Underutilization of Aspirin Persists in US Ambulatory Care for the Secondary and Primary Prevention of Cardiovascular Disease

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These risk estimates should be evaluated in the context of average reductions of 15-40% in cardiovascular events when aspirin is used as a preventive therapy.3,10,11,14,35 Accurate risk assessment can be difficult at the individual patient level, especially when discrepancies arise between verbal and written medical history information.36 Aspirin resistance may also limit the rates of aspirin use. However, the frequency of aspirin resistance is less well known and may range from 5 to 60%.37 In some patients it may be dose related. Lee et al.38 indicate that even low-dose aspirinÔÇö100mg or lessÔÇömay increase aspirin resistance in patients with coronary artery disease.

Past research also suggests that physicians may assign lower priority to aspirin therapy than to other cardiovascular risk-lowering therapies,25,26,36 and our evaluations of the co-prescription of aspirin and statins support this assessment. We found that aspirin and statin use was significantly higher when the other therapy was present; however, the incremental use became progressively greater for statins over time. Beginning in 1997-1998, statin use in the presence of aspirin transcended aspirin use in the presence of statins for both the high- and intermediate-risk categories, and the gaps remained wide through 2003. These results suggest that even though statins themselves may be underused, aspirin is given even lower priority for lowering cardiovascular risk. These findings are intriguing because both therapies reduce cardiovascular risk by similar magnitudes but differ vastly in cost; statins are prioritized despite the far greater cost-effectiveness of aspirin.39-41 Also, secondary analyses of clinical trial data indicate that aspirin and statins used in combination may be more effective at reducing the relative risk of CVD events than when used alone.42

Statins are newer and more intensely advertised than aspirin, which may partly explain the preferential use of these drugs. Lipid-lowering medications already ranked as the fifth most promoted drug class in the US in 1998.43 Statins are proven effective for both the primary and secondary prevention of CVD, whereas the effectiveness of aspirin in primary prevention is less certain. Also, while they are increasingly used as a prophylactic treatment, statins are still most commonly prescribed to people with hyperlipidemia. In contrast, use of aspirin is not specific to any risk factor in the prevention of CVD and therefore may be neglected by many physicians who are trained to perform in an overly acute-care-centered healthcare system.

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