Sometimes, it feels like the correlation between age and fertility is drilled into women’s heads. We all know that female fertility declines with age, but what about men? Do they also have a biological clock they should be mindful of? If so, when are men most fertile and at what age do they begin to see a decline in fertility? We’re exploring those questions and more.
At what age are men most fertile?
Unlike women, who are born with a finite number of eggs, men continue to produce sperm throughout their life. They also regenerate their entire sperm supply, on average, every 64-74 days in a process called ‘spermatogenesis.’
Sperm isn’t necessarily a finite resource like eggs, but studies indicate that certain parameters like morphology (shape) and motility (the way it moves) decline as a man ages. The correlation between motility and morphology and age means that a man’s sperm at age 40 probably isn’t as healthy as it was at age 30.
Research on when sperm health and fertility decline in men is mixed. Some studies suggest a decline begins around age 35, while the Centers for Disease Control (CDC) reports significant decreases after age 40. Lifestyle factors also play a key role in sperm health, adding to individual variation.
In one study that looked at couples undergoing intrauterine insemination (IUI), men over the age of 35 had fertility rates of 25% compared to men under 35, who had fertility rates of 52%. Another study evaluated the relationship between age and semen parameters and concluded that male fertility decline begins at 35. It suggested that male fertility peaks between 30 and 35.
Although the exact age of male fertility decline is unclear, it's generally believed that fertility begins to decrease around age 35 and continues from there. Men are most fertile before this point, though the specific window of peak fertility remains undetermined.
That said, many men successfully conceive a child beyond this time, and many lifestyle factors can be optimized to support improved fertility.
How age affects male fertility
Age is among the most significant factors affecting a couple’s chance of conceiving and their pregnancy outcomes. Several factors are affected by age. For example, an older male may take longer to conceive and may have an increased risk of pregnancy loss.
So, why does age impact male fertility? It comes down to how aging affects the health of sperm. Sperm health can be measured with four key parameters: sperm count, motility, morphology, and sperm DNA fragmentation. The following sections share more about each of these sperm parameters.
Sperm count and concentration
Sperm count is the number of sperm produced per ejaculation. Some research indicates that sperm count decreases with age–though there is conflicting data that shows lower concentration in men as young as 26 years old. A normal count ranges from 15 to 200 million sperm per milliliter, but this can vary daily due to factors like diet, stress, and body temperature. A count below 15 million per milliliter is considered low.
Sperm motility
Sperm motility refers to how well sperm move. Higher sperm motility is beneficial, as sperm must be healthy and able to swim through the fallopian tubes to fertilize the egg. Some research suggests most men can expect sperm motility to decrease by about 0.8% per year. Another study compared the sperm of men between the ages of 30 and 35 with those of men over 55 and found that sperm motility decreased by 54%.
Sperm morphology
Morphology refers to the shape, size, and structure of sperm. Healthy sperm should have a smooth oval head with a cap, a midpiece, and a long tail. This allows sperm to swim toward an egg. All men may produce some abnormal sperm, but as men age, they tend to produce more abnormally shaped sperm.
Sperm DNA fragmentation
Sperm DNA fragmentation (SFD) refers to the amount of abnormal genetic material (damaged DNA) inside a sperm. The more normal sperm, the better the chances of conception, but research shows that sperm DNA fragmentation increases with age. Chronic inflammation and oxidative stress, as well as certain lifestyle choices like smoking, alcohol and poor diet, have also been shown to contribute to SDF.
How can men improve their fertility as they age?
Certain lifestyle choices significantly impact male fertility, especially as men age. For example, research shows that regular physical activity increases antioxidants, protecting sperm from damage. It also helps maintain a healthy weight, reducing the risk of obesity-related impacts on sperm count.
You can also adopt a sperm-healthy diet. A diet rich in fish like salmon and tuna may help with sperm count, with men who consume the most fish having a 65% higher sperm concentration. Omega-3 fatty acids in fish are key to supporting sperm production.
Below are lifestyle changes you can make to positively impact your fertility, regardless of age:
- Maintain a healthy weight
- Avoid smoking
- Limit diet drinks and other drinks that contain aspartame
- Limit alcohol consumption
- Avoid high temperatures on the testicles for extended periods of time
- Eat a balanced diet with plenty of antioxidant-rich foods
- Consider supplementation specifically designed to support sperm health
Do men ever stop producing sperm?
No, most healthy men never stop producing sperm. Men typically begin producing sperm around puberty and continue to produce sperm for the rest of their lives. However, Some research indicates a decline in sperm quality with age.
The bottom line
The relationship between age and male fertility may look different compared to women, but most research points to an age range when men are most fertile. Semen quality and male fertility naturally decline with age, but there are steps you can take to support sperm health over time. By making positive lifestyle changes, you can help protect and maintain fertility as you age.
