Most people may have a high genetic risk score for around three common diseases, including diabetes, cardiovascular disease and schizophrenia, according to a study published in the journal Genome Medicine.
Led by researchers at the University of Exeter in the United Kingdom, the study examined genetic variation across nearly one million individuals. The findings highlight how common genetic differences are and why a high genetic risk score does not necessarily mean someone will develop a disease.
Researchers analysed whole-genome sequencing data from two large population biobanks: the UK Biobank and the US-based All of Us research programme. Together, the datasets included more than 900,000 individuals.
The study found that the average human genome contains approximately 4.3 million to 5.3 million genetic variants. These are differences in DNA compared with a reference genome, and most do not have a measurable effect on health.
The team also examined polygenic risk scores for 28 common conditions using data from the UK Biobank. These scores combine information from multiple genetic variants to estimate a person's relative genetic susceptibility to a disease.
On average, participants ranked within the top 10% of genetic risk scores for approximately three conditions. However, the researchers did not assess participants' health status as part of this analysis, so a high score should not be interpreted as evidence that a person has a disease.
The findings underline the importance of interpreting genetic test results in context. Family history, symptoms, environmental exposures and other health factors can also influence disease development.
The researchers also highlighted a limitation of current genomic research: many populations remain underrepresented in genetic datasets. More diverse data will be important for improving the fairness and reliability of genetic risk assessment.

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