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Increasing life expectancy has been one of the wonders of the last century or so.

Throughout the 1800s it hovered around the 40 years of age mark in the UK, but since the start of the 20th Century it has almost doubled.

This can be put down to a number of factors including improved health care, sanitation, immunisations, access to clean running water and better nutrition.

It means about a third of babies born today can expect to celebrate their 100th birthday.

But are we thinking about the issue in the right way?

Ministers have responded to the challenge of the ageing population by increasing the age at which people qualify for the state pension to 68 in future years.

This has been done to maintain the ratio of working-age adults to pensioners.

At the moment there are 3.7 20 to 64-year-olds for every person over 65.

If the current trend in life expectancy continues, by 2050 it will be down to 2 to 1.

It will come as no surprise that increasing working lives to 68 almost completely counteracts this.

But it is not quite as simple as that.

People can only work if they remain in good health - and currently the average "healthy life expectancy" is 63.5 years of age, according to the Office for National Statistics.

The problem is that a rise in life expectancy does not automatically lead to a similar rise in years spent in reasonable health.

Over the last 20 years the gap has been getting wider. Life expectancy has risen by 4.6%, but healthy life by only 3%.

So what can be done about it?

It is an issue that is being explored by the , a think tank led by Baroness Sally Greengross, who recently chaired a House of Lords committee.

Prof Les Mayhew, of the Cass Business School, who acts as an adviser for the centre, believes the answer lies not in improving health care, but in investing in prevention and early intervention.

"That means addressing lifestyles, but also giving people the right support to stay healthy and independent. Social care will be critical.

"If we are not careful we will just end up in a situation where instead of people retiring there will just be more on incapacity benefit."

To stress his point, Prof Mayhew has carried out modelling, which shows the importance of healthy life expectancy.

He looked at various scenarios to see what effect they would have on GDP.

It shows that by far the most important factor in terms of encouraging economic growth is expanding healthy working lives by a year.

If that could be achieved, GDP would grow by 2.7% compared with 1.6% for increasing the numbers working by 1% and the 1% boost gained from a 1% increase in productivity.

Understandably, the government maintains it is taking improving the health of the nation and supporting older people seriously.

Just last week ministers in England announced more details about how the cap on elderly care costs will work.

Meanwhile, a national organisation - Public Health England - has been created to encourage lifestyle changes and councils have been given ring-fenced budgets to spend on public health schemes.

Nonetheless, in light of the recent apparent U-turns on plain packaging for cigarettes and the minimum pricing for alcohol, the suspicion persists that not enough is being done.

Prof Michael Murphy, an expert in demography from the London School of Economics, says: "Although healthy ageing and well-being are on the political agenda, actions so far have been limited."