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Two studies fail to show benefit of aspirin for primary prevention of cardiovascular events in patients with diabetes

Wednesday, November 12 2008 | Comments

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What's This? Results from 2 new studies do not support the use of aspirin for the primary prevention of cardiovascular events in people with diabetes.

In the first trial, which was conducted in Japan, low-dose aspirin did not seem to prevent cardiovascular events in people with type 2 diabetes, although researchers noted a possible benefit in the older participants.

The prospective, randomized, open-label study enrolled 2,539 individuals aged 30 to 85 years who had type 2 diabetes and no history of atherosclerotic disease, including cardiovascular disease, stroke, and peripheral vascular disease. They were randomized to receive 81 mg or 100 mg of aspirin daily (n=1,262) in addition to their current therapy (aspirin group), or to continue current therapy (n=1,277; no-aspirin group). They had follow-up visits every 2 or 4 weeks for a median of 4.37 years.

During follow-up, there were 154 atherosclerotic events, including 68 in the aspirin group (5.4%) and 86 in the no-aspirin group (6.7%), with no significant between-group difference (hazard ratio [HR], 0.80; 95% CI, 0.58-1.10; P=.16).

A combined endpoint of fatal coronary events and fatal cerebrovascular events was the only secondary endpoint that was reduced significantly for the aspirin group. One participant in the aspirin group and 10 in the no-aspirin group had a fatal cerebrovascular event or coronary event (1 stroke in the aspirin group; 5 strokes and 5 myocardial infarctions [MI] in the no-aspirin group [HR 0.10; 95% CI, 0.01-0.79; P=.0037]).

A subgroup analysis of 1,363 participants aged 65 years or older (719 in the aspirin group and 644 in the no-aspirin group) showed the incidence of atherosclerotic events was significantly lower in the aspirin group (45 events, 6.3%) than it was in the no-aspirin group (59 events, 9.2%; HR, 0.68; 95% CI, 0.46-0.99; P=.047). The corresponding difference among participants aged younger than 65 years was not significant (P=.98).

The researchers found a "small increase" in cases of serious gastrointestinal bleeding among the participants using aspirin, with 4 aspirin-treated patients requiring transfusions, but there was no excess of fatal gastrointestinal or cerebral hemorrhages.

The investigators noted that interpretation of their results is "challenging" because the overall event rates were only one-third of those anticipated in their sample-size calculations.

The study was published online Nov. 9 ahead of print in JAMA by Ogawa H, et al.

"[M]uch longer follow-up, or a larger sample, would have been needed to reliably estimate benefits and risks related to aspirin therapy," concluded Dr. Antonio Nicolucci, a member of the department of clinical pharmacology and epidemiology at Consorzio Mario Negri Sud in Italy, in an accompanying editorial.

In related news, a smaller, randomized controlled trial conducted in Scotland recently looked at whether aspirin, alone or combined with antioxidant therapy, was more effective than placebo in reducing the development of cardiovascular events in people with type 1 or type 2 diabetes and asymptomatic peripheral arterial disease (n=1,276).

This study produced no evidence to support the use of either aspirin or antioxidants in the primary prevention of cardiovascular events and mortality in individuals with diabetes. Overall, 116 primary events (death from coronary heart disease [CHD] or stroke, nonfatal MI or stroke, or amputation above the ankle for critical limb ischemia) occurred in the aspirin groups compared with 117 events in the no-aspirin groups (18.2% vs 18.3%, respectively; HR, 0.98; 95% CI, 0.76-1.26). There was also no significant difference between the aspirin and no-aspirin groups in the second composite primary endpoint: death from CHD or stroke (HR, 1.23; 95% CI, 0.79-1.93). (Belch J, et al. BMJ 2008;337:1840.)

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