HOW TO LIVE TO BE 100
The world’s oldest person, Emma Morano, died earlier this month, at the age of 117. But very long lives are no longer a rarity
How much has longevity increased?
Most babies born in 1900 did not live past 50. Today, according to the World Health Organisation (WHO), the average global life expectancy at birth is 71.4. Of course, this figure conceals wide national variations, from the lowest (50.1 in Sierra Leone) to the highest (83.7 in Japan), and between men and women (69.1 and 73.8 respectively worldwide). But the dramatic increase in life expectancy across the globe during the 20th century ranks as one of humankind’s greatest achievements. The fastest gains have been made in East Asia, where life expectancy has increased from less than 45 in 1950 to more than 74 today.
Why has this happened?
Initially, life expectancy jumped as a result of so many more children living to adulthood; not because more adults lived to old age. This was predominantly due to the public health projects of the 20th century – the immunising of millions against smallpox, polio and measles, for example – and also to the spread of more nutritious diets, and cleaner drinking water, which reduced serious infections among children. More recently, though, mortality rates have begun to decline greatly among older people, due largely to medical advances and better health education. Today, the elderly are, in most countries, the fastest growing part of the population (see box). In the developed – and much of the developing – world, chronic and degenerative diseases (heart disease, stroke, diabetes, dementia) have overtaken infectious and parasitic diseases as the leading causes of death.
Where do people live longest?
Mostly in rich industrialised nations with good healthcare systems: in Western Europe, Israel, Japan, South Korea, Australia and New Zealand. Britain has a respectable life expectancy of 81.2; in the United States it is 79.3, about the same as Cuba, Costa Rica and the Czech Republic. But demographers and public health experts have also isolated specific regions where longevity is greatest. In the 1950s, the US physiologist Ancel Keys observed that southern Italy had among the world’s highest concentration of centenarians, and identified the health benefits of the Mediterranean diet: fresh fruit and vegetables, fish and olive oil, with little meat and animal fat. Keys himself moved to the Cilento peninsula, south of Naples. He died in 2004, aged 100. More recently a number of other “blue zones” – areas where people live longest statistically – have been identified.
Where are these blue zones?
They include the islands of Okinawa in Japan, Sardinia in Italy, and Ikaria in Greece. According to the journalist Dan Buettner, who has written widely on the subject, the zones share various “general trends”: their inhabitants eat a plant-based diet (a love of beans is one common denominator); they tend to walk a lot, and to grow their own herbs and vegetables; and they have a strong sense of community. Eating nuts, an active sex life and a moderate alcohol intake also seem to help. In the US, he identified a “cultural”, rather than geographical, blue zone: the community of Seventh-day Adventists in Loma Linda, California, follow a Bible-inspired vegetarian diet and have a life expectancy some ten years higher than that of other Americans. In all these blue zones, old people also remain far healthier: heart disease, dementia and other diseases of old age are much rarer. Even outside such zones, however, people are generally living longer.
How much longer?
Between 1840 and 2007, life expectancy in the West increased by an average of three months per year; two-and-a-half years per decade. The Office for National Statistics projects that in the UK, it will rise to 83.4 years for men, and 86.7 for women, by 2032; the number of centenarians is expected to increase tenfold by 2050. The upper limit of a possible lifespan seems still to be around 120; the oldest verified person ever is the Frenchwoman Jeanne Calment, who died in 1997, aged 122.
Can we expect this upper limit to be lifted?
Probably. The general view among gerontologists is that ageing is a product of evolutionary neglect, not evolutionary intent: we are designed to live long enough to pass on our genes, and genes that have ill effects later in life aren’t exposed to the pressure of natural selection. However, in safe, predator-free environments, nature does seem to invest in longevity and in ensuring a longer span of reproductive capability. The Greenland shark can live for 500 years; the Galapagos giant tortoise can live past 150. So there’s no absolute scientific reason ageing shouldn’t be arrested – and the attendant deadly diseases staved off.
Are scientists working on how to arrest ageing?
Yes. Experiments have shown that by significantly restricting the calorie intake of mice and rats, their lives can be extended by about 40%; similar experiments have also worked with our close relative the rhesus monkey. It’s unclear why, but it seems that under the strain of coping with reduced food levels, the body spends more time repairing cells and increasing resilience. Of course, this is hard to replicate: these animals have had their diets restricted since birth; starving yourself later in life doesn’t work in the same way. However, scientists are trying to create treatments to synthesise this effect.
Could ageing be halted entirely?
Some gerontolgists, notably on the west coast of America, think life could be sustained almost indefinitely. Aubrey de Grey, of the Sens Research Foundation in Silicon Valley, argues that if the seven main types of damage caused by ageing – such as DNA mutations and cellular loss – could be reversed, we would be on course to live for 1,000 years. Others argue that this is true in principle, but is rather like saying: “All we have to do to travel to another solar system is these seven things: first, accelerate your rocket to three-quarters of the speed of light…” For now, the best bet is probably to eat a Mediterranean-style diet, walk a lot, keep in touch with friends and do a little gardening.