Potentially harmful DNA mutations can amass in men's sperm as they age, new research has found, which may in turn impact the number of mutations passed on to children – and the risks of disease in the next generation.

Mutations occur in DNA when cells replicate, and arise either by random chance or because of environmental stresses. They can impact how well the body works, or have no observable effect at all. Mutations accumulate as time goes by, just like wear and tear on a car – but it hasn't been clear how much these genetic mishaps affect sperm in older men.

Researchers from the Wellcome Sanger Institute and King's College London in the UK used a new high-resolution analysis technique called NanoSeq to look in detail at mutations in the sperm of men aged 24-75 years, and the genes those mutations affected.

Not only do mutations occur at higher rates in older men, the data showed, but some are 'selfish' – giving the cells that carry them a growth advantage, so they replicate faster than or outlast other cells in the testes and gradually take over. Many of these mutations have previously been linked to developmental disorders and cancers.

"We expected to find some evidence of selection shaping mutations in sperm," says geneticist Matthew Neville, from the Wellcome Sanger Institute.

"What surprised us was just how much it drives up the number of sperm carrying mutations linked to serious diseases."