Longer lives risk rise of the 'zombie' human
Increasing human lifespan risks creating huge numbers of zombie-like humans - because experts are not close to curing dementia and brain cell loss, a leading scientist has warned.
Mauro Giacca, professor in cardiovascular sciences at King's College London, says keeping the body alive for longer was pointless unless we learned to tackle neurodegeneration and worked out how to regenerate brain cells.
"Why do we age? The short answer is we just don't know," he says. "There are more than 30 theories about why humans age. It is likely there is a biological clock which sets human life around 120 and we are programmed not to live longer than that," he said. "But the probability of undergoing dementia is increasing with the passing of age and the risk we are facing as we trigger regeneration and recover limbs is if we don't find a way to regenerate the brain we will increase the number of perfectly functioning bodies but poorly functioning brains."
Theories about why humans grow old include the "free radical", which suggests that as mitochondria - the cell batteries - burn up oxygen they produce unstable compounds that damage molecules and proteins. But despite claims antioxidants could prevent ageing, no studies have shown a difference.
Ageing may also be caused by senescence, when a cell goes dormant, unable to replicate, but is not cleared out by the body's waste system. Growing older may also be the price of tumour suppression, the killing off of cells before they become cancerous.
The only proven way to prevent ageing is to restrict calories by around two-thirds, which has been shown in animals to extend life span by about 50pc. For humans that would mean potentially living to the age of 180.
"There are people who follow this regime, but it's very difficult. Our brain is wired to search for food," said Prof Giacca. "We lose 80,000 neurons every day, and we haven't yet found a way to regenerate them, so a person who reaches 80 or 90 has already lost about 10 to 15pc of their brain, which is why they think and move more slowly.
"That's before diseases like Alzheimer's... so if you don't deal with those problems you can end up with a healthy heart but a stupid head."