Most Adults Carry High Genetic Risk for Three Common Diseases, Study of 1 Million Genomes Finds

A comprehensive new analysis of nearly one million human genomes has established the first quantitative baseline for normal genetic variation. Published on October 22, 2026, in the journal Genome Medicine, the research reveals that carrying a high genetic predisposition for multiple chronic illnesses is a standard feature of human biology rather than an anomaly.[4][5]

The study, led by researchers at the University of Exeter, utilized whole-genome sequencing data from two massive population repositories: the UK Biobank and the United States-based All of Us research program. By examining this vast dataset, scientists aimed to define what an average genome actually looks like before it is used to predict a patient's medical future.[4][6]

The research team evaluated polygenic risk scores across 28 common conditions, including type 2 diabetes, cardiovascular disease, and schizophrenia. These scores calculate an individual's cumulative susceptibility by aggregating thousands of tiny genetic variations, each of which contributes a fractional amount to the overall risk profile.[1][6]

The results demonstrated that elevated risk is ubiquitous across the population. According to the data, the average person ranks in the top 10 percent for genetic risk for nearly three of the 28 evaluated conditions, meaning almost everyone carries a pronounced vulnerability to something.[1][6]

At the extreme end of the spectrum, the prevalence remains surprisingly high. The researchers found that approximately one in five individuals—20 percent of the population—ranks in the top one percent of genetic risk for at least one of the polygenic scores assessed.[1][6]

"Whole genome sequencing has become such an important tool in diagnosing genetic disease, and we're increasingly moving towards genetic screening for predicting disease," said senior author Professor Caroline Wright of the University of Exeter. "Yet most people are unaware of just how much genetic variation is present in every genome."[1][4]

Inside the Average Genome

To contextualize these risk scores, the study quantified the sheer volume of differences that define a standard human blueprint. The researchers determined that the average human genome contains between 4.3 million and 5.3 million genetic variants, or specific locations where the DNA sequence diverges from the reference standard.[1][4]

The vast majority of these millions of variants are biologically neutral, exerting no measurable impact on a person's health. However, approximately 10,000 of these variants actively alter gene sequences, influencing everyday physical traits and biological processes ranging from lactose intolerance to how the body metabolizes specific medications.[1][4][6]

The study also shed light on the prevalence of potentially dangerous mutations hiding in healthy individuals. The data indicates that every person carries between one and three rare genetic variants that have been previously classified as pathogenic, meaning they are known to cause serious single-gene disorders.[1][4][6]

Because many of these severe conditions are recessive, requiring two copies of the mutated gene to manifest, individuals carrying a single disease-causing variant typically remain healthy carriers. Furthermore, the average person harbors about 50 rare variants of uncertain clinical significance, whose actual effects on human health remain entirely unknown.[1][4][6]

The researchers also tracked how new genetic material enters the population by examining participants who were sequenced alongside their parents. They discovered that the average individual possesses around 63 de novo variants—entirely new mutations that were not present in either the mother's or the father's genome.[4]

These novel mutations originate primarily during the formation of reproductive cells, with a distinct skew toward paternal inheritance. The study quantified this effect, finding that the number of de novo mutations increases by approximately 1.2 additional variants for every year of the father's age at conception.[4]

The Danger of Overdiagnosis

While the sheer volume of genetic risk factors might sound alarming, the researchers emphasized a critical distinction between genetic predisposition and clinical destiny. Ranking in the top 10 percent for cardiovascular disease risk does not equate to a 10 percent probability of actually suffering a heart attack, nor does it guarantee that the disease is inevitable.[6]

"Importantly, we found that everyone carries a small number of genetic variants linked to disease, although many of these will not actually cause disease in that individual," Wright explained. The presence of risk-associated DNA is merely one variable in a complex biological equation.[1]

For complex chronic conditions like diabetes or schizophrenia, genetic architecture only sets the baseline susceptibility. Whether that risk translates into actual illness depends heavily on environmental exposures, lifestyle choices, family history, and other clinical factors that DNA sequencing cannot capture.[6]

As direct-to-consumer genetic testing becomes increasingly popular, public health experts warn that delivering raw polygenic risk scores without clinical context could trigger widespread harm. Informing healthy individuals that they harbor high genetic risk for multiple diseases risks generating unnecessary anxiety, driving unwarranted follow-up testing, and fueling overdiagnosis.[4]

The Diversity Gap

Despite the massive scale of the analysis, the researchers acknowledged a significant structural limitation in their foundational data. The participants drawn from the UK Biobank and the All of Us program are disproportionately of Western European ancestry, reflecting a longstanding bias in global genomic research.[6]

This lack of diversity severely restricts the universal applicability of the study's specific polygenic risk scores. Because genetic architecture varies across different populations, a risk score calibrated on European genomes may miscalculate the actual disease risk for individuals of African, Asian, or Indigenous descent.[6]

Expanding these baseline measurements to encompass a truly global population remains a critical hurdle for the field. Until biobanks incorporate more genetically diverse cohorts, clinicians in regions like India and sub-Saharan Africa will struggle to apply these predictive tools accurately to their own patients.[6]

The Exeter study provides a vital reality check for the era of personalized medicine. By defining the immense variation inherent in a normal genome, the research establishes a necessary reference point for clinicians attempting to separate meaningful genetic warnings from background biological noise.[4][6]

Genetic testing remains a powerful diagnostic tool, but it is not a definitive crystal ball. As genomic screening transitions from specialized clinics to routine healthcare, understanding that high genetic risk is an ordinary human trait will be essential for both doctors and patients.[6]