Sleep and Circadian Biology
Sleep duration tracks with survival in both directions. A meta-analysis of 16 prospective studies with 1.38 million participants found that short sleep was associated with a 12% higher risk of death and long sleep with a 30% higher risk. These are associations from questionnaire-based studies, not proof that changing sleep length changes lifespan.1
Treatable sleep problems are common. An estimated 936 million adults aged 30 to 69 worldwide have obstructive sleep apnea, 425 million of them moderate to severe.2 For chronic insomnia, cognitive behavioral therapy (CBT-I) is the commonly recommended first-line treatment; across 20 trials it shortened the time to fall asleep by about 19 minutes and cut time awake after first falling asleep by about 26 minutes.3
The articles below cover sleep stages, the body clock, apnea and the tools people use to track and improve sleep.
Reading path
Read in this order: the essentials first, then the detail, then the reviews that test popular claims.
Start here
- Sleep and Longevity: Why Sleep Is the Foundation Everything Else Is Built OnWhy sleep duration and quality are linked to heart disease, dementia and mortality, and the habits with the best evidence for better sleep.
- The Sleep Optimization Guide: The Evidence-Based Strategies in One PlaceEvery sleep strategy with real evidence in one place: timing, light, temperature, caffeine and alcohol, and when to see a doctor.
Go deeper
- Sleep Stages and Longevity: Why Deep Sleep and REM Are Non-NegotiableWhat deep sleep and REM sleep do for memory, metabolism and brain clearance, how they change with age, and what affects how much you get.
- Circadian Rhythm and Longevity: How Light, Meal Timing, and Social Jet Lag Age YouHow light exposure, meal timing and irregular sleep schedules shift your body clock, and what the research links to metabolic and heart health.
- Sleep Apnea and Longevity: The Health Risks, Diagnosis and What Treatment DoesHow obstructive sleep apnea strains the heart, brain and metabolism, the warning signs, how it is diagnosed, and the treatments that work.
Evidence checks
- Melatonin: The Sleep Hormone, Its Longevity Biology, and How to Use It CorrectlyHow melatonin works as a timing signal, the doses studied for sleep and jet lag, why more is not better, and what is known about long-term use.
- Sleep Tracking with Wearables: What Your Oura Ring or Whoop Is Actually MeasuringWhat Oura, Whoop and other wearables actually measure during sleep, how accurate their sleep stages are, and how to use the data sensibly.
Sources
- 1Cappuccio FP, et al. "Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies." Sleep. 2010;33(5):585-92. PubMed · DOI
- 2Benjafield AV, et al. "Estimation of the global prevalence and burden of obstructive sleep apnoea: a literature-based analysis." Lancet Respir Med. 2019;7(8):687-698. PubMed · DOI
- 3Trauer JM, et al. "Cognitive Behavioral Therapy for Chronic Insomnia: A Systematic Review and Meta-analysis." Ann Intern Med. 2015;163(3):191-204. PubMed · DOI