In this episode:

• Why major changes in sleep science often take years to become visible
• How scientific knowledge becomes more nuanced instead of simply replacing “wrong” answers with “right” ones
• Why no single sleep stage should automatically be treated as the only stage that matters
• REM sleep, deep sleep and the brain's overnight fluid dynamics
• What p-values are trying to tell us about uncertainty
• Why replication and converging evidence matter
• The problem with treating scientific revision as scientific failure
• What “normal sleepers” means in device-validation research
• Why sleep trackers may mistake motionless wakefulness for sleep
• Why disagreement between a wearable, a sleep lab and your memory does not have a simple answer
• How to think about consumer sleep technology as a measurement tool rather than a truth machine
• The evidence for later middle- and high-school start times
• Teen driving safety and later school schedules
• Why sleep and circadian researchers favor permanent standard time
• The conflict between circadian biology and our preference for brighter evenings
• Where the idea of a 90-minute sleep cycle comes from
• Why 90 minutes is an approximation, not a sleep-planning rule
• How the human appetite for “secret knowledge” turns useful observations into rigid sleep hacks

Dr. Michael Grandner is a licensed clinical psychologist and behavioral sleep medicine specialist at the University of Arizona. He directs the Sleep and Health Research Program and the Behavioral Sleep Medicine Clinic at Banner – University Medical Center Tucson, with appointments across psychiatry, medicine, psychology and related programs. His research spans insufficient sleep, sleep health, cardiometabolic and neurocognitive outcomes, social and environmental influences on sleep, health disparities and behavioral interventions.

On the day this episode was released — June 3, 2024 — Grandner was receiving the Associated Professional Sleep Societies' Diversity, Equity and Inclusion Leadership Award, recognizing contributions to broadening access and representation and reducing sleep-health disparities. The award has since been renamed the APSS Inclusive Leadership Award.

• Michael Grandner — University of Arizona College of Medicine
• APSS Inclusive Leadership Award and past recipients
• Dementia and Sleep: It's Not Just Deep Sleep That Counts with Dr. Laura Bojarskaitė
• Bojarskaitė et al.: Sleep cycle-dependent vascular dynamics and predicted cerebrospinal-fluid transport
• 2025 meta-analysis: consumer wrist-worn sleep trackers compared with polysomnography
• 2026: Consumer sleep technologies — what we know and what comes next
• AASM position statement on later middle- and high-school start times
• Adolescent sleep, school start times and teen motor-vehicle crashes
• AASM: Permanent standard time is the optimal choice for health and safety
• Review of human sleep architecture and 90–110 minute NREM/REM cycles