New research shows that people with 'conscientious' personalities can expect to live longer.
Are you the sort to give up your seat on the bus to an elderly person and cover for a colleague who took a long lunch hour? Do you believe in pushing yourself to the limit and take pains over your work? If so you could end up living longer than your more selfish and less dedicated fellows.

New research from the longest-running psychology research programme in the world - it started in 1921 - is providing fascinating evidence that there is a personality type that seems to be linked with a longer and healthier life. The results are surprising and run counter to many established theories about personality and health.

"The connection is about as strong as that between cholesterol levels and longevity," says Dr Howard Friedman of the University of California, Riverside. "If a connection this strong had come up between, say, a pesticide and reduced life expectancy you'd have a major health scare on your hands."

It was over 70 years ago that Dr Lewis Terman selected 1,528 Californian boys and girls, gave them extensive personality tests and gathered their biographical details and then conducted follow-up interviews throughout their lives. "They were known as the Termites," says Dr Friedman. "About half of them are dead now so they provide a unique database to see what personality types and what sorts of early experience can predict later health. And because they were all chosen on the basis of having a high IQ - at least 135 - their health is less likely to be affected by other factors such as poor diet or having nowhere to exercise," he says.

Two factors turn out to be particularly influential in affecting life expectancy. The first is how high they rate on the personality trait known as "conscientiousness". The second is whether their parents were divorced. "We knew that divorce can affect children in the short term," says Dr Friedman, "but this is the first clear evidence that it has such a long- term effect."

The research shows that on average, male Termites whose parents had been divorced died at 76, while those whose parents stayed together survived until 80. The corresponding ages for women were 82 and 86. "They only had a divorce rate of 13 per cent. Today the rate is nearly four times that. If divorce was a type of food it would rate as a major health hazard," he says.

The study also showed that the old adage about getting married for the sake of your health is true, but only if you have a stable relationship. To have your marriage break up is more damaging than not getting married at all. In fact, in health terms, staying single is as beneficial as a happy marriage.

The study made further surprising discoveries, particularly where the idea of a conscientious personality comes into play. For instance, many life-style gurus claim that an optimistic outlook contributes to long-term health, but among the Termites the happy-go-lucky types didn't have a very good survival rate. Not only that, the introverted, socially insecure kids, often picked out in other studies as being prone to health problems, actually proved very resilient. Many went on to be scientists.

Dr Friedman is well aware that linking personality to illness is a tricky business. It is an idea that goes back to the Greeks, but modern scientific medicine has been rather sceptical of it, not least because of the difficulty in agreeing on how to measure personality. Perhaps the most enthusiastic advocate of the idea is the maverick London-based psychologist Dr Hans Eysenck, who has claimed strong connections between introverted, repressed personalities and cancer, and hard-driven extroverts and heart disease. The problem is that many other researchers do not agree with him. In fact, his work has been the subject of bitter debate in leading medical journals.

"We haven't found any link with specific diseases," says Dr Friedman, "but we have found a clear link between what Terman called 'conscientiousness' - being truthful, prudent, conscientious and not vain - and longevity. Children with high rates of 'conscientiousness' at the age of 11 lived significantly longer. In any given year of their life they were 30 per cent less likely to die than Termites with a low rating - about the same level of risk that high blood pressure contributes to heart disease.

So why have these conscientious kids been outliving their peers? The obvious answer - that they are more careful - is part of it, but that's not the whole story. "These types are slightly less likely to smoke and drink, but not that much," says Dr Friedman. "You might think that they'd take fewer risks, but analysis showed that they were only slightly less likely to suffer from accidents than the rest of the bunch."

It certainly wasn't because they were usually cheerful. The popular idea that there is a link between optimism and having a sense of humour and living to a good age certainly didn't stand up. In fact, cheerful kids who weren't conscientious grew into adults who died younger - about 25 per cent increased risk in any year - because they were also more likely to drink, smoke and take risks. It seems that cheerfulness is a good way of dealing with stress in the short term but it leads to careless behaviour in the long run.

Dr Friedman suggests that there could be some underlying physiological factor but he hasn't found it. Instead he opts for the more mundane explanation that these honest, loyal and helpful children were more likely to behave in healthy ways as adults. When things got stressful they would therefore be more likely to do something about it or to have already taken precautions - you'd be unlikely to find them without insurance, for instance. What's more, they would be more likely to have stable marriages and a network of friends.

Until now, one of the most reliable markers of life-expectancy has been sex because women live considerably longer than men. "The fact that a combination of divorce and the conscientious personality is as accurate as gender in predicting longevity is dramatic evidence of the importance of these findings," says Dr Friedman. Termites who scored low on conscientiousness and whose parents divorced, died on average at 74, while the high scorers who came from an unbroken family survived to 81. Similar to the male-female difference.

"Common wisdom might suggest that a selfish self-indulgent boor may prosper by stepping on others," says Dr Friedman. "But when it comes to a long life the encouraging news is that good guys finish last."