New Zealanders' life expectancy keeps increasing

Sir Peter Gluckman thinks epigenetics is a key. Photo / Dean Purcell

Start saving for a long retirement. We're going to live far longer if last century's revolutionary changes in health and medicine continue.

Some average New Zealanders' extra years on Earth will be attributable to developments in medical science - the next-generation Herceptin, perhaps, or the perfection of artificially grown liver transplants. Or the eventual introduction of a polypill, or the wider use of statins to reduce cholesterol.

Lifestyle

Much of the anticipated extra life expectancy will be down to lifestyle - good diet, exercise and not smoking.

"We're gaining about a month a year in life expectancy, which is pretty amazing," says Auckland University epidemiologist Professor Rod Jackson.

"I don't think there's any suggestion that it's slowing down. It is driven primarily by reductions in vascular disease, primarily heart attacks and strokes. I don't think there's any indication that there's any kind of upper limit that we can't go beyond."

Life expectancy at birth was 76.3 years for males and 81.1 for females in 2000-2002. A century earlier it was a shade under 60 for males and just over 60 for females.

On the current path, the figures will be 82 for males and 87 for females by 2030. And if, as many hope, tobacco smoking is history by 2020, the seven-year gap in life expectancy between non-Maori and Maori - whose smoking rate is more than twice the national average - will close more rapidly.

Professor Jackson says ending smoking will have a dramatic effect on life expectancy by reducing smoking conditions such as lung cancer and heart disease. "Once you stop everyone smoking you've added on average 10 years to 20 per cent of the adult population. Its a big ticket item."

On the food side, we could gain years by consuming less saturated fat (butter has plenty) and eating a lot of more fruit and vegetables.

By contrast, the contribution of medical breakthroughs to longer lives will be more modest, but exciting.

Epigenetics

The Prime Minister's chief science adviser, Professor Sir Peter Gluckman, the former director of the Liggins Institute at Auckland University, is uneasy about picking what life will look like in 2030.

"I don't think we can assume we are going to have greater life expectancy. People are living in an obeso-genic environment [one which promotes obesity]. We haven't solved the issue of how people should live in an obeso-genic world."

Trying to change the lifestyles of adults and older children is relatively ineffective, he says.

Enter epigenetics - the science of how genetic "switches" that affect adult health are controlled, decades earlier, by environmental factors such as fetal and newborn nutrition.

"It is inevitable the science of epigenetics and pre-natal and early development will be at the heart of preventative medicine," Sir Peter says. "We are two decades, minimum, from knowing how to apply that knowledge to really change people's lives.

"It will lead to healthier lives and will lead to people being less likely to get heart disease, who will age better and more healthily."

The therapies, likely to influence nutrition/metabolism, may be given at birth to the 12 per cent of babies who, because they are born prematurely, are at increased risk of developing type 2 diabetes and cardiovascular disease as adults.

"We injected rats with hormones at birth and we could feed them anything. They never got fat, never got heart disease, never got diabetes. There wasn't anything wrong with them. We could change their destiny.

"I don't think it will be hormones. The next step will be to understand what the hormones do and work out other ways to do it.

"Epigenetics will change the trajectory of one's passage through life."

Fertility treatment

So much for longer life. What about making more babies - or babies that look exactly like ourselves?

Fertility specialist Dr Richard Fisher reckons human cloning will never progress because of insurmountable ethical and political problems.

But he predicts that by 2030, possibly much sooner, a woman's own stem cells - and a man's - will be able to be used to manufacture eggs and sperm respectively. "Older women will be able to have younger eggs. You will still be best to use your own, but there will be an option.

"Genetically they will be identical to you, but they won't have gone through the ageing process."

The consequence will be that for women who can afford the treatment, the biological alarm clock that rings from the 30s, is switched off and they can delay motherhood.