Circadian Propensity
Classic morning lark, night owl, or somewhere in between—your chronotype is mostly genetic. Scheduling life around it instead of against it is the easiest health upgrade you'll ever make. Fighting it is the most exhausting.
What this measures
How your DNA shapes circadian propensity.
CLOCK, PER3, and BMAL1 are the core "clock genes" — the molecular oscillators that run a roughly 24-hour rhythm in nearly every cell. CRY1 controls how that internal day aligns with external light. ASMT contributes through melatonin synthesis. The collective network sets whether your biology naturally runs early, late, or in between.
Carriers of CLOCK morning-type variants are associated with earlier natural wake and earlier sleep; carriers of PER3 night-type variants are associated with later natural rhythms. Most clients carry combinations that produce an intermediate but distinct chronotype. CRY1 long-variant carriers are associated with delayed sleep phase — the genuinely-can’t-sleep-before-1am pattern that isn’t lifestyle and isn’t fixable through "better discipline."
Morning bright light shifts the clock earlier; evening blue light shifts it later. Consistent wake time anchors the rhythm more reliably than consistent bedtime. Meal timing influences peripheral clocks in liver and gut. Caffeine timing matters — caffeine at 2pm still affects sleep onset 10 hours later in carriers of slow-CYP1A2 variants.
Fighting your chronotype produces "social jet lag" — chronic mismatch between biology and schedule. Which combination of clock variants you carry decides whether the standard 7am–11pm cadence is biologically congruent or whether structuring your day around an actual chronotype is the missing piece.
Circadian Propensity is one specific finding in this system. Your Genomic Lifestyle Optimization Report shows where your variants place you on the sleep optimization and circadian health spectrum — and what you can do about it: it renders as a dark card with a color marker calibrated to your variants, opening with the gene mechanism and closing with a practical, mechanism-led recommendation.
Want to see what a real Mosaic dark card looks like? Walk through a sample report →
In context
Circadian Rhythm & Timing: the 3-insight cluster.
Circadian Propensity is one finding in a tightly-related cluster. Mosaic sequences the other 2 alongside it so you see the whole biology — not an isolated data point.
Questions people ask
About Circadian Propensity.
More from Sleep Optimization and Circadian Health
Ideal Sleep Duration
Restorative needs range from ~6.5 to ~9 hours between different people. Consistently short-changing your personal number—even by 30 minutes—is often the silent cause of "I sleep 8 hours, but I'm still tired." Maybe you need 8.5. Maybe you only need 7.
Read insight →Melatonin Metabolism
How quickly your body clears melatonin determines whether you wake up groggy from a 1 mg supplement, or can take 5 mg and feel nothing the next morning. Slow metabolizers need lower doses and earlier timing. Fast metabolizers can afford more flexibility.
Read insight →Melatonin Production
Natural evening melatonin rise varies up to 10-fold between people. Low producers struggle with sleep onset, no matter how good their sleep hygiene is. High producers naturally fall asleep early—sometimes inconveniently so. Light exposure and supplement timing finally make sense once you know your baseline.
Read insight →Melatonin Supplement Response
Receptor sensitivity predicts whether melatonin helps you fall asleep faster—or just gives you weird dreams and a morning hangover. If supplements have never worked for you, this might explain why. If they work too well, same answer.
Read insight →Propensity for Daytime Drowsiness
Arousal regulation differs between people. Some stay sharp and alert on 6 hours of sleep; others feel drowsy even after 9. Knowing yours separates "I'm sleeping poorly" from "my daytime alertness drive is genetically lower"—two different problems with different solutions.
Read insight →Risk of Sleep Disruption
Sensitivity to noise, light, and temperature during sleep varies genetically. High-vulnerability individuals need blackout curtains, white-noise machines, and temperature control; low-vulnerability people sleep through fireworks and wonder what all the fuss is about.
Read insight →
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