West of Scotland Coronary Prevention Study: identification of high-risk groups and comparison with other cardiovascular intervention trials.

BACKGROUND

We assessed the potential benefit of treatment for low-risk and high-risk groups in the West of Scotland Coronary Prevention Study (WOSCOPS) population, and compared the benefits of primary and secondary prevention of coronary heart disease (CHD) by lipid lowering with the benefits of blood pressure reduction in the primary prevention of stroke.

METHODS

We did a subgroup analysis of placebo-treated men in the WOSCOPS population by age, vascular disease at trial entry, and other established risk factors. We also compared WOSCOPS findings with those of the Scandinavian Simvastatin Survival Study (4S) and the Medical Research Council (MRC) trial of treatment for mild to moderate hypertension in middle-aged men. The WOSCOPS population comprised 6595 men aged 45-64 years with no history of myocardial infarction (MI) and plasma total cholesterol concentrations of 6.5-8.0 mmol/L at initial screening. Participants were randomly allocated pravastatin (40 mg daily) or placebo, and followed up for an average of 4.9 years.

FINDINGS

Coronary event rates at 5 years in the WOSCOPS placebo group were higher than 10% (the recommended treatment threshold) in men with pre-existing vascular disease and in those 55 years or older without symptoms or signs of CHD but with at least one other risk factor. Event rates were low in men with hypercholesterolaemia but no other risk factor: 3.5% (95% CI 1.3-5.7) for men aged 45-54 years and 5.3% (2.7-8.0) for men aged 55-64 years. Three times more men had to be treated for 5 years to prevent one endpoint in WOSCOPS than in 4S. By contrast, two to four times fewer men with hyperlipidaemia were treated to save one coronary event in WOSCOPS than hypertensives to save one stroke in the MRC trial. These differences persisted after adjustment for the low-risk status of many of the patients with hypertension who took part in the MRC trial.

INTERPRETATION

There were a substantial number of men whose risk of a coronary event was more than 10% at 5 years in the WOSCOPS cohort. The absolute benefit of pravastatin treatment of hyperlipidaemia is less in the primary prevention of CHD than in secondary prevention, but is similar to that for primary prevention of stroke by treatment of mild to moderate hypertension in middle-aged men.