Low dose aspirin is a recommended treatment for patients with a history of heart disease to help prevent blood clots forming. However, discontinuation rates of up to 50% have been reported in long-term users.
Studies in hospitals have shown that stopping low dose aspirin is linked with an increased risk of heart problems, but there have been no studies looking at the impact of stopping low dose aspirin on the risk of heart attack or death from coronary heart disease in the general population.
So Dr Luis Garcia Rodriguez and colleagues analysed data on 39,513 patients from The Health Improvement Network, a large database of UK primary care records.
Patients were aged 50 to 84 years with a first low dose acetylsalicylic acid (aspirin) prescription for prevention of cardiovascular outcomes from 2000 to 2007.
Patients were followed up for just over three years to compare cases of non-fatal heart attacks and deaths from coronary heart disease in subjects who had discontinued treatment with those who had continued therapy.
Compared with current users, recent discontinuers of low dose aspirin were at a significantly increased risk (60%) of non-fatal heart attack, irrespective of the length of time the patient had been taking low dose aspirin. This means that, for every 1,000 patients over a one-year period, there were around four extra cases of non-fatal heart attack among patients who recently discontinued low dose aspirin compared with those who continued therapy.
Recent discontinuers of low dose aspirin were also at a significantly increased risk of non-fatal heart attack or death from coronary heart disease combined, but there was no increase in risk of coronary heart disease death alone in patients who discontinued treatment.
These findings suggest that reducing the number of patients who discontinue low dose aspirin could have a major impact on the benefit obtained with low dose aspirin in the general population, say the authors.
They call for further research to test whether efforts to encourage patients to continue prophylactic treatment with low dose aspirin will result in a decrease in non-fatal heart attacks.
"These findings are important and support previous studies showing an increase in adverse events after aspirin withdrawal," say experts from Italy in an accompanying editorial.
Results of further studies are eagerly awaited, they say. In the meantime, patients should be advised never to stop aspirin unless explicitly told to do so, and doctors should maintain their patients on low dose aspirin for as long as they can.
