One of the most enduring questions humans have is how long we’re going to live. With this comes the question of how much of our lifespan is shaped by our environment and choices, and how much is predetermined by our genes.

A study recently published in the prestigious journal Nature Medicine has attempted for the first time to quantify the relative contributions of our environment and lifestyle versus our genetics in how we age and how long we live.

The findings were striking, suggesting our environment and lifestyle play a much greater role than our genes in determining our longevity.

What the researchers did

This study used data from the UK Biobank, a large database in the United Kingdom that contains in-depth health and lifestyle data from roughly 500,000 people. The data available include genetic information, medical records, imaging and information about lifestyle.

A separate part of the study used data from a subset of more than 45,000 participants whose blood samples underwent something called “proteomic profiling”.

Proteomic profiling is a relatively new technique that looks at how proteins in the body change over time to identify a person’s age at a molecular level. By using this method researchers were able to estimate how quickly an individual’s body was actually ageing. This is called their biological age, as opposed to their chronological age (or years lived).

The researchers assessed 164 environmental exposures as well as participants’ genetic markers for disease. Environmental exposures included lifestyle choices (for example, smoking, physical activity), social factors (for example, living conditions, household income, employment status) and early life factors, such as body weight in childhood.

They then looked for associations between genetics and environment and 22 major age-related diseases (such as coronary artery disease and type 2 diabetes), mortality and biological ageing (as determined by the proteomic profiling).

These analyses allowed the researchers to estimate the relative contributions of environmental factors and genetics to ageing and dying prematurely.

What did they find?

When it came to disease-related mortality, as we would expect, age and sex explained a significant amount (about half) of the variation in how long people lived. The key finding, however, was environmental factors collectively accounted for around 17% of the variation in lifespan, while genetic factors contributed less than 2%.

This finding comes down very clearly on the nurture side in the “nature versus nurture” debate. It suggests environmental factors influence health and longevity to a far greater extent than genetics.

Not unexpectedly, the study showed a different mix of environmental and genetic influences for different diseases. Environmental factors had the greatest impact on lung, heart and liver disease, while genetics played the biggest role in determining a person’s risk of breast, ovarian and prostate cancers, and dementia.

The environmental factors that had the most influence on earlier death and biological ageing included smoking, socioeconomic status, physical activity levels and living conditions.

Interestingly, being taller at age ten was found to be associated with a shorter lifespan. Although this may seem surprising, and the reasons are not entirely clear, this aligns with previous research finding taller people are more likely to die earlier.

Carrying more weight at age ten and maternal smoking (if your mother smoked in late pregnancy or when you were a newborn) were also found to shorten lifespan.

Probably the most surprising finding in this study was a lack of association between diet and markers of biological ageing, as determined by the proteomic profiling. This flies in the face of the extensive body of evidence showing the crucial role of dietary patterns in chronic disease risk and longevity.

But there are a number of plausible explanations for this. The first could be a lack of statistical power in the part of the study looking at biological ageing. That is, the number of people studied may have been too small to allow the researchers to see the true impact of diet on ageing.

Second, the dietary data in this study, which was self-reported and only measured at one time point, is likely to have been of relatively poor quality, limiting the researchers’ ability to see associations. And third, as the relationship between diet and longevity is likely to be complex, disentangling dietary effects from other lifestyle factors may be difficult.

So despite this finding, it’s still safe to say the food we eat is one of the most important pillars of health and longevity.

What other limitations do we need to consider?

Key exposures (such as diet) in this study were only measured at a single point in time, and not tracked over time, introducing potential errors into the results.

Also, as this was an observational study, we can’t assume associations found represent causal relationships. For example, just because living with a partner correlated with a longer lifespan, it doesn’t mean this caused a person to live longer. There may be other factors which explain this association.

Finally, it’s possible this study may have underestimated the role of genetics in longevity. It’s important to recognise genetics and environment don’t operate in isolation. Rather, health outcomes are shaped by their interplay, and this study may not have fully captured the complexity of these interactions.

The future is (largely) in your hands

It’s worth noting there were a number of factors such as household income, home ownership and employment status associated with diseases of ageing in this study that are not necessarily within a person’s control. This highlights the crucial role of addressing the social determinants of health to ensure everyone has the best possible chance of living a long and healthy life.

At the same time, the results offer an empowering message that longevity is largely shaped by the choices we make. This is great news, unless you have good genes and were hoping they would do the heavy lifting.

Ultimately, the results of this study reinforce the notion that while we may inherit certain genetic risks, how we eat, move and engage with the world seems to be more important in determining how healthy we are and how long we live.

Hassan Vally, Associate Professor, Epidemiology, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.