Aspirin for primary prevention of CVD: Are the right people using it?

ABSTRACT

Purpose
Aspirin is recommended for the primary prevention of cardiovascular disease (CVD) in adults at high risk, but little is known about sociodemographic disparities in prophylactic aspirin use. This study examined the association between sociodemographic characteristics and regular aspirin use among adults in Wisconsin who are free of CVD.

Methods
A cross-sectional design was used, and data collected from 2008 to 2010. Regular aspirin use (aspirin therapy) was defined as taking aspirin most days of the week. We found 831 individuals for whom complete data were available for regression analyses and stratified the sample into 2 groups: those for whom aspirin therapy was indicated and those for whom it was not indicated, based on national guidelines.

Results
Of the 268 patients for whom aspirin therapy was indicated, only 83 (31%) were using it regularly, and 102 (18%) of the 563 participants who did not have an aspirin indication were taking it regularly. In the group with an aspirin indication, participants who were older had higher rates of regular aspirin use than younger patients (odds ratio [OR]=1.07; P<.001), and women had significantly higher adjusted odds of regular aspirin use than men (OR=3.49; P=.021). Among those for whom aspirin therapy was not indicated, the adjusted odds of regular aspirin use were significantly higher among older participants (OR=1.07; P<.001) vs their younger counterparts, and significantly lower among Hispanic or nonwhite participants (OR=0.32; P=.063) relative to non-Hispanic whites.

Conclusions
Aspirin therapy is underused by those at high risk for CVD—individuals who could gain cardioprotection from regular use—and overused by those at low risk for CVD, for whom the risk of major bleeding outweighs the potential benefit. Stronger primary care initiatives may be needed to ensure that patients undergo regular screening for aspirin use, particularly middle-aged men at high CVD risk. Patient education may be needed, as well, to better inform people (particularly older, non-Hispanic whites) about the risks of regular aspirin use that is not medically indicated.

Cardiovascular disease (CVD) is the principal cause of death in the United States.¹ As the population grows older and obesity and diabetes become increasingly prevalent, the prevalence of CVD is also expected to rise.^2,3 Fortunately, many CVD events can be prevented or delayed by modifying risk factors such as hyperlipidemia, hypertension, and smoking. Interventions associated with a reduction in risk have led to a reduction in CVD events^4,5 and contributed to a steady decline in cardiac deaths.⁶

Control of platelet aggregation is a cornerstone of primary CVD prevention.⁷ In an outpatient setting, this usually translates into identifying patients who are at high risk for a CVD event and advising them to take low-dose aspirin daily or every other day. Although not without controversy,^8,9 the US Preventive Services Task Force (USPSTF) recommends regular aspirin use for primary CVD prevention for middle-aged to older men at high risk for myocardial infarction (MI) and women at high risk for ischemic stroke.¹⁰

The efficacy of this intervention is proven: In primary prevention trials, regular aspirin use is associated with a 14% reduction in the likelihood of CVD events over 7 years.¹¹ What’s more, aspirin therapy, as recommended by the USPSTF, is among the most cost-effective clinic-based preventive measures.¹²

In 2004, 41% of US adults age 40 or older reported taking aspirin regularly¹³—an increase of approximately 20% since 1999.¹⁴ More recent data from a national population-based cohort study found that 41% of adults ages 45 to 90 years who did not have CVD but were at moderate to high risk for a CVD event reported taking aspirin ≥3 days per week.¹⁵ In the same study, almost one-fourth of those at low CVD risk also reported regular aspirin use.

While regular aspirin use for primary CVD prevention has been on the rise,^13,14 the extent to which this intervention has penetrated various segments of the population is unclear. Several studies have found that aspirin use is consistently highest among those who are older, male, and white.^15-17 Other socioeconomic variables (eg, education level, employment, marital status) have received little attention. And no previous study has used national guidelines for aspirin therapy to stratify samples.

A look at overuse and underuse. To ensure that aspirin therapy for primary CVD prevention is directed at those who are most likely to benefit from it, a better understanding of variables associated with both aspirin overuse and underuse is needed. This area of research is important, in part because direct-to-consumer aspirin marketing may be particularly influential among groups at low risk for CVD—for whom the risk of excess bleeding outweighs the potential for disease prevention.^13,18