Narrative Review: Lack of Evidence for Recommended Low-density Lipoprotein Treatment Targets: a Solvable Problem

Recent national recommendations have proposed that physicians should titrate lipid therapy to achieve low-density lipoprotein (LDL) cholesterol levels less than 1.81 mmol/L (<70 mg/dL) for patients at very high cardiovascular risk and less than 2.59 mmol/L (<100 mg/dL) for patients at high cardiovascular risk. To examine the clinical evidence for these recommendations, the authors sought to review all controlled trials, cohort studies, and case-control studies that examined the independent relationship between LDL cholesterol and major cardiovascular outcomes in patients with LDL cholesterol levels less than 3.36 mmol/L (<130 mg/dL). For those with LDL cholesterol levels less than 3.36 mmol/L (<130 mg/dL), the authors found no clinical trial subgroup analyses or valid cohort or case-control analyses suggesting that the degree to which LDL cholesterol responds to a statin independently predicts the degree of cardiovascular risk reduction. Published studies had avoidable limitations, such as a reliance on ecological (aggregate) analyses, use of analyses that ignore statins' other proposed mechanisms of action, and failure to account for known confounders (especially healthy volunteer effects). Clear, compelling evidence supports near-universal empirical statin therapy in patients at high cardiovascular risk (regardless of their natural LDL cholesterol values), but current clinical evidence does not demonstrate that titrating lipid therapy to achieve proposed low LDL cholesterol levels is beneficial or safe.