Have you ever wondered why some people live to 100, while others don’t make it past 70, even when they seem to live fairly similar lives?
For years, doctors and scientists have argued about how much of this comes down to the genes you’re born with versus the choices you make along the way. A new study has now put a number on it, and the answer might surprise you. It turns out one single thing plays a bigger role in how long you live than almost anything else, and it’s not what most people would guess.
Lifestyle habits make the biggest difference of all.
Before getting into the big discovery, it’s important to note that everyday choices still make a massive difference to how long someone lives. One study carried out in the UK found that swapping an unhealthy diet for one linked to a longer life could add up to 10 extra years onto someone’s lifespan. That’s a huge chunk of time, all from changing what ends up on your plate each day.
Smoking works in the opposite direction just as powerfully. Research has shown that smoking can shorten someone’s life by around 10 years overall, and one study even worked out that every single cigarette smoked costs a person about 20 minutes of their life. Other things known to affect how long people live include how active they are, how well they sleep, how connected they feel to friends and family, and how well they manage stress.
Scientists have found something that changes the whole picture.
Scientists in Israel have found that genetics might account for around 55% of how long a person lives, which is a lot more than most earlier studies suggested. That means more than half of your lifespan could come down to the genes passed on from your parents, rather than lifestyle choices alone.
What made this study different is that the scientists tried to remove other things from the equation that can cause someone to die early, like accidents or infections, before working out the number. Earlier studies hadn’t done this properly, which the researchers believe made genetics look far less important than it actually is.
Removing accidents and illness changed the numbers.
Think about it this way. If someone dies young because of a car accident, that has nothing to do with their genes at all, but it would still drag down the average in older studies that didn’t separate these things out. By filtering out deaths caused by accidents, infections and difficult living conditions, this new study got a much clearer picture of what genetics alone actually contributes.
This matters a lot for anyone trying to understand their own health because it suggests genes play a bigger background role than we’ve given them credit for. It doesn’t mean lifestyle stops mattering, but it does mean genetics deserves a lot more attention than it’s been getting.
There are certain genes that scientists think matter most.
Scientists believe hundreds, maybe even thousands, of genes play some small part in how long we live. Out of all of these, only a handful have actually been properly identified and confirmed through solid research so far.
One example is a gene called APOE, which affects heart health and the chances of developing brain related illnesses later in life. Another is called FOXO3, which plays a role in how the body uses energy, fights off illness, and repairs itself. People who live past 95 years old often carry a particular version of this gene, which has caught a lot of scientific attention.
These genes aren’t exactly magic longevity switches.
It’s tempting to think of genes like FOXO3 as some kind of secret longevity switch, but that’s not quite how they work. They’re not directly responsible for making someone live longer on their own, they’re simply involved in keeping the body’s systems running smoothly for longer, which ends up having the same effect.
Think of it less like a single button that adds years onto your life, and more like a set of background systems that quietly keep everything else working properly. When those systems work well for longer, the body naturally holds up better as time goes on.
Lifestyle and genetics actually work together.
Even with genetics playing such a big role, scientists are clear that your lifespan isn’t locked in from birth. Lifestyle choices still do shape how things play out, working alongside your genes rather than being overpowered by them completely.
There’s a whole area of science called epigenetics that looks at exactly this overlap, studying how daily habits and surroundings can actually change how our genes behave. It’s often described as the way lifestyle choices get under the skin and start influencing the body from the inside.
Scientists are even exploring whether ageing itself can be reversed.
In one striking study involving mice back in 2023, scientists managed to speed up or slow down ageing simply by changing how certain genes were being expressed. This showed just how much power lifestyle and environment really have over the ageing process, even when genetics are involved too.
Findings like this are pushing scientists to ask bigger questions about whether ageing itself could eventually be slowed down or even partly reversed. It’s easy to see why so many wealthy investors and companies have poured money into this area of research, given what it could eventually mean for how long we all get to live.
