Despite a lot of good press for aspirin with regards to prevention of cardiovascular events and cancer prevention, determining who should take aspirin is quite tricky.  This blog entry will discuss the vascular rationale and a subsequent post will tackle the potential of aspirin for colorectal cancer prevention.

At this time, the cardiovascular disease (CVD) rationale includes preventing myocardial infarction [MI] and stroke.  These are the main determinants of risk/benefit for taking aspirin.  In 2009, guidelines from US Preventive Services Task Force (USPSTF) for taking aspirin were published (Ann Intern Med 2009; 150: 396-404).  The following link can be used to access this article:

http://www.uspreventiveservicestaskforce.org/uspstf09/aspirincvd/aspcvdrs.pdf

The recommendations include the following:

Men <45:  Not encourage aspirin for MI prevention

Women <55: Not encourage aspirin for stroke prevention

Men 45-79:  Encourage aspirin when CVD benefit.  Benefit likely if:

• 45-59 years, 10 -year CVD risk ≥4%
• 60-69 years, 10-year CVD risk ≥9%
• 70-79 years, 10-year CVD risk ≥12%

Women 55-79:  Encourage aspirin when stroke benefit.  Benefit likely if:

• 55-59 years, 10 -year stroke risk ≥3%
• 60-69 years, 10 -year stroke risk ≥8%
• 70-59 years, 10 -year stroke risk ≥11%

To calculate 10 -year stroke risk: http://my.clevelandclinic.org/p2/stroke-risk-calculator.aspx

Risk factors: age, high blood pressure, diabetes, smoking, history of CVD, atrial fibrillation, and left ventricular hypertrophy

In addition, it is noted that aspirin is NOT recommended when other NSAIDs are being administered or if history of GI ulcers/risk of serious GI bleeding.

While these recommendations are a useful starting point and the risk calculators are fascinating, the absolute benefit of aspirin remains unclear.  A recent article on this subject indicates that aspirin may not improve mortality (Arch Intern Med. 2012;172(3):209-216. doi:10.1001/archinternmed.2011.628).  This article reviewed nine large randomized placebo-controlled studies, each with at least 1000 participants.  In total, more than 100,000 patients were described in these studies.  While CVD events were reduced by 10%, there was no reduction in mortality for cardiovascular disease (OR 0.99) or for cancer (OR 0.93) among aspirin takers over a mean of 6 years.  Most of the reduction in CVD events were due to a lower rate of non-fatal MI (OR 0.80).  In addition, there was an increase in significant GI bleeding among patients taking aspirin (OR 1.31)

Due to these results, the authors conclude that routine use as primary prevention is not warranted; “treatment decisions need to be considered on a case-by-case basis.”

Additional reference:

• –Arch Intern Med 2012;172:217-218.  Aspirin Therapy in Primary Prevention: Comment on “Effect of Aspirin on Vascular and Nonvascular Outcomes”