Evaluating the strength and quality of evidence in American Heart Association/American Stroke Association's guidelines for primary stroke prevention.

BACKGROUND

Stroke prevention depends on evidence-based guidelines. This study assessed the strength of recommendations and quality of evidence in AHA/ASA primary stroke prevention guidelines across four editions (2006, 2011, 2014, 2024).

METHODS

Guidelines were reviewed for Class of Recommendation (COR) and Level of Evidence (LOE). Two reviewers independently extracted data using a set protocol; agreement was measured with Cohen's κ. Cochran-Armitage trend tests assessed changes in COR/LOE over time.

RESULTS

Of 35 guideline categories, 8 were descriptive with no formal COR/LOE. The remaining 27 categories yielded 83 recommendations: 45% Class I, 19% Class IIa, 24% Class IIb, and 12% Class III. For evidence quality: 13% LOE A, 24% LOE B-R, 30% LOE B-NR, 5% LOE C-EO, and 28% LOE C-LD. LOE A recommendations fell significantly, from 41% (2006) to 13% (2024) (p < 0.001), while LOE B increased from 33% to 54% (p < 0.001). High-quality (LOE A) evidence was concentrated in pharmacological recommendations for major risk factors, while lifestyle and emerging risk domains relied mostly on LOE B or C evidence.

CONCLUSION

Fewer than half of AHA/ASA primary stroke prevention recommendations carry the top COR, and only 13% rest on high-quality evidence. The drop in LOE A reflects both the guidelines' expansion into newer clinical areas and ongoing challenges in running large randomized controlled trials for those domains.