Sperm DNA fragmentation can be caused by a variety of factors, including illness, injury, lifestyle choices. This metric can be detected with a sperm DNA fragmentation test kit. Read on for our in-depth guide to sperm DNA fragmentation and how a sperm DNA fragmentation test kit can help.
This trend — higher levels of sperm DNA fragmentation correlating with lower live birth rates — holds true even for those being treated for infertility with in vitro fertilization (IVF).
In one study of 360 couples undergoing IVF, higher sperm DNA fragmentation levels were associated with lower fertilization rates, embryo quality, and pregnancy rates. The couples who were not able to achieve pregnancy had an average of 51.7% sperm with DNA fragmentation, as opposed to 39.5% in the pregnant couples. The researchers concluded that sperm DNA fragmentation “can predict ART [assisted reproductive technology] outcome.”
This study was especially valuable because, other than sperm DNA fragmentation results, there were few significant differences between the group that achieved clinical pregnancy and the group that didn’t. The sperm count, motility, semen volume, and other parameters were all basically equivalent between the two study groups. This suggests that sperm DNA fragmentation impacts fertility independently of other semen parameters.
In another study of IVF cycles, researchers found a significant negative correlation between DNA fragmentation index and live birth rate. Specifically, implantation rates (the percentage of embryos that implant into the uterine lining for pregnancy) were lower for couples in which the male partner had a DNA fragmentation index of 30% or above. Those couples had an implantation rate of just 11.7%, compared with the 22.6% for couples in which the male partner had a DNA fragmentation index of less than 30%.
The trend appears to hold across different types of fertility treatment. In a study of IUI (intrauterine insemination), IVF, and ICSI (intracytoplasmic sperm injection, a treatment in which a single sperm is injected directly into the egg), it was found that high DNA fragmentation index — defined as over 27% — had the power to predict whether or not a couple would achieve pregnancy. In this study, pregnancy rates for couples with high DNA fragmentation index were less than half that of low-DFI couples (14% vs. 29%).
While it’s not entirely clear that sperm DNA fragmentation causes recurrent pregnancy loss (defined as two or more consecutive miscarriages), research demonstrates that the two issues are correlated.
In one study, 45% of male partners in cases of recurrent pregnancy loss had high sperm DNA fragmentation levels, compared to just 15% of the control group. In another, couples experiencing recurrent miscarriage were more likely to have male partners with high rates of sperm DNA damage. Researchers concluded that the genetic integrity of sperm was a “significant predictor for future [miscarriage] and infertility.”
A sperm fragmentation test kit, along with a semen analysis, can help you gain a comprehensive understanding of your sperm health before trying to conceive.
Because of the many factors that contribute to the development of disease, it’s complicated to conduct research into specific causes. Some experts believe that “loss of sperm DNA integrity not only impacts reproductive and psychological health of the infertile couple but also increases childhood disease burden,” and that healthy sperm DNA is essential for “the health and well being of the next generation.” But the links are difficult to make conclusively.
A strong correlation has been found between the development of retinoblastoma, a childhood eye cancer, and DNA damage in paternal sperm. Researchers found that DNA fragmentation index levels were significantly higher in the sperm of fathers of children with retinoblastoma.
It’s also been shown that advanced paternal age has been associated with many conditions in offspring, possibly due to increased sperm DNA fragmentation with age. These conditions include:
During spermatogenesis (the sperm production process), the genetic material within sperm condenses. The DNA wraps around a few specific proteins to organize itself snugly in the sperm’s head. This allows large amounts of DNA to occupy a very small space, and may protect the DNA from damage.
But this process also has the potential to introduce damage. Firstly, it’s quite a large amount of genetic material that needs to be compacted tightly within the nucleus of the sperm. It’s possible that this twisting could cause physical breaks in the DNA.
Additionally, if there are problems with the mechanisms that package this genetic material, such as a lack of the proteins required to facilitate the condensation process, DNA will be more susceptible to damage from outside forces.
Free radicals, also known as reactive oxygen species (ROS), are unstable molecules produced as natural byproducts of daily life. At low levels, ROS are not typically damaging and may even be useful to cells. But if left unchecked, free radicals can cause damage to other molecules inside our cells, such as DNA. This damage is known as “oxidative stress.”
Our bodies typically use compounds called antioxidants to neutralize these molecules and prevent damage. Antioxidants are produced naturally by our body and absorbed from food or supplements. In fact, semen is known to contain relatively high quantities of antioxidants such as vitamin E, vitamin C, and glutathione, to protect sperm from oxidative stress. Antioxidants are also produced in other parts of the male reproductive system, including the epididymis, where sperm is stored.
There are certain experiences or behaviors that can cause levels of free radicals to rise beyond what our body can typically handle. Causes of oxidative stress include:
On the other hand, if levels of antioxidants are too low, possibly due to a poor diet, they won’t be able to adequately counteract free radicals.
Researchers believe that oxidative stress is the major cause of sperm DNA fragmentation. In research, it’s been shown that as oxidative stress increases, sperm exhibit elevated levels of DNA damage. At the highest levels of oxidative stress, high DNA fragmentation index can be observed alongside a loss of sperm motility.
Apoptosis is programmed cell death that’s part of normal growth and development. Think of it as a “self-cleaning” mechanism that eliminates unnecessary, damaged, or infected cells from the body. Though apoptosis involves the death of cells, it’s beneficial and important for the health of the overall organism. A cell that’s been marked for “deletion” can be identified by the presence of a specific protein, Fas, that induces apoptosis.
If the body is constantly cleaning out faulty cells, how do sperm cells with DNA damage make it into the semen? It seems that, sometimes, the body can recognize sperm with DNA damage and “earmark” them with Fas, but the process gets interrupted somewhere along the way, and damaged sperm are able to escape. This is known as abortive apoptosis.
Why this happens is not entirely clear, but we know it has an impact on fertility. In one study, men with abnormal sperm parameters display higher levels of Fas on their sperm.
These mechanisms are interrelated. It’s likely that, as opposed to a single one of these processes causing sperm DNA fragmentation, it’s a series of failures that results in high levels of DNA damage.
For example, if the DNA within sperm is not packaged correctly, it’s more vulnerable to oxidative stress. Too-low levels of antioxidants allow oxidative stress to damage sperm, and finally, the body fails to completely eliminate these damaged cells.