If you want to live to a ripe old age, it’s not just about eating five a day and stopping smoking.
Actually, that's not the whole story. Scientists have found recently that, while looking after your physical health is important, those who live to a ripe old age tend to have other things going for them. In a nutshell, their outlook and personalities set them up for longer life.
Happily, you can take some of these happy traits on board, so read on for the real secrets of the ancients.
What psychologists and scientists have discovered over the last few years is something that might be described as the meaning of life. We don't mean that in any spiritual way. But it seems that evolution has given a longevity advantage to people who are nice to others.
There's plenty of raw data to back that up. One study found that older people who volunteered regularly had a massive 44 per cent lower chance of dying from any cause than those who didn't volunteer at all. That was even true after factors like smoking, exercise and general physical health were taken into account.
To put this finding into context, that means volunteering is as good for your health as regular exercise and almost as good as giving up smoking.
Why might that be? Scientists talk of a 'helper's high', a physical sensation of well being that we get after doing a good deed (note that further studies have shown the good need doesn't need to be volunteering, it can mean helping an elderly neighbour with her shopping or even just giving up your seat on a bus). It's similar to the high that you get after exercise, but it lasts longer.
In another study, the helper's high was responsible for half of participants feeling calmer, more energised and better about themselves after helping others. If you feel good about yourself, you have more reason to live for a long time.
The famous Mayo clinic in America described optimism like this: "Optimism is the belief that good things will happen to you and that negative events are temporary setbacks to be overcome."
If that describes you, you may get a physical advantage from seeing the world in such a positive light. In one study, pessimists had a higher risk of death over a 30-year period than optimists. Optimists may just have more will to live, or they may be more determined to look after their health because life is so good. Either way, they win out in the long life stakes.
And in May the Albert Einstein College of Medicine in New York published research into 243 centenarians which found one common trait they all shared was a positive outlook. "When we assessed the personalities of these 243 centenarians, we found qualities that clearly reflect a positive attitude towards life," said lead researcher Nir Barzilai.
The problem is, you're either an optimist or you aren't. You can't learn optimism. Or can you?
Suzanne Segerstrom, a professor of psychology at the University of Kentucky, thinks even adults may be able to become more optimistic. "People can learn to be more optimistic by acting as if they were more optimistic," she writes in her book Breaking Murphy's Law.
She argues that if you act like an optimist which means attacking problems head on, staying focused on your goals and getting advice when necessary (rather than giving up and walking away) you'll eventually become one. When you become one, you'll get all the longevity advantages that optimism brings with it.
But don't be happy all the time
Optimism is not the same as happiness, and of course happiness is what we're all looking for. But June Gruber, a professor of psychology at Yale University, has found that there is such a thing as too much happiness.
Too much happiness can lead to risk taking, like drinking and eating too much, she says. Other researchers have found that being sad, for some of the time, is good for us, because it can make us think through our problems properly and in more detail.
So if you want to live a long time, your best bet is to be optimistic about the future, but not sky-high happy all the time.
It may seem like a lame excuse for going down to the pub again, but being sociable is probably as important to your chances of living to 100 as cutting booze. Recent research by Julianne Holt-Lunstad of Brigham Young University in the US has added to a wealth of evidence on the benefits of having a close circle of friends.
According to Holt-Lunstad's report: "Individuals with adequate social relationships have a 50 per cent greater likelihood of survival compared to those with poor or insufficient social relationships. The magnitude of this effect is comparable with stopping smoking and exceeds many well known risk factors for mortality such as obesity and physical inactivity."
The effect may be even more pronounced in men, according to another US study. It found that antisocial men die younger than their more outgoing counterparts because they tend to get heart disease earlier.
The study adds that antisocial men may have an inbuilt anger that leads to high blood pressure.
How to live to 100
What all this suggests is that, though important, keeping physically healthy is only one piece in the jigsaw that leads to a long life. Being optimistic, sociable and generous to others appear to be at least as important as eating five-a-day or exercising regularly. Luckily, they're traits that we can all to some extent adopt.