{
  "schema_version": 1,
  "id": "sleep-variability-cognition-2026",
  "canonical_url": "https://brali-lifeos.github.io/evidence/sleep-variability-cognition-2026/",
  "json_url": "https://brali-lifeos.github.io/evidence/sleep-variability-cognition-2026/index.json",
  "decision": "watch",
  "decision_label": "Watch, do not prescribe",
  "reviewed_at": "2026-08-18",
  "reviewed_by": "Brali Evidence Reviewer",
  "source": {
    "title": "The association between sleep variability and cognitive function: A systematic review and meta analysis",
    "url": "https://www.sciencedirect.com/science/article/abs/pii/S0165032725019238",
    "type": "meta-analysis",
    "doi": "10.1016/j.jad.2025.120481",
    "citation_text": "Xia Y, He S, Sun Z, Wang F. Journal of Affective Disorders. 2026;393(Pt B):120481.",
    "study_design": "Systematic review and three-level meta-analysis of 20 published articles, 103 effect sizes, total N=15,828.",
    "population": "Human participants across age groups represented in the included observational literature; the association was stronger in older adults than in adolescents and middle-aged adults.",
    "intervention_or_exposure": "Night-to-night sleep variability or irregularity across sleep measures.",
    "outcomes": [
      "Cognitive performance"
    ]
  },
  "supported_claim": "Across the included literature, greater sleep variability was associated with poorer cognitive performance on average, with a small pooled correlation and age moderating the association.",
  "unsupported_or_overstated_claims": [
    "Sleep irregularity has been shown to cause cognitive decline.",
    "Making sleep timing more regular has been shown by this meta-analysis to improve cognition.",
    "A fixed bedtime or wake-time tolerance can be prescribed from this evidence.",
    "The association justifies treatment or dementia-prevention claims for an individual."
  ],
  "limitations": [
    "The reviewed evidence is primarily association evidence and does not establish the direction of causality.",
    "Sleep variability and cognition were operationalized in different ways across studies.",
    "The pooled association was small (r=-0.12 in the authors' analysis).",
    "Age moderated the association, so a single population-wide claim would hide meaningful differences.",
    "The publisher abstract and bibliographic record were directly reviewed for this Brali decision; a causal behavior-change protocol is deliberately not proposed from this source alone."
  ],
  "target_hack_ids": [],
  "target_protocol_ids": [],
  "risk_flags": [
    "health"
  ],
  "notes": "Use this source to justify maintaining Sleep & Circadian Rhythm as a research Topic and to motivate further intervention-focused discovery. Do not publish regular sleep improves cognition from this evidence."
}