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In the ATTACK trial, daily 75-mg aspirin did not significantly reduce the combined risk of non-fatal heart attack, non-fatal stroke or cardiovascular death in adults with chronic kidney disease (CKD) who had no prior cardiovascular disease. Aspirin was linked to fewer non-fatal strokes, but the study enrolled far fewer people than planned, and its researchers cautioned against firm conclusions.
A daily 75-mg dose of aspirin did not significantly reduce major vascular events among adults with chronic kidney disease (CKD) and no history of cardiovascular disease, results from the randomized ATTACK trial showed. The findings, presented at the American Society of Nephrology Kidney Week meeting, do not establish aspirin as a routine option for primary prevention in this group, although the trial recorded a significant reduction in non-fatal strokes.
Over a mean 3.1 years of follow-up, a major vascular event occurred in 2.4% of participants assigned aspirin and 3.3% of those assigned no aspirin. The outcome combined non-fatal heart attack, non-fatal stroke and cardiovascular death. The difference did not meet the trial’s primary endpoint for statistical significance: hazard ratio 0.73, 95% confidence interval 0.52–1.03, P=0.077.
When researchers examined the components separately, aspirin was associated with a lower rate of non-fatal stroke (hazard ratio 0.51, 95% CI 0.29–0.90, P=0.021). Differences in the other components did not reach statistical significance. The study also found no statistically significant differences in all-cause mortality or major bleeding, including intracranial, gastrointestinal and other bleeding events.
ATTACK randomized 4,633 participants recruited through primary care practices: 2,317 to daily aspirin and 2,316 to no aspirin, alongside usual care. Outcomes were tracked through routinely collected hospital data. Participants had stage 1 to 4 CKD, no established cardiovascular disease, no elevated bleeding risk and were not taking antiplatelet or anticoagulant drugs at the start of the trial.
Aspirin’s Balance of Benefit and Bleeding
The findings address a practical question for people with CKD: whether their elevated cardiovascular risk makes aspirin useful before a first cardiovascular event. The trial did not show a statistically significant reduction in its combined primary outcome, so its results do not support routinely offering aspirin for primary prevention on this evidence alone. The stroke finding is a secondary component result and does not change the fact that the main endpoint was missed.
That distinction matters because aspirin can reduce clotting but also cause bleeding. Hugh Gallagher, the study’s presenting investigator, said the benefit and harm balance in primary prevention is narrower than in secondary prevention. The trial did not detect a statistically significant difference in major hemorrhage, but that result should not be read as proof that aspirin carries no bleeding risk. The study’s size and enrollment limits also affect how confidently its outcomes can be interpreted.
The findings do not address aspirin use after a person has already had a cardiovascular event. The report says low-dose aspirin is recommended for secondary prevention in CKD patients with a history of cardiovascular disease. People should not start or stop prescribed aspirin based on these results without discussing their circumstances with a qualified clinician.
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Why Researchers Tested Aspirin in CKD
CKD is associated with higher cardiovascular risk, while kidney disease can also complicate decisions about bleeding risk. Gallagher said there remains a substantial burden of cardiovascular disease among people with CKD and relatively few interventions specifically evaluated for them. In the United Kingdom, he estimated around 100,000 heart attacks and strokes each year among people with stage 3 to 5 CKD.
Before ATTACK, the balance of aspirin’s benefits and harms in primary prevention had not been formally evaluated in a trial of significant scale focused on CKD, according to Gallagher. He described the general primary-prevention trade-off as an absolute reduction of about 0.4% in cardiovascular events alongside a similar absolute increase in bleeding. Whether that balance differs for people with CKD was the question the trial set out to test.
The pragmatic, multicenter study enrolled fewer participants than planned. Its population also had specific characteristics: mean age 73, mean estimated glomerular filtration rate of 54 mL/min/1.73 m², and nearly all participants were white. Those details are relevant when judging how well the results apply to other CKD populations.
““We’re not in a place where we should be offering aspirin for primary prevention at this stage, but the question still needs answering.””
— Hugh Gallagher, MBBS, PhD, of Epsom and St Helier University Hospitals NHS Trust
Limits to the ATTACK Findings
The trial enrolled 4,633 people, well below its planned target of 25,000. Gallagher said pandemic-related disruptions contributed to the shortfall. The smaller-than-planned study makes it harder to draw firm conclusions about outcomes that occurred infrequently, including individual cardiovascular events and bleeding. The available report does not provide enough detail to determine how much additional enrollment might have changed the estimates.
The observed reduction in non-fatal stroke was statistically significant, but the overall primary endpoint was not. It is not yet clear whether the stroke result would persist in a larger study or pooled analysis. The findings also apply to the enrolled population: people with stage 1 to 4 CKD who had no prior cardiovascular disease and were not considered at elevated bleeding risk. They do not establish the balance of benefits and harms for people outside those criteria, including those with more advanced CKD.
No statistically significant difference in bleeding was reported, but that does not establish that aspirin has no bleeding effects in this population. The report also does not give enough information to determine whether particular subgroups might benefit or face greater harm.
A Pooled Analysis Is Planned
Gallagher said the ATTACK team is working with the Antithrombotic Trialists’ Collaboration on an individual participant data meta-analysis. Pooling data from trials may help clarify whether aspirin reduces cardiovascular events in people with CKD and how that benefit compares with bleeding risk. No publication date or final analysis results were specified in the report.
Until further evidence is available, the trial’s investigators urged caution about interpreting the findings. The next evidence milestone is the pooled analysis; for now, ATTACK does not show a significant reduction in its main outcome and does not overturn the separate use of aspirin for secondary prevention described in the report.
Key Questions
Did aspirin reduce the main cardiovascular outcome in the trial?
No. Major vascular events occurred in 2.4% of the aspirin group and 3.3% of the group assigned no aspirin, but the difference did not meet the trial’s statistical threshold for its primary endpoint.
Did the trial find any benefit from aspirin?
Aspirin was associated with a statistically significant reduction in non-fatal stroke as an individual outcome. The trial did not find statistically significant differences in the other components of the primary outcome.
Does this mean people with CKD should stop taking prescribed aspirin?
The findings concern primary prevention in people without established cardiovascular disease. The report says low-dose aspirin is recommended for secondary prevention in CKD patients with a history of cardiovascular events. Patients should discuss medication changes with a qualified clinician.
How large was the ATTACK trial?
It randomized 4,633 participants, compared with a planned target of 25,000. The report attributes the enrollment shortfall to pandemic-related disruptions.
What evidence is expected next?
The researchers are working with the Antithrombotic Trialists’ Collaboration on an individual participant data meta-analysis. The report gives no expected release date.
Source: medpagetoday.com
