Clinical Trials: Evidence and Unanswered Questions – Hyperlipidaemia

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Abstract
It is now clear that the management of hypercholesterolaemia is important for the reduction of morbidity and mortality caused by cerebrovascular and coronary events. The landmark Scandinavian Simvastatin Survival Study was the first to show conclusively that lipid-lowering therapy with statins reduces the incidence of stroke. Subsequent trials, undertaken in a variety of different patient populations, have confirmed that statin therapy reduces the incidence of stroke by approximately one-third. This important benefit has been observed in men and women, the young and the elderly, and also in subjects with diabetes mellitus. In the recent Heart Protection Study, which recruited ‘high-risk’ vascular subjects, stroke risk reduction was demonstrated even among those subjects considered to have ‘low’ low-density lipoprotein (LDL) cholesterol levels. The benefits of statin therapy in stroke have been attributed to reductions in cholesterol and to other non-lipid-lowering effects of statins. Ongoing clinical trials such as TNT (Treating to New Targets) and IDEAL (Incremental Decrease in Endpoints through Aggressive Lipid lowering) will test the ‘lower is better’ hypothesis. Using statins to lower LDL cholesterol to levels that are below current guidelines will provide additional benefits in stroke risk reduction. Most of the data on cholesterol reduction and cerebrovascular events have been derived from studies of patients with documented coronary heart disease (CHD). The ongoing SPARCL (Stroke Prevention by Aggressive Reduction in Cholesterol Levels) trial will examine the benefits of LDL cholesterol lowering in patients with previous stroke or transient ischaemic attack (TIA), but no history of coronary problems.