Older Men's Sperm are worse -- Freeze your sperm whilst young!

If you are genetically male and think that you might want to have children at any point in the future, it’s worth freezing a sample of your sperm now. It’s a low-cost way of increasing the chance your future children will be healthy.

Because men produce new sperm on a very regular basis, and mutations accumulate with age, sperm from older men will generally have more mutations than sperm from younger men. Interestingly, this is not true for women – while women face declining fertility and increased risk of various complications in their late 30s and 40s, their eggs have all been present since birth and thus have the same low number of mutations regardless of when they are used. The graph I’ve attached here shows the steadily increasing rate of mutations associated with paternal age. It implies that there’s a benefit to freezing sperm as early as possible and then using those frozen “young” sperm when it’s time to create children.

The topic of just how responsible these mutations are for increases in autism, ADHD, schizophrenia, and other disorders is being hotly debated right now. Many studies point to an increased risk with increased paternal age, but it’s really hard to disentangle other factors such as the fact that men who reproduce later in life are more likely to have older partners and are more likely to carry some autistic traits. This is one of those cases where the science is not fully decided, but there’s enough evidence indicating a risk that it’s worth having sperm frozen as a preventative measure.

---

Here are some links for further reading :

• A monstrously long survey paper with links to hundreds of articles on the topic

• Nature paper : Rate of de novo mutations and the importance of father's age to disease risk

• Lightweight summary of the Nature paper

• Another summary of the Nature paper

• Critical Analysis by FiveThirtyEight