IMPORTANCE The American College of Cardiology and the American Heart Association (ACC/AHA) cholesterol treatment guidelines have wide-scale implications for treating adults without history of atherosclerotic cardiovascular disease (ASCVD) with statins.   
 OBJECTIVE To estimate the cost-effectiveness of various 10-year ASCVD risk thresholds that could be used in the ACC/AHA cholesterol treatment guidelines.   
 DESIGN, SETTING, AND PARTICIPANTS Microsimulation model, including lifetime time horizon, US societal perspective, 3% discount rate for costs, and health outcomes. In the model, hypothetical individuals from a representative US population aged 40 to 75 years received statin treatment, experienced ASCVD events, and died from ASCVD-related or non-ASCVD-related causes based on ASCVD natural history and statin treatment parameters. Data sources for model parameters included National Health and Nutrition Examination Surveys, large clinical trials and meta-analyses for statin benefits and treatment, and other published sources.   
 MAIN OUTCOMES AND MEASURES Estimated ASCVD events prevented and incremental costs per quality-adjusted life-year (QALY) gained.   
 RESULTS In the base-case scenario, the current ASCVD threshold of 7.5% or higher, which was estimated to be associated with 48% of adults treated with statins, had an incremental cost-effectiveness ratio (ICER) of $37,000/QALY compared with a 10% or higher threshold. More lenient ASCVD thresholds of 4.0% or higher (61% of adults treated) and 3.0% or higher (67% of adults treated) had ICERs of $81,000/QALY and $140,000/QALY, respectively. Shifting from a 7.5% or higher ASCVD risk threshold to a 3.0% or higher ASCVD risk threshold was estimated to be associated with an additional 161,560 cardiovascular disease events averted. Cost-effectiveness results were sensitive to changes in the disutility associated with taking a pill daily, statin price, and the risk of statin-induced diabetes. In probabilistic sensitivity analysis, there was a higher than 93% chance that the optimal ASCVD threshold was 5.0% or lower using a cost-effectiveness threshold of $100,000/QALY.   
 CONCLUSIONS AND RELEVANCE In this microsimulation model of US adults aged 45 to 75 years [corrected], the current 10-year ASCVD risk threshold (≥7.5% risk threshold) used in the ACC/AHA cholesterol treatment guidelines has an acceptable cost-effectiveness profile (ICER, $37,000/QALY), but more lenient ASCVD thresholds would be optimal using cost-effectiveness thresholds of $100,000/QALY (≥4.0% risk threshold) or $150,000/QALY (≥3.0% risk threshold). The optimal ASCVD threshold was sensitive to patient preferences for taking a pill daily, changes to statin price, and the risk of statin-induced diabetes.
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