Nell Townsend, who celebrated her 100th birthday in January, has a smooth, creamy complexion and beautifully manicured scarlet nails. She dresses smartly and refuses to wear flat-heeled shoes. “I wouldn’t mind living to 150 if I looked okay and was in good health,” she says. “But I’m dying from the feet up, love.”

We both burst out laughing. Now a centenarian, she still doesn’t need glasses or a hearing aid and her mind is as sharp as a tack. Until three years ago, she drove a car and often went to the races. Eighteen months ago she considered wearing black leather pants to her granddaughter’s wedding but settled on something more conservative.

She misses the races, and reminds me that the autumn racing carnival is almost here. “I’ve come in here too soon,” she sighs, referring to the luxury convalescent hospital she entered at 98. Until then she lived alone, but her increasingly frequent falls made it dangerous to stay in her two-storey home.

I attended Nell’s 100th birthday party the week Joe Hockey announced changes in Medicare pensions were needed because in the future people could live to be 150. Six weeks later, I celebrated the centenary of another woman I know. When I thought about it, I was astonished at the number of centenarians and near-centenarians I knew. Last year the mother of one friend and the father of another both died at the age of 104, and the mother of another friend died recently aged 100. Three of my friends have parents who will soon turn 100.

When asked the secret of his longevity, he quipped, “Red wine and wild women.”

Lionel Cohen, who died 18 months ago at 104, lived alone, cooked his own meals, always looked immaculate and passed his driving tests. He had lost his hearing but not his sense of humour, and when asked the secret of his longevity, he quipped, “Red wine and wild women.”

Once a congratulatory telegram from the Queen was a rare event, but today there are about 4000 centenarians in Australia. By 2030 it is estimated that their number will rise to 6300. By 2050, that figure will be almost 19,000. A baby born today has a 30 per cent chance of living to 100.

No wonder researchers are talking of a longevity revolution.

Dr John McCormack, senior lecturer in health and geriatrics at La Trobe University in Melbourne, is the author of The Longevity Revolution: the Emergence of Centenarians and Super-Centenarians in Australia. “When I wrote my first article on the subject of longevity in 1995, we didn’t know how many centenarians we had,” he says. “Today we have three categories: centenarians, 100 to 104; semi-super-centenarians, 105 to 109; and super-centenarians, 110 or over.”

Australia ranks among the 10 countries with the highest number of centenarians per capita of population. The oldest Australian is a 112-year-old woman in Blackburn in Victoria, while the oldest person in the world today is a 116-year-old woman in Japan.

A major study of centenarians conducted at the centre for healthy brain ageing (CHeBA) at the University of New South Wales recruited 350 participants. According to Perminder Sachdev, professor of neuropsychiatry and co-director of CHeBA, the study aimed to assess which participants were cognitively intact and how they differed from those who developed dementia. “We also wanted to look at risk and preventive factors, and to take DNA from their blood samples to map their genome and look at markers of change or variation,” he says.

The study wound up last year and the data is currently being analysed, but it dispelled the myth that dementia, disability and disease were inevitable in old age. About half of the participants, who ranged from 95 to 111, were functioning physically and mentally, and most were still living in the community. Among them was Dorothy Delow, a sprightly 101-year-old, who was the world’s oldest table tennis player.

Dr Charlene Levitan, an associate lecturer at UNSW, co-ordinated the centenarian study. “We are looking for the key to successful ageing to determine the genetic and environmental factors that contribute to longevity so we can all live longer and lead healthier lives,” she says. “But the aim of our research is to add life to years, not years to life.”

Scientists estimate that genes are 30 per cent responsible for longevity. Sachdev is currently conducting an Older Australian Twin Study, looking at 600 twins over 65 in NSW, Victoria and Queensland. Half of the twins are identical and half fraternal. “Twins are a great source of determining if traits are genetic or environmental, and we are doing a four-year follow-up to assess how much is due to genes or to lifestyle factors.’’

There’s no doubt that lifestyle affects longevity. Most researchers emphasise the importance of diet, exercise and social networks. The 130 centenarians McCormack surveyed had two things in common: they had worked hard all their lives and they weren’t overweight. That’s true of Nell Townsend who worked first in her parents’ sandwich shop, then in her husband’s bakery, loading up the carts with bread. Later, when they had a Holden dealership, she used to drive across Sydney delivering the cars from Pagewood to Blacktown. In between, she brought up four children.

Most studies reveal that female centenarians outnumber men at least three to one, and it has been suggested that women tend to take care of themselves better than men. When I ask Nell for the secret of her longevity, she says, “I always looked after myself with regular massages, manicures and pedicures. I never smoked, drank or ate much meat. Maybe my secret is eating salt, sugar and butter.”

Recent research indicates that low protein intake may be a major factor in longevity. A study at the Charles Perkins centre at the University of Sydney looked at the life spans of 900 mice on diets containing varying levels of protein, carbohydrates and fat. Mice on a low-protein, low-fat, high-carbohydrate diet lived significantly longer. The researchers believe this has enormous implication for what and how much we eat, on our health, and ultimately on the duration of our lives.

Like diet, personality is also considered to be an important factor in longevity. A study of 660 people in Ohio in 1975 looked at their attitudes to ageing and their survival rates 23 years later. Yale University’s Dr Becca Levy, who headed the later research team, found that those who had positive perceptions of ageing lived on average 7.5 years longer, a bigger increase than that associated with exercising or not smoking.

According to most studies, centenarians tend to be positive, optimistic, resilient and able to cope with loss, which is crucial at an age when their spouses, friends and even children have died. Lilly Kaufmann, who will turn 100 in four months, is a textbook example of the power of personality and attitude in dealing with life’s problems. Her genes are good, too: her own mother lived to 97.

“I’ve always been so lucky,” says this Holocaust survivor who struggled to survive in Hungary with her small daughter after her first husband and many close relatives had been killed. Since arriving in Australia, she has rebuilt her life, working 16 hours a day with her second husband in his factory. “I was never depressed, always positive,” she says. “I don’t judge people, I accept them.”

Widowed many years ago, Lilly lives in her apartment with a carer, attends seniors’ clubs four days a week and welcomes visitors with a big smile. As she is hard of hearing, her daughter Susie translates my questions into Hungarian.

“My mother is a good, generous human being. The word ‘no’ doesn’t exist in her vocabulary,” Susie says as they begin to play rummy tiles, a game they play every week. When I comment on the speed and accuracy with which Lilly places the tiles, Susie tells me proudly that her mother usually wins, but Lilly demurs. “I don’t mind if I win or lose, darling. I just like to play.”

With the proliferation of studies into longevity around the world, new factors are emerging all the time. An oft-cited 25-year study conducted by Duke University medical centre in North Carolina, for instance, concluded in 1982 that an active sex life can increase life by four years.

Dr Stuart Jay Olshansky of the University of Illinois is a passionate proponent of what he calls the “Longevity Dividend”. He believes that extending the length of healthy life by slowing down the ageing process is a scientifically plausible goal, and he calls on governments and healthcare organisations worldwide to invest in preventive medicine and public health. The dividend would be that by living longer and staying physically and mentally healthy, older people could remain in the workforce longer, amass more income and savings, and relieve pressure on Medicare and other age-based programs.

That’s a dividend Joe Hockey would probably like to see.

Before leaving Lilly Kaufmann, I ask why she thinks she has lived so long. “There’s no secret,’’ she says. “God wanted it.” Would she like to live to 150? “Why not?” she says. “I feel well and nothing hurts. I enjoy seeing my family, watching TV and reading.”

And as we leave she opens a romance novel by her favourite author, Danielle Steel.