The benefits of reducing cholesterol levels - the need to distinguish primary from secondary prevention 2. Implications for heart disease prevention in Australia

Objective: To estimate the number of coronary heart disease (CHD) events arising from the primary and secondary prevention populations of middle-aged Australian men and the potential impact in each setting of lipid-lowering therapy on death from CHD. Design: Analysis based on results of a meta-analysis of drug trials to lower cholesterol levels and data from the Hunter Region Heart Disease Prevention Programme. Main outcome measure: Death from CHD. Results: Over a five year period, 1520 fatal CHD events would be expected in a population of 100 000 men aged 35 to 69 years. Approximately 52% would arise from subjects already known to suffer from CHD. We predict that treating everyone in the secondary prevention group who has a blood cholesterol level of >5.2mmol/L (approximately 5000 subjects) would prevent 118 deaths, compared with 51 deaths prevented by treating those in the primary prevention group who have cholesterol levels of >6.2mmol/L (approximately 30 000 subjects). The outcome is maintained in several sensitivity analyses. Conclusions: The majority of persons in whom death from CHD might be prevented by treatment to lower cholesterol levels can be identified by targeting subjects for secondary prevention. Therapy in the secondary prevention setting is much more efficient than in primary prevention.