Does coffee trigger atrial fibrillation — or have doctors been warning people away from caffeine without strong evidence? We dig into two recent randomized clinical trials testing whether caffeinated coffee causes dangerous heart rhythm problems. Along the way, we talk about AFib, survival analysis, intention-to-treat versus as-treated analyses, and one surprisingly elaborate effort to catch clinical trial cheaters with receipts and geolocation tracking. We also explore how a pope may have fueled a European coffee resurgence, why plants make caffeine, and how a game show competition explains hazard ratios.

Statistical topics

• adherence and compliance
• as-treated analysis
• confidence intervals
• Cox proportional hazards regression
• hazard ratios
• intention-to-treat analysis
• micro-randomization
• multiple testing
• PICOT
• pre-registration
• primary vs secondary outcomes
• randomized clinical trials
• sensitivity analyses
• SMART framework
• survival analysis

Methodological morals

• “Never trust conventional wisdom until you see the randomized controlled trial.”
• “Trust your participants, but design the study so that they can be honest about their dishonesty.”

References

• Harrington D, D'Agostino RB Sr, Gatsonis C, et al. New Guidelines for Statistical Reporting in the Journal. N Engl J Med. 2019;381(3):285-286. doi:10.1056/NEJMe1906559
• Marcus GM, Rosenthal DG, Nah G, et al. Acute Effects of Coffee Consumption on Health among Ambulatory Adults. N Engl J Med. 2023;388(12):1092-1100. doi:10.1056/NEJMoa2204737
• Wong CX, Cheung CC, Montenegro G, et al. Caffeinated Coffee Consumption or Abstinence to Reduce Atrial Fibrillation: The DECAF Randomized Clinical Trial. JAMA. 2026;335(4):317-325. doi:10.1001/jama.2025.21056
• @MarcKatzMD’s short video The Pitt- atrial fibrillation cardioversion scene

Kristin and Regina’s online courses:

Demystifying Data: A Modern Approach to Statistical Understanding

Clinical Trials: Design, Strategy, and Analysis

Medical Statistics Certificate Program

Writing in the Sciences

Epidemiology and Clinical Research Graduate Certificate Program

Programs that we teach in:

Epidemiology and Clinical Research Graduate Certificate Program

Find us on:

Kristin - LinkedIn & Twitter/X

Regina - LinkedIn & ReginaNuzzo.com

• (00:00) - - Introduction
• (02:15) - - What is AFib?
• (04:36) - - Frisky Goats and Satan's Bitter Invention
• (10:44) - - How Caffeine Works
• (14:43) - - The CRAVE Trial
• (15:53) - - PICOT: Evaluating the Study Design
• (24:21) - - CRAVE Results
• (31:04) - - Catching the Coffee Cheaters
• (37:58) - - The DECAF Trial
• (42:49) - - Time-to-Event Outcomes
• (44:40) - - Hazard Ratios: Balance Beams Over Shark Tanks
• (48:25) - - DECAF Results: Team Coffee Wins
• (51:57) - - Why Would Coffee Be Protective?
• (55:16) - - Rating the Claim