{"id":"900ea51e-e607-5302-90d9-ce0d3be6a9ab","stable_key":"ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6:caf-clock-human","predicate":"delays","statement":"Caffeine three hours before habitual bedtime delayed the human melatonin rhythm by approximately 40 minutes.","claim_class":"observational","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"5e84cb49-80b3-53f3-ba9d-df7513c400ff","mechanism_event_label":"Caffeine shifted internal timing as well as wakefulness.","subject":{"id":"ef028472-7c33-583d-b52e-40676004d370","slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"},"object":{"id":"84849ca0-e0f3-5400-aaa0-e8d167462aa1","slug":"melatonin-circadian-phase","display_name":"Phase of the endogenous melatonin circadian rhythm","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"5e84cb49-80b3-53f3-ba9d-df7513c400ff","stable_key":"ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6:caf-clock-human-event","event_type":"observed_relationship","label":"Caffeine shifted internal timing as well as wakefulness.","description":"Caffeine three hours before habitual bedtime delayed the human melatonin rhythm by approximately 40 minutes.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"ef028472-7c33-583d-b52e-40676004d370","slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"84849ca0-e0f3-5400-aaa0-e8d167462aa1","slug":"melatonin-circadian-phase","display_name":"Phase of the endogenous melatonin circadian rhythm","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Double-blind within-subject circadian experiment lasting about 49 days.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"A study-specific phase shift, not a fixed effect in every person; endogenous timing differs from clearance of a melatonin supplement.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Caffeine collection; salts, coffee, species and coexposure contexts retain their identities.","comparator":null,"unit":null,"notes":"","entity":{"slug":"caffeine","display_name":"Caffeine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"Caffeine shifted internal timing as well as wakefulness.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Effects of caffeine on the human circadian clock in vivo and in vitro. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26378246/ · DOI 10.1126/scitranslmed.aac5125","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"862eaf15-00d5-51a9-9a9d-215562c4e32f","evidence_kind":"source_excerpt","locator":"Lines 76-82","start_line":76,"end_line":82,"excerpt":"## caf-clock-human\nCaffeine shifted internal timing as well as wakefulness.\nCaffeine three hours before habitual bedtime delayed the human melatonin rhythm by approximately 40 minutes.\nModel: Double-blind within-subject circadian experiment lasting about 49 days.\nLimitations: A study-specific phase shift, not a fixed effect in every person; endogenous timing differs from clearance of a melatonin supplement.\nEvidence access: Primary abstract\nEffects of caffeine on the human circadian clock in vivo and in vitro. · 2015 · https://pubmed.ncbi.nlm.nih.gov/26378246/ · DOI 10.1126/scitranslmed.aac5125","model_system":"Double-blind within-subject circadian experiment lasting about 49 days.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Original curation paraphrase; evidence access stated with the claim.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"40a654db-878c-5471-bc6c-88f4f52599c0","stable_key":"import-ea2f0904-ab2c-5d1e-a3d4-3f7ecdd70cd6","title":"Caffeine: receptors, metabolism, nutrient interactions, adaptation and discovery questions (2026-09-18)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text.","file_path":"","sha256":"780d73d4abd45a0284d2cc0c646dbe8432ae347362891a4b98a19a61341a7325","revision_id":"f36ffb0a-d6df-522f-b783-5e30214b9e26","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}