PRS: The Science of Predicting Future Predispositions with Genetics
Could your genes reveal something about your future health? Discover how polygenic risk scores (PRS) combine information from many genetic variants to estimate disease predisposition, why ancestry matters, and how genetic risk insights may support informed health decisions. Copy excerpt
What If Your Family’s Health History Could Tell You Something About Your Future?
Think about your family for a moment.
Perhaps your grandfather lived with diabetes for years. Maybe your mother has high blood pressure, or your father has been taking medication for a heart condition. You might even remember a relative who developed a serious illness at a surprisingly young age. In many families, these stories become familiar. Someone might say, “Diabetes runs in our family,” or “Heart problems are common on our side.”
But have you ever wondered what that actually means for you?
Does having a parent with diabetes mean you will develop it too? If your grandparents experienced heart disease, could you have a higher chance of developing the same condition? And is there anything you can learn about your health before symptoms appear?
Family history can provide valuable clues. It may reflect shared genes, similar lifestyles, common environmental exposures, or a combination of these factors. However, family history alone cannot tell the whole story.
This is where modern genetic science offers another perspective.
Scientists can now study thousands of small differences in a person’s DNA to understand how they may contribute to the likelihood of developing certain diseases. By combining information from many genetic variants, they can calculate something called a Polygenic Risk Score (PRS). PRS does not predict your future with certainty. Instead, it provides information about one part of your health risk: the contribution of many inherited genetic differences.
Understanding this information may help you have more informed conversations about your health, screening options, and preventive care.
Let’s explore how it works, what it can tell you, and where its limitations lie.
1. What Is a Polygenic Risk Score (PRS)?
A Polygenic Risk Score, commonly called PRS, is a numerical score that combines the effects of many genetic variants associated with a particular trait or disease.
To understand the idea, think about the factors that influence your health.
Your risk of developing type 2 diabetes, for example, may be influenced by your genetic background, age, body weight, physical activity, diet, sleep, and other health-related factors.
Some genetic differences may contribute a small amount to your predisposition. Others may have a different effect. A PRS combines the estimated contributions of selected variants into a single score.
The word polygenic means that many genes or genetic variants contribute to a characteristic. The word risk refers to the likelihood of an outcome, while score represents the numerical summary of the genetic information.
In simple terms, a PRS helps answer this question:
Compared with an appropriate reference population, do your genetic variants suggest a relatively higher or lower predisposition to a particular disease?
For example, two people may have similar diets and levels of physical activity but different genetic risk profiles for coronary artery disease. A validated PRS may help identify some of that difference.
However, their overall health risks could still differ because of blood pressure, cholesterol, smoking, medical history, and many other factors.
A PRS is therefore one piece of the health puzzle, not a complete picture.
2. How Is a Polygenic Risk Score Calculated?
The calculation may sound complicated, but the underlying idea is relatively straightforward: identify relevant genetic variants, estimate their contributions to a disease, and combine those contributions into a score.
Here is how scientists generally develop a PRS.
Step 1: Study genetic data from large groups of people
Researchers examine DNA data from large populations, comparing people with a particular condition against those without it. These studies are often called Genome-Wide Association Studies (GWAS). They help researchers identify genetic variants statistically associated with a disease or trait.
For example, a large study may identify thousands of variants associated with coronary artery disease. Each variant may have a relatively small effect, but their combined contribution can be meaningful.
An association does not automatically mean that a variant directly causes a disease.
Step 2: Identify relevant genetic variants
Scientists select variants that are informative for the disease being studied. A genetic variant is a difference in DNA sequence between individuals. Many common variants involve a change in a single DNA letter, such as A, C, G, or T. The selected variants depend on the disease, the available research, and the method used to develop the score.
Step 3: Assign weights to the variants
Not every genetic variant contributes equally to the calculated score.
Researchers estimate the strength and direction of each variant’s association with the disease. These estimates are used as weights in the calculation. A variant associated with increased risk may contribute positively to the score, while another associated with lower risk may contribute in the opposite direction, depending on the scoring method.
Step 4: Combine the genetic information
A simplified PRS calculation can be represented as:
PRS = Sum of (number of effect alleles × weight for each variant)
An allele is one version of a genetic variant. At a typical two-copy autosomal position, a person may carry zero, one, or two copies of a selected effect allele. The score combines the relevant allele counts with their corresponding weights across the selected variants. Imagine a simplified example in which three variants have weights of 0.2, 0.4, and 0.1. If a person carries one, two, and one copies of the respective effect alleles, the illustrative score would be:
(1 × 0.2) + (2 × 0.4) + (1 × 0.1) = 1.1
This is only a teaching example, not a real disease score. Actual PRS calculations may involve thousands or millions of variants and require carefully developed statistical methods.
Step 5: Compare the score with an appropriate reference
A raw PRS is not automatically a percentage chance of developing a disease. To interpret it, researchers may compare the score with a reference population, calculate a percentile, or use a validated model to estimate relative risk. Estimating absolute risk requires additional information and appropriate clinical or population data. The quality of the result depends on the data used, the scoring method, the reference population, and how well the model has been validated.
3. Why Is PRS Important?
For many common diseases, there is no single genetic variant that explains everyone’s risk. Instead, numerous genetic variants may contribute alongside lifestyle, environmental, and other factors. PRS offers a way to summarize some of this inherited genetic contribution.
It may be useful in several ways.
Understanding inherited predisposition: A PRS can provide information about genetic risk that may not be obvious from family history alone.
Identifying people who may benefit from closer assessment: In certain settings, a validated score may help identify people whose genetic risk is higher than average, even if they do not have obvious symptoms.
Supporting personalized prevention: When combined with established health information, a PRS may help inform discussions about screening, risk-factor management, and preventive care.
Adding another perspective to family history: Family history tells us what has happened among relatives. Genetic analysis can provide additional information about inherited variants associated with disease.
However, a PRS does not replace family history, routine health checks, or a healthcare professional’s assessment. Its value depends on whether the score has been shown to improve decisions for the particular disease and population.
4. Which Diseases Can a PRS Assess?
There is no single fixed number of diseases that can be assessed using PRS.
Researchers have developed polygenic scores for many complex diseases and traits. However, the availability of a score does not mean it is equally accurate, clinically useful, or suitable for every person.
Here are some important examples.
Coronary artery disease
Coronary artery disease occurs when the blood vessels supplying the heart become narrowed or blocked, often because of plaque buildup.
Many genetic variants are associated with this condition. A validated PRS may help identify people with a higher inherited predisposition, potentially adding information to conventional risk assessment.
However, blood pressure, cholesterol, smoking, diabetes, age, and other factors remain important.
Type 2 diabetes
Type 2 diabetes develops through a combination of genetic susceptibility, biological factors, and environmental influences. A PRS may summarize part of the genetic contribution. It cannot determine with certainty whether someone will develop diabetes. Weight management, physical activity, appropriate nutrition, and recommended blood glucose testing remain important regardless of the score.
Certain cancers
Polygenic scores have been studied for several cancers, including breast and prostate cancer. They estimate the combined contribution of selected common genetic variants. They are different from tests that identify certain rare, high-impact variants, such as disease-associated variants in BRCA1 or BRCA2. A PRS should not be used to rule out cancer or replace recommended screening. Personal and family history may indicate the need for additional assessment even when a polygenic score is not high.
Other conditions
Research has also explored polygenic scores for conditions and traits involving:
- Atrial fibrillation, a type of irregular heart rhythm.
- High cholesterol and other cardiometabolic traits.
- Some autoimmune and inflammatory conditions.
- Certain neurological and psychiatric conditions.
- Other complex diseases and biological characteristics.
The strength of evidence varies considerably across these applications.
An important distinction: Scientists may be able to calculate a score for a disease without having enough evidence to use it for routine clinical decisions. A meaningful health report should distinguish research findings from validated, clinically useful applications.
5. Can PRS Tell You Whether You Will Develop a Disease?
This is one of the most important questions to understand.
No. A PRS cannot tell you with certainty whether you will develop a disease.
It estimates genetic predisposition, not a guaranteed future outcome. Imagine two people with a relatively high PRS for type 2 diabetes. One person may develop the condition, while the other may not. Their age, lifestyle, other medical conditions, environmental exposures, and many additional factors can influence their outcomes. Likewise, someone with a low PRS can still develop the disease.
It is helpful to distinguish three ideas:
- Genetic predisposition: How inherited genetic differences may influence susceptibility.
- Relative risk: How risk compares with that of a defined reference group.
- Absolute risk: The estimated chance of developing a condition over a specified period.
These measures answer different questions. A high genetic score does not automatically mean a high absolute probability of disease, and a low score does not guarantee protection. PRS is best understood as a tool for improving risk awareness, not as a crystal ball.
6. Percentage vs. Percentile: What Is the Difference?
When reading a genetic report, percentage and percentile can sound similar, but they mean different things. Understanding the difference is essential for interpreting PRS results correctly.
What does percentage mean?
A percentage describes a proportion out of 100.
For example, if 20 out of 100 people in a hypothetical group develop a condition over a specified period, the proportion is 20%. That does not mean every individual in the group has exactly a 20% chance of developing the condition. The figure describes the group, and an individual’s risk may differ. In health reporting, a percentage may represent an absolute risk estimate, but only when the report explicitly defines it that way.
What does percentile mean?
A percentile describes a person’s position relative to a reference group.
Suppose your PRS for a particular condition is at the 90th percentile of an appropriate reference population.
This means your score is higher than, or approximately as high as, the scores of 90% of people in that reference distribution, subject to the method used.
It does not mean that you have a 90% chance of developing the disease.
A percentile describes the ranking of a score, not the probability of a future health outcome.
A simple comparison
| Term | What it tells you | Example |
|---|---|---|
| Percentage | A proportion or probability, depending on context | An estimated 10% chance of an outcome over a defined period |
| Percentile | Position relative to a reference distribution | A PRS at the 90th percentile |
| Relative risk | Risk compared with a specified group | Twice the risk of a reference group |
| Absolute risk | The estimated probability of an outcome over a defined period | A 4% chance over 10 years |
The examples are illustrative and are not medical predictions.
Why does this distinction matter?
A report showing a PRS at the 95th percentile may initially sound alarming. However, the percentile alone does not tell you how likely you are to develop the disease.
The score’s relationship to actual disease risk must be established using appropriate research and validation. A healthcare professional can help interpret it alongside age, medical history, family history, and conventional risk factors.
7. Why Do Population Differences Matter in PRS?
Genetic research has made significant progress, but one important challenge remains: a score developed in one population may not perform equally well in another.
This matters because people around the world have different patterns of genetic variation. The frequency of particular variants and the relationships between nearby variants can differ among populations.
Many early large-scale genetic studies included disproportionately high numbers of participants with European ancestry. Consequently, some scores developed from these studies may be less accurate when applied to people from other ancestral backgrounds.
What does this mean for Indian and South Asian populations?
India has a highly diverse population, with substantial genetic diversity among and within different communities.
A PRS developed primarily using European-ancestry data should not automatically be assumed to have the same predictive performance for an Indian or South Asian individual.
Researchers need to evaluate how well a score works in the intended population. This includes checking its accuracy, calibration, and usefulness for real health decisions.
A model may require additional research, recalibration, or further development before it can be used reliably in a different population.
This is not because one population has inherently better or worse genes. It reflects differences in the data used to build and validate the model.
For consumers, an important question is therefore not simply, “Can I get a PRS?” but also, “Has this score been validated for people with a genetic background similar to mine?”
Greater representation of diverse populations in genetic research can help make future risk assessment more equitable and reliable.
8. Is PRS Accepted by Medical Doctors?
Polygenic risk scores are a legitimate area of medical and genetic research, and some are beginning to enter clinical practice in selected settings.
For example, the American Heart Association published a scientific statement in 2022 discussing the potential clinical applications and limitations of PRS for cardiovascular disease.
Research suggests that some scores may improve risk assessment when combined with established clinical information. However, the usefulness of PRS depends on the disease, the quality of the evidence, the population being assessed, and whether the result changes a clinical decision.
This means there is no single answer that applies to every doctor, hospital, or disease.
In practice, healthcare professionals may consider PRS alongside other evidence in appropriate circumstances. Its use is not yet routine for every condition, and availability varies across healthcare systems.
A PRS should not independently determine whether someone starts medication, stops treatment, or skips a screening test.
Before relying on a score for medical decisions, it is important to ask:
- Has the score been independently validated?
- Is it suitable for my ancestry and population?
- Does it provide useful information beyond conventional risk factors?
- Can the result guide an established preventive or clinical decision?
- Should a genetic counsellor or other qualified healthcare professional help interpret it?
The goal is not simply to obtain a genetic number. It is to understand whether the information can support a better-informed decision.
9. Can PRS Help With Early Detection and Prevention?
One of the most promising aspects of PRS is its potential to support earlier awareness of inherited risk.
Many common diseases develop gradually. Risk factors may be present for years before a person notices symptoms.
If a validated PRS identifies a higher genetic predisposition, it may encourage a person to discuss appropriate screening or risk assessment with a healthcare professional.
For example, a clinician may consider a person’s genetic information alongside cholesterol levels, blood pressure, family history, and other established indicators when assessing cardiovascular risk.
For someone concerned about type 2 diabetes, genetic information may contribute to a broader conversation about conventional risk factors and appropriate blood glucose testing.
However, a PRS does not detect a disease that is already present. It estimates predisposition. Early detection usually requires suitable screening, clinical assessment, or diagnostic testing.
What can you do with the information?
Understand your family history. Record which relatives experienced a condition, the type of condition, and, where known, the age at diagnosis. This information can help a healthcare professional assess inherited and shared risk factors.
Follow appropriate screening recommendations. Do not wait for a genetic report before attending recommended health checks. Your age, symptoms, medical history, and family history may already indicate the need for screening.
Discuss your risk factors with a healthcare professional. If a validated score suggests higher risk, ask whether additional assessment or a different screening approach is appropriate.
Maintain healthy habits. Regular physical activity, balanced nutrition, avoiding tobacco, adequate sleep, and maintaining a healthy weight can support long-term health. The appropriate approach depends on your individual circumstances.
Use the information thoughtfully. A high score should not create unnecessary fear, and a low score should not create false reassurance.
Genetic information is most useful when it supports informed action rather than anxiety.
10. Does Family History Still Matter if You Have a PRS?
Absolutely.
A PRS and a family health history provide different kinds of information, and one does not replace the other.
Family history can reflect shared genes, environmental exposures, lifestyle habits, and combinations of these influences. It may also reveal patterns that deserve further investigation.
For example, if several close relatives developed a particular disease at unusually young ages, a healthcare professional may recommend a more detailed assessment. In some circumstances, this could include testing for a specific inherited genetic condition rather than relying only on a PRS.
This distinction is important because certain rare genetic variants can have a substantial effect on disease risk, while a PRS generally summarizes the combined effects of many variants, often common ones.
A person can have a high polygenic score without a strong family history. Equally, a strong family history can warrant medical attention even if a polygenic score appears low.
The most informative approach may combine family history, genetic information where appropriate, medical history, and conventional clinical risk factors.
Your family’s story is an important starting point, but it is not the whole prediction.
11. Can Raw DNA Data Be Used to Calculate a PRS?
DNA testing can provide genetic information that may be useful for different forms of analysis, depending on the type of test and the data available.
Some testing services provide customers with access to their raw genetic data. This is data containing information about the genetic variants measured or analysed by the testing platform.
However, having a raw DNA file does not automatically mean you have a validated Polygenic Risk Score.
A suitable PRS analysis generally requires several components:
- Genetic data that adequately captures the variants needed for the selected score.
- A clearly defined PRS model with the relevant genetic variants and their weights.
- Appropriate quality control and data-processing methods.
- A suitable reference population and validated interpretation method.
- Additional clinical or population information if an absolute risk estimate is intended.
A raw file may not contain every variant required by a particular PRS. Some analyses may require imputation or other processing, and these steps introduce additional assumptions and potential uncertainty.
The suitability of the data also depends on whether the score has been validated for the person’s population and intended use.
Explore your genetic data with GenoConnect
If you are interested in learning more about your genetic information, GenoConnect provides a starting point for exploring its DNA testing options and related resources.
Visit GenoConnect to explore the available testing options. You can also visit the DNA Reports section to learn more about the available DNA-related information.
Before choosing a test, check what type of genetic data it provides, which variants are covered, and whether the resulting data is suitable for your intended analysis.
Access to raw data can be useful for further exploration, but the availability of a clinically validated PRS or disease-specific report should be confirmed separately.
12. What Are the Limitations of PRS?
PRS has considerable potential, but it is important to understand what it cannot do.
It cannot guarantee a future outcome. A high score does not mean you will definitely develop a disease, and a low score does not mean you are protected.
It does not explain every cause of disease. Most PRS models capture only part of the genetic contribution. Environmental, lifestyle, biological, and other factors also matter.
Its accuracy varies by condition and population. A score that performs well in one group may be less reliable in another.
It is not the same as a diagnostic test. PRS estimates predisposition. It does not establish whether a disease is currently present.
Not every available score is clinically useful. A score may be scientifically interesting without being sufficiently validated to guide individual healthcare decisions.
Results need careful interpretation. Percentiles, relative risk, and absolute risk describe different things. Confusing them can lead to unnecessary worry or false reassurance.
Genetic information deserves privacy. DNA data is personal and potentially informative about biological relatives as well. Before sharing it with a third-party analysis service, review how the data will be stored, used, and protected.
These limitations do not make PRS useless. They explain why its results should be interpreted in context and used responsibly.
13. The Future of PRS: Moving Towards More Personalized Health
Genetic science is continually improving our understanding of why people with similar lifestyles can experience different health outcomes.
As larger and more diverse genetic datasets become available, researchers can develop and evaluate better polygenic scores. They are also studying how genetic information can be combined with clinical measurements, family history, and other health data.
In the future, carefully validated PRS models may help refine risk assessment for selected conditions and support more personalized preventive strategies.
For this progress to benefit more people, researchers must address important challenges, including population representation, model accuracy, clinical usefulness, affordability, privacy, and responsible communication of results.
The aim is not to predict every illness or reduce a person’s health to a genetic number. It is to identify useful information that can support better decisions.
For consumers, the most important question will remain whether a genetic result is reliable, relevant to their population, and useful for a real health decision.
Conclusion: Your Genes Are Part of Your Story, Not Your Destiny
When a disease affects someone we love, it is natural to wonder whether the same thing could happen to us.
Family history gives us a starting point. Modern genetic science adds another perspective by helping researchers understand how many inherited genetic differences contribute to common diseases.
A Polygenic Risk Score combines the effects of selected genetic variants to estimate genetic predisposition. Depending on the condition and the strength of the evidence, it may contribute to a broader assessment of health risk and help inform conversations about prevention.
But a score is not a promise about the future. It cannot replace medical advice, appropriate screening, or the many everyday factors that influence health.
Your family history matters. Your genetic information may offer additional clues. And your health decisions should be based on the best available evidence, interpreted in the context of your individual circumstances.
Your DNA can offer insights into your health, but it does not write your entire future.
Explore Your DNA with GenoConnect
Curious about your genetic information? Explore GenoConnect to learn about available DNA testing options and discover what your genetic data may help you understand.
Whether you are exploring your ancestry, learning about your DNA, or considering further genetic analysis, start by understanding what your test includes and what its results can reliably tell you.
Learn about your DNA. Understand the possibilities. Make informed choices.
Health disclaimer: This article is intended for general educational purposes only and is not medical advice, a diagnosis, or a substitute for professional healthcare. Polygenic risk scores have different levels of validation and clinical usefulness across diseases and populations. Consult a qualified healthcare professional before making medical decisions based on genetic information.
References and further reading
- National Human Genome Research Institute (NHGRI). Polygenic Risk Scores.
- O’Sullivan JW, et al. Polygenic Risk Scores for Cardiovascular Disease: A Scientific Statement From the American Heart Association. Circulation. 2022;146:e93–e118. Read the scientific statement.
- Polygenic risk scores in the clinic: Translating risk into action. Read the review.