Most people have high genetic risk for three common diseases, study finds

Most people have a high genetic risk score for around three common diseases, including diabetes, cardiovascular disease and schizophrenia, but this does not mean they are destined to develop them, according to a new study published in Genome Medicine.

Researchers led by the University of Exeter analysed genetic data from nearly one million people in the UK Biobank and the US All of Us research programme. The study examined genetic risk scores for 28 diseases.

On average, participants ranked in the top 10% of genetic risk scores for around three conditions. However, a high score indicates a greater predisposition to a disease, not a 10% chance of developing it or a certainty of falling ill.

The researchers also found that the average human genome contains around 4.3 million to 5.3 million genetic variants. Most are harmless or have no clearly measurable effect on health.

An average person also carries around one to three rare variants classified as pathogenic or likely pathogenic in certain genes associated with single-gene disorders. However, people carrying a single disease-causing variant may be healthy carriers, particularly for recessive conditions.

The study further found that people carry around 50 rare genetic variants of uncertain significance on average. These are variants whose effects on health remain unclear due to insufficient evidence.

The findings highlight the limitations of interpreting genetic test results as predictions of future illness. Researchers cautioned that reporting multiple genetic risk scores could cause unnecessary anxiety, follow-up testing and overdiagnosis.

Genetic testing can help diagnose inherited disorders, guide treatment decisions and identify people who may benefit from preventive measures. However, the usefulness of a test depends on what it measures and how reliably its findings predict health outcomes.

The study also noted that people of Western European ancestry were over-represented in the datasets. More diverse genetic research is needed to establish how reliably these risk scores apply to populations such as those in India.