Low-Dose Aspirin Used Less, is Less Effective in Black Americans

Rodrigo Fernandez-Jimenez, MD, PhD

New research into the effects and usage of low-dose aspirin found black Americans were less likely to use low-dose aspirin and, among those who did, it appeared to be ineffective for primary prevention or reducing the risk of death.

The 11-year follow-up study, which included more than 65,000 individuals, revealed no evidence low-dose aspirin has a beneficial effect among black American for primary prevention of cardiovascular disease.

"Most available data shows that African Americans have a higher risk of having a heart attack, stroke or other heart diseases compared to whites; however, previous studies didn't include enough black participants to determine if taking a low-dose aspirin for primary prevention of heart disease was useful for this group of people," said Rodrigo Fernandez-Jimenez, MD, PhD, cardiologist and researcher at Centro Nacional de Investigaciones Cardiovasculares (CNIC) in Madrid, Spain.

To further detail the usage rates and effectiveness of low-dose aspirin among black Americans compared to their white counterparts, investigators performed an observational analysis of data from the Southern Community Cohort Study. From the study, a cohort of 65,231 non-Hispanic black and white adults between the age of 40 and 79 years with no history of cardiovascular disease was identified for inclusion.

Upon entry, investigators calculated Framingham 10-year cardiovascular disease risk. Additionally, sociodemographic data, lifestyle characteristics, and medical history were obtained through interviews at community health centers or self-administered mail questionnaire.

Investigators defined low-dose aspirin as baby aspirin, half tablets of aspirin, or low-dose aspirin. Regular use was classified as taking low-dose aspirin 2 or more time per week for a month or longer.

Of the 65,231 patients, the mean age was 51.5 years, 60.1% were female, 70.2% were non-Hispanic black and 29.8% were non-Hispanic white. Investigators noted 44,591 participants were classified as being at a high risk, while 12,409 were considered intermediate risk and the remaining 8231 were considered low risk.

Analyses revealed regular low-dose aspirin use was present in 17.1% of patients and the proportion increased with a patient’s predicted 10 year risk (7.5% low-, 11.6% intermediate-, and 20.4% among high-risk patients; P<0.001). Among regular users, the median number of pills consumed per week was 7.

When compared to their white counterparts, blacks were less likely to take low-dose aspirin—regardless of cardiovascular disease risk and significant covariates (aOR=0.79; 95% CI: 0.75-0.82). During a median follow-up period of 11.3 years, investigators observed low-dose aspirin was associated with decreased risk of ischemic cardiac death in whites (aHR=0.86; 95%CI: 0.68-1.10) but not in blacks (aHR=1.18; 95%CI: 0.98-1.40).

Additional analyses were performed by investigators that restricted groups to high-risk patients between the ages of 50 and 69 and high-risk patients between the ages of 50 and 59—the age groups for which guidelines suggest aspirin use for cardiovascular disease prevention. In these analyses, results remained similar to those observed in the overall study population ((50 to 69: aHR=0.78; 95% CI: 0.57-1.08 versus aHR=1.10; 95% CI: 0.88-1.39); (50 to 59: aHR=0.74; 95% CI: 0.49-1.12 versus aHR=1.04; 95% CI: 0.77-1.41)).

"We think the reason aspirin use did not have a beneficial effect for African Americans could involve a different genetic response to aspirin therapy and poor control of other risk factors," Fernandez-Jimenez said. "The need to better understand the association between aspirin use, race/ethnicity and socioeconomic status and how these factors play a role in cardiovascular disease are important in light of these findings."

This study, titled “Low-dose Aspirin for Primary Prevention of Cardiovascular Disease: Use Patterns and Impact across Race/Ethnicity in the Southern Community Cohort Study,” was published in the Journal of the American Heart Association.