Male Fertility
The Scoop on Male Fertility: New Science Shows It’s Not Just About Age
An Interview with Dr. Paul Turek
Future Family  |  Mar 28, 2018

We tend to focus our energy on women's biological clocks. But men–who are also choosing to start their families later–also have a biological clock that affects their fertility. Even though men can produce children into their 80s, their sperm changes over time, which could have enormous implications on their family planning. Should men focus as much energy on freezing their sperm as women are on freezing their eggs?


To get the scoop on men’s fertility, we recently sat down with Dr. Paul Turek, an internationally-renowned doctor in men’s reproductive and sexual healthcare, a researcher and a Medical Advisor at Future Family.


FF: Do men have a biological clock?

The aging for men happens in the quality control machinery that makes sperm. It’s not chromosomal issues, but mutations, which are little tiny dings in the DNA that can cause problems in fertility.


Dr. Turek: Yes! It's not the same as a woman’s clock, though. It’s slower. The production of eggs and sperm is different, so each ages in a different way. Women are born with all their eggs, which slowly change as they get older.  Time and the environment take a toll on eggs and can mess them up chromosomally. Men make new sperm all the time until the eighth decade. The aging for men happens in the quality control machinery that makes sperm. It’s not chromosomal issues, but mutations, which are little tiny dings in the DNA that can cause problems in fertility. There is a gradual decline in the ability to conceive. The clock doesn't stop; the clock slowly winds down.


FF: What specifically happens to men’s sperm as they age?


Dr. Turek: The purposeful motion of sperm, or what we call motility, slows down. Motility will fall one percent per year after 40. The real significant changes for fertility decline are erectile dysfunction, sex drive, overall health, and whether you’re healthy enough to have sex.


FF: What about DNA mutations?


Research, which is still coming together, tells us that as men age, their sperm carry more mutations than women’s eggs–about tenfold more. It goes up 10 percent per decade up to 60 to 70 years old. Those mutations are evolution–that's how we change. They can be handed down to offspring. A lot of these mutations can cause disease and some of them go unnoticed. These mutations generally don't cause infertility in fathers because they are not as large a problem as chromosome issues in eggs. For guys, the mutations they hand down are concentrated in the neurodevelopmental genes and suggests that we are evolving as a species from a neurodevelopmental perspective. But that also means that we may be looking at greater prevalence of autism, schizophrenia, bipolar disorder and dyslexia in future generations.


FF: Is it true that there are also epigenetic changes to the sperm that occur because of a man’s lifestyle choices?

A recent study that looked a group of men’s sperm at two ages, young and older, found dramatic epigenetic alterations.


Dr. Turek: Yes. Epigenetics is the other change that occurs in men’s sperm with age. It's basically a mechanism for how the environment interacts with genes. It’s the little marks on the DNA that keep genes from expressing themselves or allows them to express themselves. Age and the environment change the epigenetics of sperm. A recent study that looked a group of men’s sperm at two ages, young and older, found dramatic epigenetic alterations. We think that some of these changes are directly male age-related and others are influenced by diet, health, toxins (pot, tobacco, alcohol etc). In other words, they are modifiable changes. In the future, the epigenetics of infertility may allow us to pinpoint exactly what environmental issues are influencing these changes.


FF: How can a guy test his fertility?

To know the most about your fertility, you would want to have a physical exam in addition to a sperm analysis (the sperm count) and a good medical history.


Dr. Turek: The single best measure of fertility potential is actual fertility, more than the sperm count (unless it’s zero; and even then a second opinion is important). Sperm counts do matter but they can vary widely in an individual, from day-to-day, season-to-season and year-to-year. To know the most about your fertility, you would want to have a physical exam in addition to a sperm analysis (the sperm count) and a good medical history. But it’s important to know that your lifestyle and the way you treat your body has far more impact on your fertility than what a semen analysis lets you know.


FF:  Based on this new knowledge, should all men start thinking about freezing their sperm at 40?


Dr. Turek:  It's really a very personal decision. I’d say it depends on your circumstance and how risk averse you are. If you’re not wedded to the idea of having kids with someone until you are 40, that's the age to start thinking about it. I think 60 is too late as a lot of the genetic changes to sperm have already occurred by this age. Most men don't mind freezing their sperm because it's less invasive than, say, freezing eggs.  It's not romantic making love to a paper cup, but it's not as psychologically as stressful as a blood draw! The three main groups who should think about it are: men of advanced paternal age, those who have cancer or an autoimmune disease that may require chemotherapy or surgical treatment, and those who have a high risk lifestyle such as military service. The military recommends you freeze sperm before deployment.


Dr. Paul Turek is a Medical Advisor at Future Family, a leading authority on male fertility, and an advisor to the NIH, the CDC, the White House, and Men’s Health Network among others. Dr. Turek is founder and director of The Turek Clinics and previously Professor and Endowed Chair at UCSF. Click here to learn more about Future Family’s Sperm Activity Test.

More articles for you