There have been five major multiple risk factor intervention trials, all of which were in middle aged men. The duration of follow up was between five and twelve years. The risk factors which were altered by intervention were diet, smoking and blood pressure; in two studies, attempts were also made to reduce weight and increase exercise.

Some studies have examined the effects of drugs or diet alone (that is, the standard World Health Organization recommendation of limiting fat intake to 30 per cent of total dietary intake, with no more than 10 per cent each of saturated, polyunsaturated and monounsaturated fats.

After 828,000 man years of study the results were as follows: 1015 coronary heart disease deaths in the intervention groups, 1049 in the control groups; 2909 total deaths in the intervention groups, 2947 deaths in the control groups, a difference of 36: that is, four less deaths in 10,000 men per year. Such a small difference is well within the limits of chance.

Particularly in America, the main interest now centres on cholesterol and everybody is being encouraged to know not only their blood pressure but also their cholesterol count. There have been three major trials of reducing cholesterol by drugs in middle aged men whose cholesterol was in the upper ranges of normal. The results after 115,176 man years of observation were as follows: 92 coronary heart deaths in the intervention groups, 100 deaths in the control groups, 275 total deaths in the intervention groups but only 240 deaths in the control groups. In other words, lowering cholesterol with drugs did no good and may have done harm.

The other main risk marker is raised blood pressure. Hypertension, as it is known in medicalese, is perhaps the most widespread and damaging of present day non diseases. The only workable definition of hypertension is "blood pressure that I (the doctor) treat". A study of the prevalence of hypertension in those aged 50-64 in Australia and the US concluded that almost 70 per cent of Australians and almost 50 per cent of Americans were hypertensive. (Hypertension was defined as a systolic pressure of greater than 140 mm Hg and/or a diastolic pressure of 90 mm Hg or more. Systolic is the arterial pressure when the heart pumps blood, diastolic when the heart is resting. We still measure blood pressure in millimeters of mercury since doctors used to measure it with a glass column filled with mercury. )

There is good evidence that treating the small minority of people who have sustained blood pressure of more than 105 mm Hg diastolic reduces the subsequent incidence of stroke.

For anyone else, the results of the Medical Research Council Trial (British Medical Journal, 13 July1985) of treating patients with mild to moderate hypertension with either propranolol or bendrofluazide (a drug which increases the excretion of water and salt) against placebo showed no benefit in reduction of all causes of mortality in those who had received active treatment. In the study 117,534 cases underwent 85,572 patient years of observation. Deaths in the treated group were 248, and in the placebo group 253. Side effects among those receiving bendrofluazide and propranolol included gout, diabetes and impotence.

Those who took placebo tablets did not escape side effects. By 12 weeks, 16 per cent of those men taking the diuretic, 14 per cent of those taking propranolol and 9 per cent of those taking the placebo had become impotent; at two years these figures had risen to 23 per cent in the diuretic group and to 10 per cent in those taking the placebo! This suggests that attaching the label hypertensive has, of itself, deleterious effects.