Leading article: There is only one real way to improve public health

Gordon Brown's declaration of intent to turn the NHS from a sickness service to a preventive service is an eye-catching initiative designed to resonate with voters. It was launched yesterday as the first salvo in a new offensive, backed up with copious media appearances, intended to draw a line under the autumn disasters and show that he was back in command of events and prepared to make the hard choices necessary for successful government.

But does the introduction of screening for at-risk patients constitute the kind of "hard choice" that is necessary to promote the nation's health? It is difficult to argue against a strategy of detecting disease early, when the chance of cure is greatest. Intuitively, one would think that it must be a good thing. But once the disease process has started it is, in a sense, already too late. True prevention means targeting the malign influences that not only trigger disease but sustain it. The world today may be a healthier place than it has ever been, but the damaging effect of modern lifestyles means that ours is the first generation in which children may die at a younger age than their parents.

Today's report from the University of Cambridge, investigating the impact of four "healthy" behaviours on average lifespan, shows just how much there is to gain. Professor Kay-Tee Khaw and colleagues calculate that avoiding smoking, taking exercise, drinking moderately and eating five portions of fruit and vegetables a day can add 14 years to your life, compared with someone who does none of these things.

The message is clear: if the Government is really serious about our health it must confront the junk food industry, impose more radical curbs on smoking, and aggressively increase opportunities for walking, cycling and all other forms of exercise. It must change social behaviour, which can only be done by taking on the many vested interests that promote fast food, motoring and alcohol abuse. These are the real hard choices that the Government faces but there is little sign yet that Gordon Brown has the stomach to take them.

It is not only our own health that hangs on the outcome it is the future of the NHS itself. Politicians and the public often talk dismissively of the NHS as a sickness service as a way of highlighting the need for a new focus on prevention. But, first and foremost, a sickness service is what the NHS should be providing a safety net to minister to our needs when we fall ill. And in truth, it struggles to even perform this task adequately at present. The problem is, as Sir Derek Wanless, former adviser on the NHS to Gordon Brown, has pointed out in his updated report on the future of the service, published last September, reducing the burden of avoidable illness on the NHS is the key to providing an affordable service in the future. Unless we find a way to curb soaring rates of obesity, for example, the NHS may not survive even as a sickness service.

This is not to dismiss entirely yesterday's announcement. Expanding screening programmes, or introducing new ones, will make a minor contribution to improving the health of the nation. It may, of course, also increase demand on the NHS by taking up resources to reassure the worried well which might have been better targeted on patients in greater need.

Ultimately, its success will depend on the availability of staff and resources to treat those patients whose disease has been detected. But if this means shifting cash from one part of the NHS budget to another it is unlikely to achieve the goal of improving overall health. As his first initiative of 2008, Mr Brown's promotion of screening as a means to transform the NHS looks like little more than window dressing.