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    "story_id": "mp-2026-10-19-012",
    "source_story_id": "tmp-story-ecg-sleep-depth",
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    "headline": "One ECG Lead Draws a Continuous Sleep-Depth Curve",
    "slug": "one-ecg-lead-draws-a-continuous-sleep-depth-curve",
    "dek": "ECG-SDI moves beyond coarse sleep stages, but its mortality and treatment-response signals remain observational and exploratory.",
    "summary": "ECG-SDI moves beyond coarse sleep stages, but its mortality and treatment-response signals remain observational and exploratory.",
    "body_text": "Conventional staging divides sleep into broad bins. ECG-SDI trains a two-stage model on 12,392 overnight polysomnography records to estimate a continuous depth index from a single ECG lead. The authors report strong correlation with ordered non-REM stages in internal and external data, high REM-classification AUROC, and within-stage variation that the usual labels hide. Derived phenotypes were associated with subjective sleep quality, all-cause mortality and changes after CPAP in separate analyses. Those associations do not prove that the index causes outcomes or that it is ready for clinical decisions; the wearable example is a proof of concept. The work suggests that a ubiquitous cardiac signal may carry a richer overnight profile than a sequence of categorical stages.",
    "why_it_matters": "ECG-SDI moves beyond coarse sleep stages, but its mortality and treatment-response signals remain observational and exploratory.",
    "limitations": [
      "Those associations do not prove that the index causes outcomes or that it is ready for clinical decisions; the wearable example is a proof of concept."
    ],
    "importance": 8,
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    "first_published_at": "2026-10-19T09:00:00.000-04:00",
    "modified_at": "2026-10-19T09:00:00.000-04:00",
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        "text": "ECG-SDI moves beyond coarse sleep stages, but its mortality and treatment-response signals remain observational and exploratory.",
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        "qualification": "Those associations do not prove that the index causes outcomes or that it is ready for clinical decisions; the wearable example is a proof of concept."
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    "source_ids": [
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    "tags": [
      "sleep",
      "ECG",
      "digital biomarkers"
    ],
    "image_url": null,
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  "sources": [
    {
      "source_id": "source-2026-10-19-012",
      "title": "arXiv preprint 2610.23727, original v1",
      "publisher": "arXiv",
      "url": "https://arxiv.org/abs/2610.23727v1",
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      "source_type": "primary_research",
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      "published_at": "2026-10-16T12:43:07.000-04:00",
      "accessed_at": "2026-10-19T08:27:48.782-04:00",
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    "name": "The Machine Press",
    "url": "https://themachinepress.com",
    "description": "A daily newspaper for the age of artificial intelligence."
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  "cite_this_report": {
    "title": "One ECG Lead Draws a Continuous Sleep-Depth Curve",
    "publisher": "The Machine Press",
    "published_at": "2026-10-19T09:00:00.000-04:00",
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