While most of us can expect to live to around 80, some people defy expectations and live to be over 100. The oldest person in history is a French woman named Jeanne Calment who lived till 122. When she was born in 1875, the average life expectancy was roughly 43.
How long can a human being live? A recent study proposes that the limit of the human lifespan is closer to 150, almost 23 per cent higher than what Mrs Calment lived to see. But we are far from making the study’s proposal a reality.
The most reliable method for calculating life expectancy, and thus lifespan, relies on the Gompertz function. Developed in the 19th century, this function stated that human death rates increase with age. This means that your chances of dying from cancer and other serious diseases roughly doubles every eight to nine years.
Gompertz calculations can also calculate health insurance premiums. That is why insurance companies take interest in your possible smoking habit, marital status or something else that should help them make an approximate assessment of your lifespan.
Another way to assess our lifespan is to observe how our organs decline with age. For example, eye function, and oxygen usage while exercising tend to decline with ageing. Most calculations indicate organs only function until the average person is around 120 years of age.
These studies also reveal the increasing variation between people as they grow older. Now researchers in Singapore, Russia, and the US have found a different approach to estimate the maximum human lifespan. Using a computer model, they estimated that the limit of human lifespan is about 150 years.
Living till 150
The researchers took blood samples from over 70,000 participants, aged up to 85, and looked at short-term changes in their blood cell counts to conduct the modelling study. The number of white blood cells a person had indicated the level of inflammation in their body, while the volume of red blood cells indicated a risk of a heart condition or any cognitive impairment such as memory loss.
The researchers then simplified this data into a single parameter called the dynamic organisms state indicator (Dosi). Changes in Dosi values across the participants predicted whose health would debilitate with age, how this varied from person to person and modelled non-resilience with age. These calculations predicted that a human body’s resilience would fail at 150.
But such estimates assume no new medical treatments will be found for common diseases. The estimate is flawed since significant progress occurs over a lifetime and this benefits some people more than others.
A baby born today can rely on about 85 years of medical progress to enhance their life expectancy, while an 85-year-old alive needs to stick to current medical technologies. So, lifespan is easier to calculate for older people.
Good genes, a healthy lifestyle and medical developments in ageing would help a person live till 150 years. Currently, our inadequate understanding of the biology of ageing stops us from increasing our lifespan.
With the current pace of progress, the average person will not live to see 150 for another three centuries.