Want to live up to 100? Follow tips...

They say that if you follow the simple rules, you have a fair chance of joining the growing number of centenarians across the globe.

The scientists estimate that the largest centenarian populations in 2050 would be in China with 472,000, the US with 298,000, Japan with 272,000 and India with 111,000.

In new research published in New Scientist, scientists have drawn the list of 10 commandments after trawling through medical studies published over the past 50 years examining why more people are living longer.

The conclusion is that taking good care of the physical lifestyle - food, exercise - is a small part of the trick. Some scientists believe that spiritual and social reasons can be more important.

Psychology and health expert Carey Cooper, from Lancaster University, said positive thinking was one of the most important factors running throughout the 10 rules.

Taking good care of the physical lifestyle - food, exercise - is a small part of the trick for a longer life. Some scientists believe that spiritual and social reasons can be more important. "We're rushing around all the time and don't really have the moments when we can do something for ourselves. If that means sharing a piece of chocolate with a loved one, so be it. It's not going to do you any harm and will help you relax and enjoy life," he told the Daily Express.

He added: "Marriage and having a stable relationship is one of the most important factors. A long-term relationship provides you with structure and stability in a world that's ever-changing."

The New Scientist article, titled "How To Live To 100 And Enjoy It", says that the first rule for longer life is exposure to certain 'poisons' that may help to reverse the ageing process and boost life expectancy by up to 15 years.

The article said that small doses of "stressors" normally considered dangerous to humans could actually aid the body's self-repair system and prolong life. Scientists included X-rays and mild sunburn cases as possible positive factors in the phenomenon known as "hormesis".

The second commandment is remaining sociable, with a happy marriage and good family life being essential for health.

Studies have shown that marriage can add as much as seven years to a man's life and two years to a woman's life.

The place where you live is the third rule: there are several places across the globe that are conducive to man living up to the age of 100.

For example, the Japanese island of Okinawa is generally considered the longevity capital of the world, with more than 400 centenarians in a population of 1.3 million.

The fourth rule is that so-called vices such as chocolate and sleep have a good effect because a little of what you like can do you good rather than harm.

The fifth rule says you should exercise the brain to stay active - play Sudoku, for example.

The sixth commandment follows the age-old adage that prevention is better than cure, urging aspiring centenarians to go for cancer scans if there was a history of the disease in the family.

The seventh rule is simple: watch what you eat.

Rule eight urges people to put more excitement into their lives. Merely living longer is not worth doing unless it is an enjoyable experience.

Rule nine advises those seeking a long life to embrace any new technologies.

The final commandment is to smile and feel happier with one's lot in life.