When should you sleep?
Your personalized sleep schedule, computed from your chronotype, your cognitive goals, and the 90-minute architecture of human sleep. Built on the UK Biobank study of 224,714 adults and a meta-analysis of 49 cohort studies.
Tell us about your sleep.
The first section establishes your chronotype — your genetic tendency toward mornings or evenings. The second measures your current sleep quality. The third defines what you want to optimize for. Every answer refines the recommendation in real-time.
How the Sleep-Cognition Optimizer computes your schedule.
The LifeByLogic Sleep-Cognition Optimizer (LBL-SCO) is a four-stage optimization that takes your chronotype, current sleep, and cognitive goals — and returns a sleep schedule aligned with peer-reviewed research on circadian biology and sleep architecture.
Stage 1 — Chronotype Inference
Four questions — ideal wake time, ideal bedtime, morning alertness, and peak cognitive time — are scored against the Horne-Östberg MEQ framework. Scores map to one of five chronotypes: definite morning, moderate morning, intermediate, moderate evening, or definite evening. This is an abbreviated version of the full 19-item MEQ, calibrated to give reliable results in under a minute.
Stage 2 — Target Sleep Duration
Based on meta-analyses of 49 cohort studies, optimal sleep for cognitive performance falls between 7 and 8 hours for most adults. The optimizer targets five complete 90-minute cycles (7.5 hours) as the primary schedule — extending to six cycles (9 hours) for people who report current undersleeping or high sleep latency.
Stage 3 — Cycle-Aligned Wake Time
Waking at the end of a complete 90-minute cycle (during light sleep) dramatically reduces sleep inertia compared to waking mid-cycle (during deep sleep or REM). The optimizer sets the wake time to the closest cycle boundary that aligns with your cognitive peak-need and chronotype.
Stage 4 — Peak Performance Windows
For each chronotype, research has mapped consistent peak windows for different cognitive domains:
Working memory and focus peak 2–4 hours after waking for morning types, 5–7 hours after waking for evening types. Creative and divergent thinking is often strongest in the opposite of your peak window — when your executive control is slightly lower and looser associations emerge. Physical performance peaks in the late afternoon for most chronotypes, though evening types show later peaks. Memory consolidation happens primarily during deep sleep in the first third of the night — disrupting this period has outsized cognitive costs.
Note: The Sleep-Cognition Optimizer is an educational tool for planning your sleep schedule. It is not a treatment for insomnia or sleep disorders. If you have persistent sleep problems, consult a sleep medicine specialist.
The research behind the optimizer.
- Ahn S, et al. Chronotype, sleep duration, and risk of cognitive decline: a large-scale cohort study of 224,714 adults. 2024. Finding: 7–8 hours sleep + morningness type showed lowest risk of cognitive decline.
- Young V, Bernal R, Baril AA, et al. Long sleep duration, cognitive performance, and the moderating role of depression: a cross-sectional analysis in the Framingham Heart Study. Alzheimer's & Dementia. 2025;21(4):e70160. doi:10.1002/alz.70160
- Prolonged sleep duration as a predictor of cognitive decline: A meta-analysis encompassing 49 cohort studies. Sleep Medicine Reviews. 2024. Finding: both short (<6h) and long (>9h) sleep durations associated with worse cognitive outcomes.
- Horne JA, Östberg O. A self-assessment questionnaire to determine morningness-eveningness in human circadian rhythms. International Journal of Chronobiology. 1976;4(2):97-110. The validated chronotype instrument adapted for this tool.
- U-shaped association between sleep duration and long-term cognitive decline trajectories in a national cohort. Scientific Reports. 2025. CHARLS cohort n=8,668. Found OR 1.17 for short sleep, 1.57 for long sleep vs optimal 7–8h.
- Sleep Duration and Executive Function in Adults. Current Neurology and Neuroscience Reports. 2023. Established quadratic relationship between sleep duration and executive function.
- Chronotype and synchrony effects in human cognitive performance: A systematic review. Chronobiology International. 2025. Protocol PROSPERO CRD42024498808.
- The effects of time of day and chronotype on cognitive and physical performance in healthy volunteers. 2018. Established peak performance timing differences between early and late chronotypes using Munich ChronoType Questionnaire.
- Huang T, Beydoun MA, Kianersi S, Redline S, Launer LJ. Multi-dimensional sleep health and dementia risk: A prospective study in the UK Biobank. BMC Medicine. 2025;23:410.
Questions about the optimizer.
Partially. Chronotype has a strong genetic component (heritability ~50%), but it also shifts with age and light exposure. Most people become gradually more morning-oriented after age 40–50. Strategic light exposure (bright morning light, dim evening light) can shift your chronotype by 30–60 minutes. But you cannot turn a definite evening type into a definite morning type — and fighting your chronotype chronically has cognitive and metabolic costs.
Sleep happens in roughly 90-minute cycles. 7.5 hours = 5 complete cycles, which means you wake during the lighter end of a cycle. 8 hours leaves you mid-cycle at wake time, often during deep sleep or REM — which produces strong sleep inertia (grogginess). 7.5 hours of cycle-aligned sleep often feels better than 8 hours of cycle-misaligned sleep.
Three strategies help: (1) Bright light exposure for 20–30 minutes immediately after waking shifts your circadian rhythm earlier over 2–3 weeks. (2) No screens 90 minutes before bed prevents further delay. (3) Strategic caffeine timing — caffeine 90 minutes after waking, not immediately, works with your natural cortisol rhythm instead of against it. Crucially: your peak cognitive performance window may still fall in the afternoon or evening. Schedule your hardest work for that window even if you must be at work earlier.
Not directly. Shift work disrupts circadian rhythms in ways this tool cannot model. If you work rotating or night shifts, consult a sleep medicine specialist; the literature on shift-work sleep optimization is its own specialty.
Sleep duration and quality are two of the highest-impact factors in the Brain Age Index. Poor sleep can add up to 3 years to your brain age; optimized sleep can protect against that. Use this tool to design the sleep side; use the Brain Age Index to see how it compounds with other factors.
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