David Brill
Aspirin should not be used routinely for primary prevention of cardiovascular disease in people with asymptomatic atherosclerosis, results of a randomized trial suggest.
The Aspirin for Asymptomatic Atherosclerosis (AAA) study found that daily aspirin (100mg) did not significantly reduce vascular events compared to placebo, but increased rates of hemorrhage and gastrointestinal complications.
The trial involved 3,350 Scottish men and women aged 50 to 75 who had a low ankle brachial index (ABI; ≤ 0.95) – indicative of peripheral atherosclerosis. They were followed up for a mean of 8.2 years for primary outcomes of coronary events, stroke and revascularization.
A total of 357 study subjects experienced a vascular event: 181 in the aspirin group and 176 in the placebo group (hazard ratio 1.03, 95% CI 0.84 – 1.27). Secondary outcomes, including angina, transient ischemic attack and all-cause mortality, were also not significantly different between groups.
“There is no support for the routine use of aspirin for the prevention of vascular events in the context of ABI screening in the general population,” said study investigator Professor Gerald Fowkes of the University of Edinburgh, UK.
“It is possible that in the general population, aspirin could produce a smaller reduction in vascular events than this trial was powered to detect, but it is questionable whether such an effect, together with aspirin related morbidity, would justify the additional resources and health care requirements of an ABI screening program,” he said.
Fowkes noted that compliance is lower in the primary prevention setting, adding: “Whether aspirin is beneficial in clinical practice in a patient with a low ABI who was fully compliant with the medication is unknown, so our results cannot be extrapolated into that situation.”
Thirty four major hemorrhages occurred in the aspirin group and 20 in the placebo group (2 percent versus 1.2 percent; hazard ratio 1.71; 95% CI 0.99 – 2.97). There were 14 and eight cases, respectively, of gastrointestinal ulcers (0.8 versus 0.5 percent).
The efficacy of aspirin is well established for secondary prevention in patients with a history of cardiovascular disease, but the risk-benefit ratio for primary prevention in low-risk individuals remains less clear. A recent meta-analysis of six primary prevention trials found that aspirin reduced rates of serious vascular events by 12 percent, but increased major gastrointestinal and extracranial bleeds. [Lancet 2009;373:1849-60]
Recent studies have also questioned the use of aspirin for primary prevention in diabetic patients – a common practice which is advocated in international guidelines. [BMJ 2008;337:a1840]
The trial involved 3,350 Scottish men and women aged 50 to 75 who had a low ankle brachial index (ABI; ≤ 0.95) – indicative of peripheral atherosclerosis. They were followed up for a mean of 8.2 years for primary outcomes of coronary events, stroke and revascularization.
A total of 357 study subjects experienced a vascular event: 181 in the aspirin group and 176 in the placebo group (hazard ratio 1.03, 95% CI 0.84 – 1.27). Secondary outcomes, including angina, transient ischemic attack and all-cause mortality, were also not significantly different between groups.
“There is no support for the routine use of aspirin for the prevention of vascular events in the context of ABI screening in the general population,” said study investigator Professor Gerald Fowkes of the University of Edinburgh, UK.
“It is possible that in the general population, aspirin could produce a smaller reduction in vascular events than this trial was powered to detect, but it is questionable whether such an effect, together with aspirin related morbidity, would justify the additional resources and health care requirements of an ABI screening program,” he said.
Fowkes noted that compliance is lower in the primary prevention setting, adding: “Whether aspirin is beneficial in clinical practice in a patient with a low ABI who was fully compliant with the medication is unknown, so our results cannot be extrapolated into that situation.”
Thirty four major hemorrhages occurred in the aspirin group and 20 in the placebo group (2 percent versus 1.2 percent; hazard ratio 1.71; 95% CI 0.99 – 2.97). There were 14 and eight cases, respectively, of gastrointestinal ulcers (0.8 versus 0.5 percent).
The efficacy of aspirin is well established for secondary prevention in patients with a history of cardiovascular disease, but the risk-benefit ratio for primary prevention in low-risk individuals remains less clear. A recent meta-analysis of six primary prevention trials found that aspirin reduced rates of serious vascular events by 12 percent, but increased major gastrointestinal and extracranial bleeds. [Lancet 2009;373:1849-60]
Recent studies have also questioned the use of aspirin for primary prevention in diabetic patients – a common practice which is advocated in international guidelines. [BMJ 2008;337:a1840]
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