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1 In Every 3,600 British People Of European Descent Are Inbred: Study

A new study looking into the health effects of extreme inbreeding has found that 1 in every 3652 British people with European ancestry are inbred.

The study led by the University of Queensland, of around half a million people, found 125 participants whose genomes were consistent with what's been defined as "extreme inbreeding" -- that is, that they were offspring of first or second-degree relatives.

According to the American College of Medical Genetics, extreme inbreeding is prevalent in people who have 10 percent or more of the same DNA sequence inherited from both their biological mother and father.

It's the first time 10 percent or more homozygousity [stretches of DNA that are identical between the maternal and paternal copies] in the genome has been quantified in a sample of nearly half a million people, Dr. Loic Yengo, one of the study's authors, said.

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The study which used data from the UK Biobank found that people who were deemed as falling within that category were at 44 percent greater risk of being diagnosed with any kind of disease compared to the rest of the participants.

Previous research which has suggested inbreeding may lead to reduced stature, cognitive ability, lung function and fertility were also confirmed in the study published on Wednesday.

"Our study reinforced that inbreeding has negative consequences on health and implies that the overall burden of disease in populations can be reduced by policies that minimise it," the authors said.

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While "mating" between first or second-degree relatives is prohibited by British law, law enforcement records show that the UK is one of many countries where it continues to occur.

In their study, the authors stress it's difficult to put an exact figure of how prevalent extreme inbreeding is in the population but suggested their estimate could actually be too low.

They said that because of the stigma attached to incest and inbreeding, cases are often under-reported.

"Highly inbred individuals who suffer severe health consequences may be less likely to participate in a study," they added.

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Participants in the study were all older than 60 years of age, meaning the rate of extreme inbreeding was more indicative of a society in the 1960s or earlier.

Despite this, the authors said the rate of extreme inbreeding they detected was "in broad agreement" with the incidence of police-recorded incest offences in England and Wales between 2002 and 2017, which sits at 1 in every 5247 people.

Participants of non-European ancestry were also part of the study, but the authors found the numbers were too small to estimate the prevalence of extreme inbreeding in them.

The United Kingdom has a population of approximately 66 million. According to the office of national statistics, in 2017 around 1 in 7 of the population of the UK were born abroad.

Contact the author: vgerova@networkten.com.au