A day after the 2015 Intergenerational Report projected Australia would have almost nine times the number of 100-year-olds we have today, and well over 300 times the 120 or so centenarians we had 40 years ago, Mr Lederer said attitude was key to enjoying advanced age.

"It's no good moaning and groaning; you don't know how long you've got so just make the most of it," the Canberra resident, who celebrated his 100th birthday last October, said.

"Life is full of variety. I've got the flu at the moment. I'm feeling cold and shivery and I've got a runny nose. But I expect that in two or three days that will have passed and I will be very much enjoying life again."

According to the report, in 40 years time the ranks of Australians aged 85 years or over are projected to quadruple from today's number to two million, and will represent almost 5 per cent of the population, up from 2 per cent today.

While the report projects life expectancy will rise only modestly over the next 40 years, to 95 for men and almost 97 for women, it raises the possibility of medical breakthroughs lifting life expectancy above 140 years.

A former World War II intelligence specialist and property company executive, Mr Lederer lives at home with his wife, Tina, her sister and a new puppy, Buddy. He takes a keen interest in current events and passes his time doing crosswords.

"The challenge keeps my mind awake," he said.

An advocate of always looking on the bright side of life, Mr Lederer praised the often maligned Canberra climate and said he was lucky to have lived in the national capital for the past 42 years.

"Look at this country," he said. "Last year half of it was in a drought and half of it was under water. We had none of that here."

Another source of happiness was Buddy, the puppy who arrived in the house a few weeks ahead of his 100th birthday.

"He's actually a blessed nuisance," he said. "Buddy has brought me a lot of joy but I'd be even happier if he was less destructive. He chewed up my hearing aid last week."

Asked what advice he would give to future centenarians, Mr Lederer stressed the need to accept whatever may come.

"Don't say this is how something should be or how you would like it to be," he said. "Accept it for what it is and make the most of it."

And regrets? He's had a few, but not too few to mention.

"I was a fool," he said; "I was mad on the horses. I should have forgotten the horses and concentrated on meeting people who could teach me things."