PEOPLE unwittingly tend to choose a partner who is likely to have a similar life expectancy, according to new research.

A genetic study found humans also unconsciously select mates who share similar risks of illnesses, such as high blood pressure.

Experts say the findings help explain why long-term couples often suffer from the same ailments in later years.

Researchers at the University of Edinburgh examined data from the UK Biobank - a major study of genes and lifestyle factors linked to health.

The team looked at information from the parents of couples and found even in-laws shared genetic risk factors for diseases.

The similarities are greater than would be expected by chance, experts said.

Given that many ailments are not visible when people choose their partners, experts say the surprising finding is most likely a result of choosing a mate with shared lifestyle factors that are genetically linked to disease.