Statins are HMG-CoA reductase inhibitors that work by blocking an enzyme in the liver responsible for cholesterol production. This mechanism effectively lowers the concentration of low-density lipoprotein (LDL) cholesterol in the bloodstream. The primary objective of this therapy is to reduce the risk of serious cardiovascular events, such as heart attack and stroke, by preventing the buildup of atherosclerotic plaque in the arteries. Deciding when to initiate statin therapy requires an individualized assessment of a person’s total cardiovascular risk, moving beyond simple cholesterol numbers.
Initial Steps: Prioritizing Lifestyle and Calculating Risk
Before medication is considered, the first course of action involves maximizing lifestyle interventions aimed at improving cardiovascular health. These interventions include adopting a heart-healthy diet, engaging in regular physical activity, maintaining a healthy body weight, and achieving smoking cessation. In many cases, these changes alone can significantly improve cholesterol profiles and reduce overall risk.
The decision to add a statin is primarily guided by calculating the 10-year Atherosclerotic Cardiovascular Disease (ASCVD) Risk Score. This standardized tool estimates the percentage likelihood of experiencing a heart attack or stroke in the next decade. The calculation uses several patient-specific factors, including age, sex, race, cholesterol levels (total and HDL), systolic blood pressure, diabetes status, and smoking status. The resulting percentage score serves as the foundation for the discussion between the patient and physician regarding treatment.
Criteria for Primary Prevention: Starting Statins Based on Risk Score
Primary prevention focuses on preventing a person’s first cardiovascular event. For adults aged 40 to 75 years who do not have established ASCVD, statin therapy is recommended based on their calculated risk and LDL cholesterol level.
For individuals with an ASCVD risk score of 7.5% to 20% (intermediate risk), the decision to start a statin is often a shared discussion. This conversation may involve assessing additional risk-enhancing factors, such as a family history of premature heart disease, persistently elevated LDL cholesterol (above 160 mg/dL), or chronic inflammatory conditions. A Coronary Artery Calcium (CAC) score can also refine the risk estimate; a score of zero may suggest withholding therapy, while a score of 100 or greater favors starting treatment.
Statins are recommended for individuals whose 10-year ASCVD risk is 20% or higher (high-risk category). Therapy is also recommended for those with very high baseline LDL cholesterol levels, specifically 190 mg/dL or greater, regardless of their calculated ASCVD risk score. The goal for these high-risk groups is to achieve a substantial reduction in LDL cholesterol, typically 50% or more, requiring a high-intensity statin regimen.
Criteria for Secondary Prevention: Starting Statins After a Cardiovascular Event
Secondary prevention aims to prevent a subsequent cardiovascular event in someone who has already experienced one. Individuals with a history of myocardial infarction, ischemic stroke, transient ischemic attack (TIA), stable or unstable angina, or peripheral artery disease (PAD) fall into this category. Because the patient is automatically classified as being at very high risk, the criteria for starting statin therapy are strict.
For these patients, high-intensity statin therapy is initiated as soon as possible after the event, regardless of their baseline LDL cholesterol measurement. The goal is to lower LDL cholesterol to below 70 mg/dL, and often below 55 mg/dL for those at the highest risk. The prior event confirms the presence of significant atherosclerotic disease.
Special Populations: Adjusting Guidelines for Specific Health Conditions
The standard ASCVD risk calculation is sometimes bypassed or modified for specific patient populations whose inherent risk is already elevated. For all patients with Type 1 or Type 2 Diabetes between 40 and 75 years old, statin therapy is routinely recommended for primary prevention. A moderate-intensity statin is the minimum recommendation, moving to high-intensity therapy if multiple other risk factors are present.
Individuals diagnosed with Familial Hypercholesterolemia (FH) represent another group where standard guidelines do not apply. This genetic condition results in extremely high LDL cholesterol levels (often 190 mg/dL or greater), causing premature heart disease. Treatment often begins in childhood or young adulthood to combat lifelong exposure to high cholesterol, requiring maximally tolerated high-intensity statin therapy, sometimes combined with other lipid-lowering agents.
For adults over the age of 75, the decision to start a statin for primary prevention is more nuanced. Standard risk calculators may overstate the benefit because age is a dominant factor in the score. The focus shifts to discussing potential benefits versus risks, such as frailty and polypharmacy. While moderate-intensity statin therapy may be considered for those in good health, the decision is highly individualized, relying on clinical judgment rather than strict adherence to a percentage-based risk score.