Genome damage makes people slightly less likely to have children

A damaged genome may contribute to reduced reproduction in some people, recent evidence suggests.

Professor Matthew Hurles, head of human genetics at the Wellcome Sanger Institute, and colleagues, suggested that increased childlessness is an evolutionary process that removes genome damaging genetic variants from the population. Men and women with these genetic variants may be less likely to form reproductive partnerships due to genetic influences on their cognition and behaviour.

'We have shown that people with damaged genomes, particularly men, are slightly more likely to be childless.' explained first author Dr Eugene Gardner. 'This is probably due to the effect of damaging genetic variants on cognitive and behavioural traits, which make these men less likely to find a partner to have children with.'

Published in the journal Nature, the researchers firstly investigated the association between damaging genetic variants and decreased reproductive success. Data from 340,925 UK Biobank participants aged between 39 and 73 years were analysed. Each individual's genetic burden – how much damaging genetic variation someone carries across their genome, was calculated. Men with the highest genetic burden were found to have 0.26 fewer children – an association not seen in females.

The team then considered whether genetic burden was associated with increased risk of childlessness due to; reduced fertility, adverse health conditions, or cognitive and behavioural factors.

The authors showed that genetic burden was not associated with higher risk of female or male infertility.

Physical defects have been previously associated with reduced reproduction, hence, the team investigated the contribution of adverse health conditions on genetic burden and increased childlessness. The team found it was unlikely that a damaged genome increased the risk of health conditions that could fully account for the reduced reproductive success seen in men in this study.

This study also considered whether; living with a partner, having had sex, having a mental health disorder associated with reduced reproductive success, having a university degree and having an infertility code in health records, were factors associated with increased childlessness. These factors accounted for 68 percent of the association between genetic burden and childlessness in males but only 16 percent in females. The largest contribution came from living with a partner and having had sex. However, despite the significant association between genetic burden and childlessness, it explained less than one percent of the likelihood of childlessness in both sexes.

'It's important to emphasise that we have not found a "gene for childlessness", as that implies a strong, causal effect of genetic variation on whether or not someone will have children.' reminded Dr Gardner. 'Similarly, we cannot use these results to "predict" whether or not these damaging genetic variants will be linked with childlessness, as both genetics and the environment influence our behaviour, cognitive abilities and personalities.'

The findings of this study are based on individuals from a single study, all of European ancestry, and the authors suggest a need for similar studies across different populations and cultures.