Stanford University and Stanford Health Care in California. He was not involved in the new study.
“But at a policy level, this should be a wake-up call to try and understand,” Eisenberg said.
Experts say falling sperm counts might mean it takes longer to have children. Here’s what to know.
What’s the evidence?
The new study is a meta-analysis, which means it combined findings from more than 250 previous studies. It also updates a previous meta-analysis the team published in 2017, adding data on sperm counts from 2011 to 2018 and regions in South America, Asia and Africa, where data had been incomplete before.
Men in the global south have seen the same significant decline in sperm count and concentration as the team showed in 2017 among men in North America, Europe and Australia, whose sperm counts and concentrations continued to fall, according to the new study.
Sperm count is a imperfect measure of fertility, but there is a threshold below which a low sperm count affects the chances of reproduction. On a population level, the study suggests that median sperm counts have dropped from 104 to 49 million per milliliter over five decades.
That means more men are likely to have sperm counts below the fertility threshold than was the case 50 years ago, said Levine, an epidemiologist and public health physician at the Braun School of Public Health, at Hadassah University Medical Center.
What’s the impact on fertility?
But Amy Sparks, a reproductive physiologist at the University of Iowa, who was not involved in the research, cautioned that sperm counts are falling, but not enough to affect the human population.
The paper is not “suggesting that our sperm concentrations are crashing at a rate that is going to lead us out to every man needing to walk into an infertility center. Heavens to Betsy, no.”
People have raised questions about sperm counts for generations. Sparks said she found a 1974 study of 390 men at the University of Iowa that raised concerns about low sperm counts.
“We can’t ignore that things are changing. Lifestyles have changed. Dietary patterns certainly have changed,” she said. “Through these changes, we are exposing our body to altered conditions. In response to those altered conditions, we’re seeing a decrease in sperm concentration.”
Levine, however, sees the drop in sperm count as a problem for today’s families, not just future ones.
Although most American couples can manage to have the one or two children they want, it may take them longer now than in the past. In Israel, some religious families want 10 or more children. Slower fertility may mean they run out of time before they can have that many, he said.
It’s challenging to study sperm counts and fertility is even harder, said Dr. Bruce Redmon, a professor at the University of Minnesota Medical School, who was not involved in the research but studies male reproductive disorders.
It’s not really feasible, he said, to sample sperm in a randomly selected population of men every year for decades. And men who seek help for fertility problems are not reflective of the entire population.
But overall, Redmon said, the new study was a reasonable way to look at the issue.
“It’s probably something we have to continue to take seriously and look at,” he said.
Why are sperm counts falling?
Studies haven’t yet explained why sperm counts are falling, but Levine has a few ideas.
Total sperm capacity is determined during fetal development, so exposures to human-made chemicals, stress and poor diet during pregnancy might all be contributing factors, Levine said.
Environmental exposures of the father before conception may also be related to poor fetal outcomes. In a man’s adult life, his sperm count can also be reduced by exposure to pesticides, lack of physical activity, poor diet, smoking and obesity, he said.
Excess weight changes hormone levels, adding more estrogen to the male body, Sparks said. And extra fat around male reproductive organs could increase heat there, which will decrease sperm production.
Sparks doesn’t think any one thing is causing the drop. It’s happening too fast to blame on reproductive technologies. But the world’s population is carrying more weight, spending more time spent sitting at a computer, eating more processed foods and packing those food in plastic. Any or all of those could be driving the drop in sperm count, she said.
“We need to be motivated to invest in the research to work on this,” she said. “It points to a need.”
What can men do to boost their sperm count?
Men concerned about their fertility should to talk to their doctor, Eisenberg said. It’s important to be evaluated and determine whether there are specific treatments that may help.
Being healthy overall is important for reproductive health. Eisenberg suggests a healthy diet, regular exercise and smoking cessation.
“I always tell men there’s a strong link between fertility and health, so anything that’s good for your heart is good for fertility,” Eisenberg said.
A few other tips:
►Alcohol use: Moderate alcohol use is OK, Eisenberg noted, with studies suggesting that semen quality drops only after about 20 drinks a week.
►Avoid extreme heat: There’s no strong link between what kind of underwear men wear – boxers or briefs. But heat exposure isn’t good, so he advises avoiding hot tubs and saunas while trying to conceive.
►Taking testosterone: He also discourages his patients from using testosterone, which has been tested as a contraceptive, because it reduces sperm production.