Sperm Quality Declines At Age 30

Advanced paternal age increases the chances of infertility, as well as the risk of autism, schizophrenia, and bipolar disorder.

Last week this post on X garnered about 16.7 millions views. Why? Likely because it brought up something rarely discussed: once a man hits 30 years-old, the quality of his sperm declines and waiting to have children, as Pico Paco later explains, is not a great idea. I was truly fascinated by the engagement.¹

Most boys and young men have never been taught, for some reason, that the quality of their sperm declines over time. The longer they wait to have kids, the more likely they are to experience infertility, pass on genetic mutations, and other issues. In fact, advanced paternal age has been strongly associated with a higher incidence of autism, schizophrenia, and bipolar disorder.

When we learn that couples are struggling with infertility, we often assume (wrongly) that the issue lies with the wife, when, in reality, the problem could very well be with the quality of the husband’s sperm, according to research.

Fact: Peak sperm health for men is between the age of 18-30.

Men should not delay fatherhood due to the decline in sperm quality over time, it's crucial to highlight the significant increase in paternal mutations as men age. According to research in journal Nature, the number of de novo mutations in sperm increases notably with paternal age. De novo are genetic changes that occur for the first time in an individual, rather than being inherited from either parent. Specifically, a man who becomes a father at 30 will introduce 50% more mutations into his child's genome compared to if he had fathered the child at 18.

The study in Nature shows that the number of de novo mutations in children is significantly influenced by the father's age. The study found that mutations from fathers increase by approximately 1.51 per year of paternal age, far outpacing the rate at which maternal mutations accumulate. This pattern suggests that delaying fatherhood contributes to a higher mutational burden in offspring, which could increase the risk for various genetic disorders, including neurodevelopmental issues like autism and schizophrenia.

Adding to this, recent studies emphasize that as men age, not only do the mutations in sperm increase, but the DNA in sperm also becomes more prone to damage, which may not be entirely repaired during fertilization. This can result in a higher likelihood of passing on genetic abnormalities to the offspring. The cumulative effect of these mutations and DNA damages underscores the potential risks associated with delayed fatherhood.

Moreover, these findings are supported by data indicating that a significant portion of genetic disorders linked to paternal age arises from these mutations. The argument is not merely theoretical; it is backed by robust evidence showing the biological mechanisms that deteriorate with age, leading to increased risks for the offspring.

Given this information, the case for early fatherhood becomes not just a matter of personal choice but also one of genetic responsibility, some argue. While there are certainly sociological factors that might mitigate these risks to some extent, the biological risks associated with delayed fatherhood should not be overlooked.

What The Data Says

The article "Effects of increased paternal age on sperm quality, reproductive outcome and associated epigenetic risks to offspring" explores the growing trend of delayed fatherhood and its consequences. As societal norms shift, more men are choosing to have children later in life, a decision often influenced by factors like longer life expectancy, career priorities, and the widespread use of contraception. However, this delay is not without significant consequences, particularly concerning male fertility, sperm quality, and the health of offspring.

Decline in Sperm Quality and Reproductive Hormones

The article begins by examining how advancing paternal age affects testicular function and reproductive hormones. As men age, there is a notable decline in testicular volume, largely due to the reduction in the number of Sertoli cells, which are essential for sperm production. Studies have shown that men over 75 have, on average, 31% smaller testicular volume compared to those aged 18-40. Additionally, the number of Leydig cells, responsible for testosterone production, also decreases significantly with age, leading to lower testosterone levels. This hormonal imbalance contributes to symptoms commonly associated with andropause, such as reduced libido, fatigue, and cognitive decline. The reduction in testosterone further impacts sexual function and frequency, compounding the challenges of conception for older men.

Deterioration in Sperm Parameters

The article also highlights the deterioration in key sperm parameters with advancing paternal age. Research has shown that semen volume, sperm motility, and the percentage of normal sperm morphology tend to decline as men age. For instance, a significant decrease in sperm quality is observed after the age of 35, with sperm motility and semen volume notably declining by the ages of 43 and 45, respectively. These declines directly impact the likelihood of conception, as older men exhibit lower semen quality and reduced chances of successful fertilization.

Increased DNA Fragmentation and Genetic Mutations

One of the most critical aspects discussed is the increase in DNA fragmentation and genetic mutations in sperm as men age. DNA fragmentation, which refers to the breaking of DNA strands, is a significant factor in male infertility and is strongly associated with advanced paternal age. Studies have shown that men over 45 have twice the level of DNA fragmentation compared to those under 30, which significantly reduces the probability of conception and increases the risk of miscarriage and other reproductive failures. Additionally, the continuous division of sperm cells throughout a man's life increases the likelihood of de novo mutations, which can lead to serious genetic disorders in offspring.

Epigenetic Risks and Long-term Health Impacts on Offspring

The article also explores the epigenetic risks associated with advanced paternal age. Epigenetics involves changes in gene expression that do not alter the DNA sequence but can be influenced by environmental factors and age. As men age, the likelihood of epigenetic abnormalities in their sperm increases, potentially leading to various congenital disorders and long-term health issues in their children. For example, advanced paternal age has been linked to an increased risk of disorders such as autism, schizophrenia, bipolar disorder, and childhood leukemia. These conditions are believed to arise from both genetic mutations and epigenetic alterations in sperm, which can disrupt normal development.

Health Risks to Offspring: Autism, Schizophrenia, and Bipolar Disorder

One of the most alarming findings discussed in the article is the increased risk of neurodevelopmental disorders in children born to older fathers. Advanced paternal age has been strongly associated with a higher incidence of autism, schizophrenia, and bipolar disorder. For instance, children born to fathers over 50 are nearly six times more likely to be diagnosed with autism compared to those born to fathers under 30. Similarly, the risk of schizophrenia and bipolar disorder also increases significantly with paternal age. These risks are thought to stem from the accumulation of genetic mutations and epigenetic alterations in older sperm.

Preterm Birth, Low Birth Weight, and Other Pregnancy Complications

The article also highlights the increased risk of adverse pregnancy outcomes associated with advanced paternal age. Men over 45 are more likely to father children who are born prematurely or with low birth weight, conditions that are linked to long-term health problems such as attention deficit hyperactivity disorder (ADHD), cerebral palsy, and chronic lung disease. Additionally, the risk of stillbirth and spontaneous abortion increases with paternal age, further complicating the reproductive outcomes for older men.

Conclusion: The Need for Awareness and Counseling

In conclusion, the article underscores the importance of raising awareness about the risks associated with delayed fatherhood. As more men choose to have children later in life, it becomes increasingly important for healthcare providers to counsel prospective fathers about the potential impacts of advanced paternal age on fertility and the health of their offspring. The article calls for further research to better understand the molecular mechanisms behind these effects and to develop more effective diagnostic and therapeutic tools to address the challenges of male reproductive aging.

Bottom line: We need to stop raising boys to think that their sperm is invincible and that they can wait to have children without increasing health risks for their future children. The belief that they can prioritize traveling, brunches, careerism, etc., without consequences must be challenged with facts. Culture has changed but biology has not.

More Sources:

• Jónsson et al., Nature (2017) for the data on paternal mutations.

• Gao et al., Human Reproduction (2024) for the relationship between paternal age and de novo mutations​

1. I majored in biological sciences at Clemson University and had a brief stint as a pharmaceutical chemist before switching gears to theology. So, every now and then, I like to let my inner science nerd out for a little fun!