What do chickenpox and shingles have to do with your brain? This week, we dig into two 2025 headline-grabbing studies that link the shingles shot to lower dementia rates. We start in Wales, where a birthday cutoff turned into the perfect natural experiment, and end in the U.S. with a multi-million-person megastudy. Featuring bias-variance Goldilockses, Fozzy-the-Bear regression discontinuities, a Barbie-versus-Oppenheimer showdown for propensity scores – and the hottest rebrand of inverse-probability weighting you’ll ever hear.
Statistical topics
- Absolute vs. relative risk
- Bias–variance tradeoff
- Causal inference
- Censoring
- Confounding
- Fuzzy regression discontinuity design
- Healthy-user bias
- Inverse probability of treatment weighting (IPTW)
- Longitudinal study
- Natural experiment
- Negative controls
- Optimal bandwidth
- Propensity scores
- Selection bias
- Subgroup analysis
- Triangular kernel weights
Methodological morals
- “Propensity scores are the lipstick you put on observational pigs.”
- “Natural experiments are a hot flirtation date with causality.”
References
Detailed Show Notes Page
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) - Intro and first gratuitous mention of sex
- (03:56) - What are shingles, chickenpox, and the vaccines against them?
- (12:30) - Fun facts about the varicella zoster and herpes viruses
- (18:00) - A natural experiment in Wales
- (21:54) - What is the Goldilocks optimal bandwidth?
- (26:17) - Fuzzy regression discontinuity design demystified
- (32:43) - Shingles vaccine vs dementia showdown
- (34:13) - Absolute risk reduction paradox
- (37:44) - Effects for men and women differ
- (41:07) - A giant longitudinal study
- (47:51) - Propensity scores demystified via Barbie and Oppenheimer
- (53:55) - Using propensity scores to make matches
- (58:08) - Inverse probability of treatment weighting demystified via more Barbenheimer
- (01:02:27) - Attempts to rename IPTW for TikTok
- (01:05:59) - Longitudinal study results
- (01:10:00) - Smooch ratings and methodological morals: pigs and hot dates