Efficiency

• Caffeine

  Keep caffeine early, and keep late doses small.

• Bed

  Get into bed only when you are sleepy.

• Alcohol

  Keep drinks few, and finish well before bed.

• Noise

  Keep the bedroom quiet and try earplugs.

• Temperature

  Keep your bedroom cool and avoid overheating.

• Exercise

  Train at whatever time you will actually keep.

What It Is

How much of your time in bed you actually spend asleep.

Why It Matters

Sleep efficiency is the share of your time in bed spent asleep, the standard measure of sleep continuity. Sleep-quality guidelines treat 85% or higher as the threshold for good sleep in adults, and that is a guideline convention rather than a line where risk suddenly changes. Chasing 100% is not the goal either: falling asleep the instant you lie down and never stirring can be a sign of sleep deprivation rather than great sleep. Treat efficiency as a floor to clear, not a number to maximize.

Efficiency measures continuity, not quantity: you can spend nine hours in bed and still score poorly. Fragmented sleep, from a long time to fall asleep or repeated awakenings, blunts the deep and REM stages that drive physical and cognitive recovery. The long-term evidence is mixed. Large cohorts that have followed efficiency through to death disagree on whether it carries a signal of its own, and the studies able to tell one band from another place what signal there is in genuinely broken sleep, well below the guideline threshold rather than just under it. Where it does show up, low efficiency may raise mortality risk. Treat efficiency as a useful continuity marker, but a weaker and less settled one than how long or how regularly you sleep.

Aim to clear 85%. The levers are mostly behavioral: keep a consistent schedule, reserve the bed for sleep, get out of bed if you have been awake a while, and resist padding your time in bed to force more sleep. If efficiency stays low even with enough time in bed, treat that as the signal to work on sleep quality rather than to spend longer lying awake.

• Ohayon, M. et al. (2017). National Sleep Foundation's sleep quality recommendations: First report. Sleep Health. doi.org/10.1016/j.sleh.2016.11.006
• Yan, B. et al. (2021). Objective Sleep Efficiency Predicts Cardiovascular Disease in a Community Population: The Sleep Heart Health Study. Journal of the American Heart Association. doi.org/10.1161/JAHA.120.016201
• Liang, Y.Y. et al. (2023). Joint Associations of Device-Measured Sleep Duration and Efficiency With All-Cause and Cause-Specific Mortality: A Prospective Cohort Study of 90 398 UK Biobank Participants. The Journals of Gerontology: Series A. doi.org/10.1093/gerona/glad108
• Saint-Maurice, P.F. et al. (2024). Associations between actigraphy-measured sleep duration, continuity, and timing with mortality in the UK Biobank. Sleep. doi.org/10.1093/sleep/zsad312
• Furukawa, Y. et al. (2024). Components and Delivery Formats of Cognitive Behavioral Therapy for Chronic Insomnia in Adults: A Systematic Review and Component Network Meta-Analysis. JAMA Psychiatry. doi.org/10.1001/jamapsychiatry.2023.5060
• Steinmetz, L. et al. (2024). Network meta-analysis examining efficacy of components of cognitive behavioural therapy for insomnia. Clinical Psychology Review. doi.org/10.1016/j.cpr.2024.102507