Russell Foster | Your Body Clock and Its Essential Roles in Good Health and Sleep | Talks at Google

Talks at Google

Introduction and Speaker Background

Russell Foster: Professor of circadian neuroscience, Oxford University
Head of Nuffield Laboratory of Ophthalmology
Founder/director of Sleep and Circadian Research Institute
Published 290+ scientific papers, multiple awards
Latest book: "Lifetime: Your Body Clock and Its Essential Roles in Good Health and Sleep" (Yale University Press)
Focus: how modern life disrupts ancient circadian biology

Earth rotates every 24 hours, creating distinct ecological states (night/day)
All life evolved responses to these different states
Human physiology requires different underpinning for sleep vs. consciousness periods
Body clock anticipates 24-hour light-dark cycle, fine-tunes physiology in advance

Blood pressure: drops before sleep, rises sharply before wake for oxygen/glucose delivery
Growth hormone: released first half of night for tissue repair
Core body temperature: drops for sleep, rises for increased metabolism/muscle efficiency
Cortisol: peaks morning for activity preparation
Testosterone: released morning window, sperm quality highest this phase
Information processing: lowest early morning, peaks late morning/early afternoon

Suprachiasmatic nuclei (SCN): master clock in hypothalamus
~50,000 individual cells, each generating 24-hour circadian rhythm
Clock genes produce proteins → form complex → enter nucleus → inhibit further activation → cycle repeats
Discovery: every cell in body has capacity for 24-hour oscillation (peripheral clocks)
Billions of cellular oscillators organized throughout organ systems
Clock gene variations linked to morning/evening chronotypes

Adult peak performance: 11 AM - 12 noon (late morning/early afternoon)
Teenagers peak 2 hours later than adults
Implications: demanding subjects (math, sciences) taught when students still waking up
Exam success improves later in day for teenagers
4 AM cognitive abilities: -20 (worse than legally drunk at -15)
Drew Dawson study: early morning driving worse than drunk driving
100,000-300,000 US freeway crashes from early morning cognitive impairment

31 studies, 12,000 stroke patients: 50% increase in stroke risk 6 AM - 12 noon
Oxford Vascular Study confirms sharp morning peak
Anti-hypertensive medication timing critical
Evening dosing more effective than morning dosing
10-12 year study: ~50% difference in death rates (bedtime vs. morning medication)

1993 study: 118 children chemotherapy timing
- Evening schedule: 70% survival
- Morning schedule: 35% survival
Ovarian cancer treatment schedules A vs B (same drugs, different times)
- Schedule A: 45% five-year survival
- Schedule B: 10% five-year survival
WHO declares shift work "probable carcinogen"
Nurses doing night shifts: higher breast, endometrial, colorectal cancer rates
Female flight attendants: increased breast cancer, malignant melanoma
Male pilots: higher prostate cancer rates
One night without sleep: 28% reduction in natural killer cell activity

Every aspect immune response regulated by circadian system
2016 H1N1 vaccination study (70+ years old)
- Morning vaccination: robust antibody response (0 to 400)
- Afternoon vaccination (3-5 PM): threefold lower response
COVID-19 timing studies ongoing at Harvard and Oxford

Mice nocturnal, humans diurnal (12-hour physiology difference)
2020 stroke drug study example:
- Mouse daytime testing: drug effective
- Human daytime testing: drug ineffective
- Mouse nighttime testing: drug ineffective
- Human nighttime dosing would likely be effective
Missing drug discoveries due to timing mismatches

Emotional: mood fluctuations, irritability, anxiety, loss of empathy, frustration, risk-taking, impulsivity
Cognitive: impaired multitasking, memory consolidation, attention, concentration, communication, decision-making, productivity, motor performance
Increased stimulant/sedative use, potential illegal drug progression

Jan Bourne study: problem-solving task performance
- Morning task, afternoon performance: 20% solved
- Morning task, kept awake all night, next afternoon: 20% solved
- Morning task, normal sleep, next afternoon: 60-70% solved
Sleep promotes novel solutions to complex problems

80-100% individuals with mental health diagnosis have significant sleep disruption
Shared neurotransmitter systems and brain circuits between sleep and mental illness
Feedback loop: mental illness → sleep disruption → worsened symptoms → more disruption
Sleep stabilization as therapeutic target

Genetics: clock gene variations affect morning/evening preference
Age changes: later bedtimes through teens/early 20s, then earlier with age
2-hour difference between peak teenage and adult timing
Sex differences: men tend to stay up later longer than women
Light exposure: morning light advances clock, evening light delays clock
Modern lifestyle: missing morning light, excess evening light shifts to later times
Social media/screen time compounds late sleep patterns

pRGCs maximally sensitive to blue light
Blue light glasses don't reduce blue light exposure, just filter other wavelengths
Australian/New Zealand ophthalmologists: no direct evidence for blue glasses effectiveness
Cataract lens study: blue-blocking vs UV-blocking showed no sleep-wake timing differences
Likely placebo effect rather than physiological benefit

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