Low-Dose Aspirin Reduces Heart Disease But Not Diabetes

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A randomized trial of low-dose aspirin in the prevention of clinical type 2 diabetes in women, by Aruna D. Pradhan and colleagues. Diabetes Care 32:3–8, 2009

What is the problem and what is known about it so far?

More than 125 years ago, aspirin was reported to reduce blood glucose levels. However, this effect was not explored more fully until recently, when type 2 diabetes was linked to inflammation, the body's basic response to injury and infection. This may be a particularly important link for women, who may be more likely to have inflammation caused by obesity.  Aspirin reduces inflammation. Several small studies have shown that taking high doses of aspirin over a short time period can reduce insulin resistance (problems using insulin from the pancreas to properly process blood glucose), which often leads to type 2 diabetes. But high doses of aspirin can cause side effects, including bleeding and stomach problems. It is not known whether taking low doses of aspirin over a long period of time might also reduce insulin resistance and help to prevent diabetes.

Why did the researchers do this particular study?

The researchers wanted to find out whether long-term, low-dose aspirin therapy can prevent the development of type 2 diabetes in women.

Who was studied?

The study included more than 38,500 initially healthy women who were enrolled in a 10-year study of aspirin and vitamin E to prevent heart disease and cancer.

How was the study done?

The researchers examined records about how many women developed type 2 diabetes during the course of the heart disease and cancer trial. They also took into account the presence of various known diabetes risk factors, such as age, body mass index (a measure of overweight), family history, degree of physical activity, A1C levels, and other factors.

What did the researchers find?

There was no difference between women who took aspirin and those who did not in the number of new cases of type 2 diabetes. This held true even after taking into account patients' diabetes risk factors, lengths of time on aspirin therapy, and success in sticking to their aspirin regimen.

What were the limitations of the study?

It is possible that the dose of aspirin used in this study (100 mg every other day) was not high enough to have an effect and that some intermediate dose may be more helpful. Also, women enrolled in the heart disease and cancer trial had a relatively low risk of developing diabetes compared to the general population. Aspirin therapy in higher-risk women may yield different results. The heart disease and cancer study may have under-diagnosed diabetes in its participants. Women were not all screened for diabetes or its underlying markers.

What are the implications of the study?

This study suggests that long-term low-dose aspirin does not prevent the development of type 2 diabetes among initially healthy women. Additional research is needed on the potential benefit of higher aspirin doses for women with higher risks. But any benefits found must be weighed against the serious side effects that aspirin can cause.

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