Aspirin and diabetes and primary prevention

by Dr. Bill Quick
Sunday, October 19, 2008

For many years, it's been a standard recommendation that PWD take aspirin to help protect against heart attacks and strokes, both if they've already had such an event (in which case, it's called "secondary prevention"), or even if they have never had either a heart attack or stroke (which is called "primary prevention"). The recommendation for use of aspirin in primary prevention is now being questioned.

According to an article recently published in the British Medical Journal, researchers found no evidence of benefit from either aspirin or antioxidant treatment given for about 7 years to adults with diabetes who were given it for primary prevention of heart attack and stroke. They state "This trial does not provide evidence to support the use of aspirin or antioxidants in primary prevention of cardiovascular events and mortality in the population with diabetes studied." The authors point out that aspirin should still be given for secondary prevention of cardiovascular disease in people with diabetes mellitus, when the evidence is convincing.

The researchers studied 1276 Scottish adults aged 40 or more with type 1 or type 2 diabetes, who had no symptomatic cardiovascular disease. Patients were divided into four groups: 100 mg daily aspirin plus antioxidant capsule (n=320), aspirin tablet plus placebo capsule (n=318), placebo tablet plus antioxidant capsule (n=320), or placebo tablet plus placebo capsule (n=318). The antioxidant capsule contained alpha-tocopherol, ascorbic acid, pyridoxine, zinc, nicotinamide, lecithin, and selenite. The study was double-blinded (that is, neither the researchers nor the patients knew what they were receiving). Participants also were allowed to receive standard therapy as appropriate (for example, statins) at the discretion of their physicians.

Important in analyzing the outcomes of the study is the duration of the trial: if folks were watched for only a few days, it's obvious that no difference would be seen. In reality, the median length of follow-up for randomized participants was 6.7 years and for those with a final follow-up in 2006 follow-up ranged from 4.5 to 8.6 years.

The American Diabetes Association, the American Heart Association and the U.S. government, have all recommended aspirin for people who have not had heart attacks or strokes but are at high risk for cardiovascular trouble because of conditions such as diabetes. The issue, if you do not have heart disease, is whether the risk of gastrointestinal bleeding as a side effect of aspirin outweighs any benefit you get from taking it. For example, the ADA in 2004 stated that aspirin "has been used as a primary and secondary strategy to prevent cardiovascular events in nondiabetic and diabetic individuals. Meta-analyses of these studies and large-scale collaborative trials in men and women with diabetes support the view that low-dose aspirin therapy should be prescribed as a secondary prevention strategy, if no contraindications exist. Substantial evidence suggests that low-dose aspirin therapy should also be used as a primary prevention strategy in men and women with diabetes who are at high risk (over age 40 or with other CVD risk factors) for cardiovascular events. Despite its proven efficacy, aspirin therapy is underutilized in patients with diabetes. Available data suggest that less than half of eligible patients are being treated with aspirin."