Sperm quality refers to sperm’s ability to accomplish fertilization. This ability is impacted by two, interconnected factors: sperm motility and sperm morphology, as well as by the health of the DNA carried by the sperm.
Motility refers to the ability of the sperm to move or “swim,” which is essential for them to move through the female reproductive system and fertilize the egg. Progressive motility is the best type of movement that can be seen in sperm testing—that means the sperm move forward in straight lines or in large circles, as opposed to in small tight circles or along erratic paths.
Morphology means the sperm’s structure or shape, which is ideally:
This shape is important because it impacts a sperm’s ability to travel to and penetrate and fertilize an egg.
Each sperm cell contains 23 chromosomes, or molecules of DNA, the material that guides the growth and development of the entire human body. This is half the number of chromosomes in a typical human cell; sperm cells are known as “haploid” cells. The egg contains the other half. Together, they create a fully realized cell of 46 chromosomes (known as a “diploid” cell), which then divides to become all of the other cells in the body.
The other half of the sperm equation is sperm quantity, or sperm count/concentration. Sperm count is the total number of sperm in a particular quantity of semen, the fluid that carries sperm out of the penis. Sperm concentration refers to how densely packed those sperm are within the semen. For example, a sample may include 3 milliliters of semen and a total sperm count of 45 million; that would be a concentration of 15 million sperm per mL.
Sperm quantity and sperm quality are separate factors; a high sperm count isn’t entirely helpful to fertility if most of those sperm are misshapen, can’t swim properly, or carry damaged DNA. But sperm quality issues and low sperm count can be caused by some of the same things, including exposure to toxins or chemotherapy, smoking, and hormone imbalance
These are just a few of the most common factors affecting sperm quality:
As a person ages, their sperm motility decreases (according to one study, on average about .8% per year). Additionally, they’ll have lower numbers of sperm with normal morphology—research indicates that normal sperm morphology declines .2–.9% per year, resulting in a 4–18% decrease in normal morphology over a 20-year period. And finally, the sperm of older people is more likely to have higher rates of DNA fragmentation, as well as additional genetic mutations that can lead to schizophrenia, autism, and more. The best way to prevent the issues associated with aging sperm is to freeze your sperm at a younger age. Learn more about sperm freezing.
A balanced, Mediterranean-style diet rich in fruits, vegetables, fish, and nuts—and low in soy products, processed meats, and trans fats—is associated with improved sperm quality.
Alcohol can dampen testosterone production, and negatively affects all aspects of your sperm such as count, concentration, and morphology. Smoking can be especially bad for sperm morphology, creating genetic defects that lower sperm quality. Learn more about smoking and sperm health.
Chronic sleep deprivation (less than 6 hours a night) reduces testosterone levels, lowers sperm count and motility, and increases levels of anti-sperm antibodies, further damaging your sperm. Learn more about sleep and male fertility.
Examples include testosterone, anabolic steroids, SSRIs, chemotherapy drugs, opiates, NSAIDs, and any other medication that has an impact on sperm quality.
Many supplements are associated with improved sperm quality, sperm count, and testosterone production. Learn more about male fertility supplements.