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

Can exercise actually be bad for you if you don’t get enough sleep? A widely shared claim says yes—that working out while sleep deprived may speed up aging. In this episode, we put that claim under the microscope. We examine the study behind it, unpack how sleep and aging were measured, and explore key statistical ideas like interaction effects and flexible models that can “dance” to the data. With the help of a $400,000 handbag and a man with seven boats, we also break down what it really takes to show that one variable changes the effect of another. What we find: some clear study bloopers, inconsistent modeling results, and interpretations that are flat-out wrong.

Statistical topics

• Measurement error
• Model specification
• Piecewise linear regression
• Regression models
• Residual confounding
• Splines
• Statistical interactions
• Survey design

Methodological morals

• “Before you believe something shocking, ask what had to go wrong to make it true.”
• “If slight modeling changes flip the story, there wasn't much story to begin with.”
• “Unethical Life Pro Tip: If you do not want your analysis critiqued, then just make it impossible to understand.”

Kristin’s Biological Age Calculator

References

• Original Viral Tweet: Ng D. "People who slept under 6 hours and exercised actually aged faster." X. March 9, 2026.
• Holmer B. Does exercise “age you faster” if you don’t sleep enough? Medium. March 16, 2026.
• You Y. Chen Y. Liu R., et al. Inverted U-shaped relationship between sleep duration and phenotypic age in US adults: a population-based study. Sci Rep. 2024;14:6247.
• Levine ME, Lu AT, Quach A, et al. An epigenetic biomarker of aging for lifespan and healthspan. Aging. 2018;10:573-591.

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
• (04:05) - What is NHANES?
• (06:38) - The Sleep Duration Results
• (12:50) - The 2015 Sleep Mystery
• (17:10) - Measuring Biological Aging
• (22:32) - The Penalized Cox Regression
• (29:13) - Sleep and Aging Results
• (31:00) - Cubic Splines and Dancing
• (38:08) - Adding Exercise to the Mix
• (42:16) - Boats, Handbags, and Interaction Effects
• (49:39) - The Cubic Spline Exercise Analysis
• (52:40) - The Opposite Result
• (57:13) - Academic Writing Gone Wrong
• (59:46) - The Writing Makeover
• (01:02:31) - Rating the Claim with Gatorinis