It’s a common belief that chronic diseases like heart disease or diabetes are purely a result of lifestyle choices. While diet and exercise are critical, new research reveals a far more complex truth: our genes and our environment don’t act alone, they interact in intricate ways that significantly change our disease risk. Understanding these gene-environment interactions is key to unlocking the future of personalized medicine.
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Beyond “Good” Genes and “Bad” Habits
For decades, scientists have known that both our genetic blueprint and external factors influence our health. We inherit predispositions, but our surroundings and choices—like the air we breathe, the food we eat, and the medications we take—also play huge roles.
For diseases caused by a single gene mutation, like cystic fibrosis, the link is relatively clear. But most chronic diseases, like type 2 diabetes or schizophrenia, are polygenic, meaning they are influenced by hundreds or even thousands of small genetic variations scattered across our DNA. Just like assembling a complex puzzle, many pieces need to come together to increase risk.
Historically, studying how these myriad genetic pieces interact with countless environmental factors has been incredibly difficult due to technical challenges and a lack of comprehensive data. Researchers often had to study them in isolation.
Mapping the Interactions Across the Genome
Our recently published research aimed to bridge this gap. We developed new computational tools to analyze large datasets that combine genetic information with detailed health and environmental data. Using the UK Biobank, a resource containing data from half a million individuals, we investigated how millions of genetic variations jointly influence 33 complex traits and diseases under different environmental conditions, including smoking, diet, and air pollution.
Instead of looking for rare, large effects from a single gene (like the aspirin example below), we focused on how the combined effect of many genes changes depending on the environment.
The Surprising Case of Aspirin and Cancer
Consider the relationship between taking aspirin regularly and colon cancer risk. Early research found that aspirin’s protective effect wasn’t the same for everyone. It was stronger in people with a specific genetic variation that caused their bodies to break down aspirin more slowly, keeping drug levels higher for longer. This was a clear example of a gene-environment interaction where a single gene influenced how well an environmental factor (a medication) worked.
However, such clear-cut, single-gene interactions are uncommon for most complex diseases. The effects of individual genetic variants are usually tiny. So, how do you find the subtle ways hundreds of genes might interact with environmental exposures?
Visual representation of how genetic and environmental factors interact to influence biological outcomes.
Three Ways Genes and Environment Interact
By looking at the collective impact of genes across the entire genome, we identified three distinct ways they interact with environmental exposures:
- Different Effects: Sometimes, the same set of genes has a different strength of effect on a trait depending on the environment. For instance, the way genetics influences white blood cell counts in the body differed significantly between smokers and non-smokers, suggesting smoking fundamentally alters the genetic influence on these cells.
- Changing Heritability: In some cases, the overall influence of genetics on a trait changes depending on the environment. We found that the heritability of body mass index (BMI) was higher in people who were more physically active. This means that if you are active, your genes play a proportionally larger role in determining your BMI than if you are inactive. We saw similar patterns for other traits like cholesterol levels and alcohol consumption.
- Joint Amplification: For certain traits, both genetic and environmental influences seem to grow together. As people reported spending more time watching television, both the genetic and environmental factors influencing their waist-to-hip ratio increased. This likely captures the interplay with related behaviors like reduced physical activity that often accompany more TV time.
We also found that biological sex can act as a factor in these interactions, influencing how genes affect traits like neuroticism.
Towards Personalized Health Strategies
These findings offer a new framework for understanding how our genes and environment work together. Different types of interactions might point to environmental factors altering different steps in biological pathways—the complex networks of genes and molecules that work together in our cells.
Ultimately, a deeper understanding of these polygenic gene-environment interactions could revolutionize healthcare. Instead of one-size-fits-all advice or treatments, doctors might one day use your unique genetic profile combined with information about your lifestyle and environment to predict disease risk more accurately and recommend the most effective personalized prevention or treatment strategies. Imagine knowing whether diet changes, a specific exercise plan, or a particular medication is most likely to benefit you based on how your genes interact with those factors.
This research highlights that disease risk isn’t just about the hand of genes you’re dealt or the environment you live in—it’s about the dynamic interplay between the two, a dance that scientists are only just beginning to fully understand.
