Leading article: A happy summer for the health police

Bank holidays, as any city dweller knows, are best spent at home. Streets are deserted, supermarket queues are short and a delicious quiet descends as the neighbours head for the country and the beach. Now doctors have offered an extra reason for eschewing the sybaritic delights of Clacton or Clitheroe. Going away can be bad for the heart.

Hours spent in a hot tin can jammed in a line of hot tin cans, diesel fumes mingling with the aroma of marmite sandwiches and bruised bananas while fractious kids demand "Are we there, yet?" from the back ought to make anyone ill. Now the British Heart Foundation has unnecessarily warned that the combination of travel, hot weather and air pollution can spell danger for those "intent on fun". Amazing.

It has been a bumper summer for the health police. We have had warnings about the sun, the air, and the sea, about impurities in drinking water, E coli 0157 and nerve damage caused by vitamins (B6). But outdoing all these have been warnings about the heart.

Within the space of six weeks, at least half a dozen theories about the causes of heart disease and heart attacks have been offered by scientists. The proliferation of theories and estimates of risk leave the average reader floundering, wondering whether to change jobs, spouse, diet or holiday plans. Scientifically, there may be nothing to fault. But in public health terms it is a disaster. Any bar-room medic trying to assess the competing arguments can only conclude that doctors are as ignorant as the rest of us - and mine's a pint, a greasy bacon sarnie and a packet of 20 please, guv.

A striking example of the difficulties the public face occurred last month. On 23 July, the National Heart Forum called a press conference to highlight Britain's poor record on heart disease measured against comparable countries and to reinforce the message on diet, exercise and smoking. These three, the experts said, accounted for most of the variation in heart disease rates and there was no other factor, either known or likely to be discovered, that had an impact of a similar magnitude on the risk.

Yet the following day, a paper in The Lancet, the latest in a series to emerge from a 20-year examination of 10,000 civil servants known as the Whitehall study, showed bosses who have control over their work are less likely to suffer heart attacks than workers who don't. Those on the top floor were healthier than those on the shop floor and it was the degree of participation in decisions that accounted for most of the difference.

Reconciling these two views of the causes of heart disease demands an appreciation of relative risk. Comparing overfed, understretched (in a physical sense) Westerners with their lean, active cousins in the developing world leaves no doubt about the importance of the traditional risk factors of diet, exercise and smoking. But within Western nations, differences persist between groups. When comparing British executives with British clerks, job control appears to account for almost half the variation of heart attack risk - but that is a small difference compared to the benefit (in heart disease terms) of being born in, say, Uganda.

That is only the start of the confusion. This week, researchers reported that submissive women have one third of the risk of suffering an attack compared with those who are more assertive. Earlier research has shown that aggressive, ambitious Type A personalities are more prone to attacks than relaxed Type B ones. Next week a new study will suggest that men who give blood reduce their risk by depleting their iron stores - in the same way that women do naturally through menstruation. Red wine, what your mother ate during pregnancy, and infection have also been implicated.

So, where does that leave us? Meek, non-smoking blood donors who run their own lives, eat up their greens and cycle to work shall live long enough to inherit the earth - while the rest of us enjoy life, ignore the health advice, and die young.

Science offers no simple answers. We have to learn to live with uncertainty and accept that scientific understanding proceeds like football - with much, apparently purposeless, running around punctured by occasional flashes of brilliance that move the game forward.

The drawback is that this leaves openings for those who wish to exploit the uncertainty for their own commercial advantage. Yesterday, David Bacon, head of corporate communication at British American Tobacco, sought to muddy the clear message on smoking delivered a day earlier by Geoffrey Bible, the chairman and chief executive of the US tobacco giant Philip Morris, that cigarettes "might have" killed 100,000 Americans.

In a piece of sophistry of the sort we have come to expect from the tobacco industry, Mr Bacon sought to represent this historic admission as no more than an observation about the statistical link between smoking and lung cancer. He claimed the disease's biological cause had "still to be established".

Technically he may be right, but morally his position is bankrupt. There can be no doubt about the lethal nature of cigarettes yet this message is still being fudged three decades after it became a certainty.

On the major issues of public health - smoking, heart disease, cancer - where there is a measure of agreement, we need scientists to sign up to the basic thesis rather than squabbling over the finer points. Scientific accuracy demands an assessment both of the strength of the evidence and of the power of the conclusion. Facts are not sacred, they require interpretation.