Two independent AI analyses of the 10 factors that most affect sleep quality — grounded in peer-reviewed primary literature with study citations, effect sizes, and mechanistic explanations.
Same primary research data. Two independent AI interpretations. See where they agree — and where the data points in surprising directions.
A comprehensive synthesis of the primary literature — structured study tables, effect sizes, biological mechanisms, and ranking rationale for all 10 sleep factors.
Opus's independent interpretation — what the data actually proves vs. what people think, with direct study citations and counter-intuitive findings the conventional sleep advice community ignores.
| Rank | Factor | Effect Size | Key Evidence | Why This Rank |
|---|---|---|---|---|
| 1 | Circadian Rhythm & Light Exposure | Czeisler 1999; Lockley 2003 | Master clock — all other factors operate within this framework | |
| 2 | Stress & Cortisol (HPA Axis) | Vgontzas 2001; Meta-analysis 2022 | Most common proximate cause of insomnia; self-reinforcing loop | |
| 3 | Sleep Debt & Chronic Restriction | Van Dongen et al. 2003 | Cumulative, dose-dependent with dangerous subjective blindspot | |
| 4 | Alcohol | Meta-analysis 2024; Roehrs 2001 | Severe sleep architecture disruption; REM suppression | |
| 5 | Temperature & Thermal Regulation | Kräuchi et al. 1999 (Nature) | Direct physiological link to sleep onset; Nature-level evidence | |
| 6 | Caffeine & Adenosine | Drake et al. 2013 | 6h-prior caffeine causes >41 min objective sleep loss | |
| 7 | Blue Light & Screen Exposure | Chang et al. 2015 (PNAS) | Sub-mechanism of circadian pathway; ubiquitous exposure | |
| 8 | Noise & Light Pollution | WHO meta-analysis 2022; Basner 2011 | Disrupts continuity; arousals at 33dB threshold | |
| 9 | Exercise & Physical Activity | Kredlow 2015; Network meta-analysis 2024 | Consistent but smaller effect sizes; indirect pathways | |
| 10 | Meal Timing & Intermittent Fasting | Sutton 2018; Frontiers TRE review 2024 | Smallest effect sizes; indirect circadian pathway |
The most consistent finding across this literature is that humans systematically underestimate their own sleep disruption. Van Dongen (2003) showed subjects restricted to 6h/night lost the ability to perceive their own cognitive impairment — their subjective sleepiness plateaued while performance continued to decline. Drake (2013) showed 400mg caffeine 6 hours before bed reduced objective sleep time by >41 minutes while subjects didn't perceive it. This awareness gap — between actual sleep quality and perceived sleep quality — may be the most important finding in sleep science.