Serum cholesterol and ischaemic heart disease.

A systematic examination of the evidence on the relationship between serum cholesterol and ischaemic heart disease shows conclusively that serum cholesterol reduction in populations with high rates of heart disease is an effective and safe method of reducing ischaemic heart disease rates. The relative protective effect is greater at younger ages (50% reduction at age 40 for a 0.6 mmol/l reduction in serum cholesterol declining to about 20% at age 70 or more). The absolute protective effect is greater if the disease is common because the effect of a give serum cholesterol reduction is proportional to the prevailing heart disease rate. The full effect of a serum cholesterol reduction is evident after about 5 years. The use of drugs of the 'statin' type can lower serum cholesterol by about 1.8 mmol/l, yielding a reduction in risk of about 60% at age 60. A diet typical in Japan would lower serum cholesterol by about 1.2 mmol/l and lead to a halving of the risk. Only modest serum cholesterol reductions (about 0.3 mmol/l) are generally achievable by individuals altering their diet independently of others and this is expected to lead to a 15% reduction in the risk of ischaemic heart disease at age 60. Larger reductions (about 0.6 mmol/l) require collective action over the supply and preparation of food which could reduce the risk by about 30%. Achieving the full impact of serum cholesterol reduction in a population will require a national nutritional policy. It is not something that can be effectively left to individual action.