Who wants to live forever? Until recently, the quest to slow ageing or even reverse it was the stuff of legends – or scams. But, today, an evidence-based race to delay or prevent ageing is energising scientists worldwide.

Backed by governments, business, academics and investors in an industry worth $110bn (£82.5bn) – and estimated to be worth $610bn by 2025 – scientists are harnessing the power of genomics and artificial intelligence to extend both life spans and health spans.

Scientists say there are already a number of things we can do to extend life and health, while promising that current and ongoing large-scale trials of drugs and other interventions mean the once-mythical goal of healthy, longer-lived lives is not far away.

“Death is inevitable but ageing is not,” said Dr Nir Barzilai, founding director of the Institute for Aging Research at the Albert Einstein College of Medicine, New York.

Barzilai has almost raised the necessary $50m to launch a five-year clinical trial into metformin, a cheap drug already commonly prescribed for pre-diabetics and diabetics, to prove that it slows cell ageing so dramatically that those who take it can expect to live decades longer, in near-perfect health.

Metformin has already been shown in a number of separate clinical trials to slow the development of most age-related diseases, including all cancers, Alzheimer’s and heart disease. To put it another way, said Barzilai, the drug slows the ageing process. It makes cells and tissues “younger”.

It does have side effects: according to the National Institute for Health and Care Excellence (Nice) guidelines users are likely to suffer stomach upsets and nausea. But, said Barzilai – who has taken metformin for five years for pre-diabetes – “the only long-term side effect is living for longer than your pension lasts”.

The search for extended life and health is particularly active in the UK, where 260 companies, 250 investors, 10 non-profits, and 10 research labs are using the most advanced technologies to hunt for the holy grail. The UK government has even prioritised the separate sectors of AI and longevity by including both of them in the 4 Industrial Strategy Grand Challenges, which aims to put Britain at the forefront of the industries of the future.

Oxford professor Lynne Cox is an expert in the biological mechanisms of ageing and one of the world leaders in developing new ways of stopping cell ageing, otherwise known as cellular senescence.

“As organisms – and people – age, changes build up in their cells that eventually trigger cellular senescence,” she said. “Senescent cells can no longer renew themselves, meaning the ageing body cannot replenish tissue or heal wounds.

“Just over eight years ago, experiments discovered that removing senescent cells from mice led to marked rejuvenation, while transplanting senescent cells into young animals led to premature ageing,” said Cox.

There are now cutting-edge clinical trials in senolytics: the use of molecules to selectively destroy senescent cells in people. Some senolytic compounds are already available online. But, warned Cox, while the research is still in its infancy, a more effective and safer approach is to do what we already know works: exercise, eat better, eat less and sleep well.

Psychologist, neuroscientist and bestselling author of 100 Days to a Younger Brain Dr Sabina Brennan agreed. She isn’t looking to the far horizon for the secret for immortality. Instead, she believes the secret to a healthy old age is to focus on brain health.

“Almost half of adults in the UK cannot name a single risk factor for dementia and despite that 24.6 million people in the UK have a relative or friend living with dementia, one in five people incorrectly believe that dementia is an inevitable part of ageing,” she said.

“But decline in cognitive function is not inevitable in later life,” said Brennan. “A healthy brain can function well in later life, disease is the cause of most decline.

“Alzheimer’s disease, the most common form of dementia, affects 62% of people diagnosed with dementia,” said Brennan. “But the good news is that 30% of all cases of Alzheimer’s disease are attributable to seven modifiable risk factors.”

These risk factors are low levels of educational attainment or mental stimulation, low levels of physical activity, mid-life high blood pressure, type 2 diabetes, mid-life obesity, depression and smoking.

“Avoiding these risk factors won’t just help you defy dementia,” she said. “It will rejuvenate and optimise your brain performance and protect your cognitive functions against injury, stroke and even diseases like multiple sclerosis. You can change your brain at any age and ensure you will live a happier, more independent life for very much longer.”