Want to live to 100? The Australia's centenarians have been quizzed to uncover the secrets of long life.

Alcohol is not totally ruled out, says Professor Robyn Richmond, but smoking is and maintaining a healthy and stable weight is vital.

Positive outlook

A positive outlook is key while it also helps to be female, as only 25 per cent of Australians aged over 100 are men.

"Even if you have one drink (a day) and drink within safe levels you're fine," said Prof Richmond from the University of NSW and director of the Australian Centenarian Study.

"Notice that none had risky alcohol use ... so it's still OK to have a drink."

Prof Richmond and fellow researchers conducted face-to-face interviews and took biometric measurements from 188 Australians aged 100 and over.

Many spoke of having siblings or relatives who also lived to a ripe old age though Prof Richmond said genes only accounted for about 20 to 30 per cent of their longevity.

She said the collection of diet, personal outlook and social and environmental factors made a more significant contribution to long life.

"Even if you have got bad genes but you live a healthy life and stay positive, you could still have a very long life," Prof Richmond said.

Avoiding isolation was important, as 88 per cent of the centenarians said they had contact with their family at least once a week while 76 per cent took part in regular group activities.

Ninety per cent of the centenarians were widowed or married while 10 per cent were separated or divorced, or had never married.

Half (49 per cent) were current drinkers in moderation, while 38 per cent were teetotallers.

There were two current smokers among the group while 28 per cent were former smokers.

Prof Richmond said none were obese and, importantly, they commonly reported having a stable and healthy weight throughout their life.

Sixty per cent said they still went on regular walks or were otherwise active.

"When they reflected on past behaviour ... in their 30s to 50s they had low neuroticism and were low on fear, low on anger, they weren't hostile to others," Prof Richmond also said.

"They were high in extroversion and were conscientious, including dutifully following a doctor's advice."

The centenarians also reported low levels of mental ill health and a common ethos of adapting to change and not "internalising stressful events".

Australia among the world's highest proportion of centenarians

Prof Richmond said Australia had among the world's highest proportion of centenarians - along with the US, Norway, Sardinia and the Japanese islands of Okinawa - and the number was growing.

Australian centenarians have roughly doubled in number every decade from 443 in 1981 to 1268 in 1991 and 2297 in 2001.

In 2006, there were 3154 centenarians and Prof Richmond said this was expected to hit 12,000 by 2020.

"That's a lot of cards coming from the Queen and the governor-general," she said.

Prof Richmond presented the research results on Tuesday at the International Federation on Ageing conference under way in Melbourne.