Scientists Say Older Dads Pass More Genetic Problems to Their Kids

Scientists have revealed that as men age, their reproductive cells (sperm) undergo genetic changes that may affect the health of their future children.

The study, conducted by scientists in the United Kingdom and published in Nature, examined over 100,000 sperm samples from 81 healthy men aged between 24 and 75. The researchers discovered that with increasing age, sperm accumulate “DNA mutations,” some of which are linked to genetic disorders and inherited diseases.

According to the study:

• Ages 26–42: Around 2% of sperm carry disease-causing mutations.
• Ages 43–58: The rate increased to 3%.
• Ages 59–74: It rose further to about 5%.
• At age 70: Around 4.5% of sperm carried harmful genetic variations.

The researchers found that these mutations accumulate at an average rate of 1.67 mutations per year and that sperm health begins to decline noticeably after the age of 43.

Professor Matt Hurles, Director of the Wellcome Sanger Institute and co-author of the study, stated:

Our findings reveal a hidden genetic risk that increases with paternal age. Some DNA changes not only survive within the testes but also expand, which means older fathers are more likely to pass harmful mutations to their children.

The study found that some mutations can make sperm cells more dominant, allowing them to outcompete healthy cells. These changes may increase the risk of genetic diseases, developmental disorders such as autism, and hereditary cancer syndromes in children.

Data shows that children born to fathers over 40 have a 51% higher risk of being diagnosed with autism compared to those born to fathers in their 30s.

Using advanced DNA sequencing technology capable of reading both strands of DNA, scientists identified over 40 genes where mutations made sperm stem cells “selfish,” allowing them to replicate faster and become more common with age.

Although such mutations occur in a small proportion of sperm, their impact is significant because they affect critical genes. Interestingly, lifestyle factors like smoking and alcohol consumption did not seem to influence these genetic changes, suggesting that the body naturally protects sperm from some environmental damage.