--- title: "KnowYourPrime Evidence Registry" description: "KnowYourPrime Evidence Registry: permanent, citable records rating the published evidence on wearable health measurements, from blood oxygen and HRV to sleep and readiness scores. Fixed IDs, versions and full study lists." url: https://knowyourprime.com/evidence --- KnowYourPrime # KnowYourPrime Evidence Registry Permanent, citable records of how strong the published evidence is for specific claims about wearable health metrics. Each finding has a fixed ID, a rating set by a fixed rule, the studies behind it and a dated version history. 25 findings [Full index as JSON](https://knowyourprime.com/evidence.json) [All desk claims as JSON](https://knowyourprime.com/claims.json) [Rating changes as JSON](https://knowyourprime.com/rating-changes.json) [Methodology](https://knowyourprime.com/methodology) [Data: CC BY 4.0](https://creativecommons.org/licenses/by/4.0/) ## Findings Showing all 25 findings | ID | Finding | Measurement | Rating | Version | Reviewed | | --- | --- | --- | --- | --- | --- | | KYP-ER-0001 | [Smartwatch Blood Oxygen (SpO2) Accuracy Against Arterial Blood (SaO2)](https://knowyourprime.com/evidence-wearable-blood-oxygen-accuracy) | Blood oxygen (SpO2) | Uncertain | 1.1 | October 25, 2026 | | KYP-ER-0002 | [Pulse Oximeter Accuracy and Skin Tone](https://knowyourprime.com/evidence-pulse-oximeter-skin-tone-bias) | Blood oxygen (SpO2) | Uncertain | 1.0 | October 24, 2026 | | KYP-ER-0003 | [Wearable HRV Accuracy Against ECG](https://knowyourprime.com/evidence-wearable-hrv-accuracy) | Heart rate variability (HRV) | Uncertain | 1.0 | October 24, 2026 | | KYP-ER-0004 | [Chest Strap HRV Accuracy Against ECG](https://knowyourprime.com/evidence-chest-strap-hrv-accuracy) | Heart rate variability (HRV) | Established | 1.0 | October 24, 2026 | | KYP-ER-0005 | [Readiness and Recovery Score Validity](https://knowyourprime.com/evidence-readiness-recovery-score-validity) | Readiness and recovery scores | Uncertain | 1.0 | October 24, 2026 | | KYP-ER-0006 | [Work Stress and HRV](https://knowyourprime.com/evidence-work-stress-hrv) | Heart rate variability (HRV) | Emerging | 1.0 | October 24, 2026 | | KYP-ER-0007 | [Wearable Sleep Tracking Accuracy Against a Sleep Lab](https://knowyourprime.com/evidence-wearable-sleep-tracking-accuracy) | Sleep | Uncertain | 1.0 | October 24, 2026 | | KYP-ER-0008 | [Under-Mattress Sleep Sensor Accuracy](https://knowyourprime.com/evidence-under-mattress-sleep-sensor-accuracy) | Sleep | Uncertain | 1.0 | October 24, 2026 | | KYP-ER-0009 | [Wearable Heart Rate Accuracy](https://knowyourprime.com/evidence-wearable-heart-rate-accuracy) | Heart rate | Established | 1.0 | October 24, 2026 | | KYP-ER-0010 | [Wearable Calorie and Energy Expenditure Accuracy](https://knowyourprime.com/evidence-wearable-calorie-accuracy) | Calories (energy expenditure) | Uncertain | 1.1 | October 24, 2026 | | KYP-ER-0011 | [Wearable VO2 Max Estimate Accuracy](https://knowyourprime.com/evidence-wearable-vo2-max-accuracy) | VO2 max (cardio fitness) | Emerging | 1.0 | October 24, 2026 | | KYP-ER-0012 | [Do Activity Trackers Make People More Active?](https://knowyourprime.com/evidence-do-activity-trackers-increase-activity) | Physical activity | Uncertain | 1.0 | October 24, 2026 | | KYP-ER-0013 | [Overnight HRV Drop Before an Infection](https://knowyourprime.com/evidence-sudden-hrv-drop-before-illness) | Heart rate variability (HRV) | Emerging | 1.0 | October 24, 2026 | | KYP-ER-0014 | [Normal HRV Range by Age](https://knowyourprime.com/evidence-normal-hrv-by-age) | Heart rate variability (HRV) | Established | 1.0 | October 24, 2026 | | KYP-ER-0015 | [VO2 Max by Age and Sex: US Reference Standards](https://knowyourprime.com/evidence-vo2-max-by-age-reference) | VO2 max (cardio fitness) | Established | 1.1 | October 24, 2026 | | KYP-ER-0016 | [Wearable Sleep Stage Accuracy](https://knowyourprime.com/evidence-wearable-sleep-stage-accuracy) | Sleep | Uncertain | 1.0 | October 24, 2026 | | KYP-ER-0017 | [Can Blood Oxygen Monitoring Rule Out Sleep Apnea?](https://knowyourprime.com/evidence-oximetry-sleep-apnea-screening) | Blood oxygen (SpO2) | Uncertain | 1.0 | October 24, 2026 | | KYP-ER-0018 | [Smartwatch Blood Oxygen Accuracy at Altitude](https://knowyourprime.com/evidence-smartwatch-blood-oxygen-at-altitude) | Blood oxygen (SpO2) | Uncertain | 1.0 | October 24, 2026 | | KYP-ER-0019 | [Blood Oxygen Readings With Poor Circulation](https://knowyourprime.com/evidence-blood-oxygen-poor-circulation) | Blood oxygen (SpO2) | Uncertain | 1.2 | October 24, 2026 | | KYP-ER-0020 | [Accuracy of Smartwatches With a Built-In Blood Pressure Cuff](https://knowyourprime.com/evidence-smartwatch-cuff-blood-pressure-accuracy) | Blood pressure | Uncertain | 1.0 | October 24, 2026 | | KYP-ER-0021 | [Cuffless Blood Pressure Accuracy at Night](https://knowyourprime.com/evidence-cuffless-blood-pressure-at-night) | Blood pressure | Uncertain | 1.0 | October 24, 2026 | | KYP-ER-0022 | [Do Calibrated Cuffless Blood Pressure Readings Track Real Changes?](https://knowyourprime.com/evidence-calibrated-cuffless-blood-pressure-tracking) | Blood pressure | Uncertain | 1.0 | October 24, 2026 | | KYP-ER-0023 | [Apple Watch Blood Oxygen Accuracy Against Medical Devices](https://knowyourprime.com/evidence-apple-watch-blood-oxygen-accuracy) | Blood oxygen (SpO2) | Uncertain | 1.2 | October 27, 2026 | | KYP-ER-0024 | [Oura Ring HRV Accuracy Against ECG](https://knowyourprime.com/evidence-oura-hrv-accuracy) | Heart rate variability (HRV) | Established | 1.0 | October 24, 2026 | | KYP-ER-0025 | [Apple Watch HRV Accuracy Against ECG and Chest Straps](https://knowyourprime.com/evidence-apple-watch-hrv-accuracy) | Heart rate variability (HRV) | Uncertain | 1.0 | October 24, 2026 | ## What a finding is A finding is one question about a wearable measurement, such as whether a smartwatch blood oxygen reading matches arterial blood, rated against every study KnowYourPrime has scored for it. The record states the question, the rating, a plain answer, the key numbers, what the finding does and does not cover, its limitations and the full list of studies with their roles. The long-form analysis behind each finding sits on its research desk, linked from the finding; the Registry is the citable record of where that analysis stands. ## How ratings are set Each study is assigned a role for the claim: an anchor the rating can rest on, a supporting study, a conflicting study or a null result. A fixed rule turns those roles into one of five ratings, so the same evidence always produces the same rating. The rule and its version are shown on every finding. - Established Strong, consistent evidence supports the claim. - Emerging Evidence currently favors the claim, but more confirmation is needed. - Uncertain Evidence is conflicting, inconsistent, or difficult to interpret. - Insufficient Too little evidence exists to reach a conclusion. - Unsupported Existing evidence does not support the claim. The full rule is set out in the [methodology](https://knowyourprime.com/methodology) and [how KnowYourPrime interprets evidence](https://knowyourprime.com/how-we-interpret). ## Versions, review dates and corrections A finding always carries the current rating on its research desk. When the evidence moves the rating, the finding gets a new major version (2.0, 3.0); when its text is revised, a new minor version (1.1, 1.2). Each version is dated and says what changed, and earlier versions stay listed. Errors are corrected the same way, as a new dated version, and can be reported to [corrections@knowyourprime.com](mailto:corrections@knowyourprime.com). ## How to cite a finding KnowYourPrime Evidence Registry, Finding \[ID\], version \[version\], reviewed \[date\]. \[URL\] Every finding prints its own completed citation line, and the same line appears in its JSON and Markdown versions. Cite the page URL, not the JSON or Markdown file. ```json { "@context": "https://schema.org", "@type": "CollectionPage","dateModified":"2026-10-28", "@id": "https://knowyourprime.com/evidence#registry", "name": "KnowYourPrime Evidence Registry", "license": "https://creativecommons.org/licenses/by/4.0/", "url": "https://knowyourprime.com/evidence", "description": "Permanent, citable records of how strong the published evidence is for specific claims about wearable health metrics.", "publisher": { "@type": "Organization", "@id": "https://knowyourprime.com/#organization", "name": "KnowYourPrime", "url": "https://knowyourprime.com" }, "mainEntity": { "@type": "ItemList", "numberOfItems": 25, "itemListElement": [ { "@type": "ListItem", "position": 1, "url": "https://knowyourprime.com/evidence-wearable-blood-oxygen-accuracy", "name": "KYP-ER-0001: Smartwatch Blood Oxygen (SpO2) Accuracy Against Arterial Blood (SaO2)" }, { "@type": "ListItem", "position": 2, "url": "https://knowyourprime.com/evidence-pulse-oximeter-skin-tone-bias", "name": "KYP-ER-0002: Pulse Oximeter Accuracy and Skin Tone" }, { "@type": "ListItem", "position": 3, "url": "https://knowyourprime.com/evidence-wearable-hrv-accuracy", "name": "KYP-ER-0003: Wearable HRV Accuracy Against ECG" }, { "@type": "ListItem", "position": 4, "url": "https://knowyourprime.com/evidence-chest-strap-hrv-accuracy", "name": "KYP-ER-0004: Chest Strap HRV Accuracy Against ECG" }, { "@type": "ListItem", "position": 5, "url": "https://knowyourprime.com/evidence-readiness-recovery-score-validity", "name": "KYP-ER-0005: Readiness and Recovery Score Validity" }, { "@type": "ListItem", "position": 6, "url": "https://knowyourprime.com/evidence-work-stress-hrv", "name": "KYP-ER-0006: Work Stress and HRV" }, { "@type": "ListItem", "position": 7, "url": "https://knowyourprime.com/evidence-wearable-sleep-tracking-accuracy", "name": "KYP-ER-0007: Wearable Sleep Tracking Accuracy Against a Sleep Lab" }, { "@type": "ListItem", "position": 8, "url": "https://knowyourprime.com/evidence-under-mattress-sleep-sensor-accuracy", "name": "KYP-ER-0008: Under-Mattress Sleep Sensor Accuracy" }, { "@type": "ListItem", "position": 9, "url": "https://knowyourprime.com/evidence-wearable-heart-rate-accuracy", "name": "KYP-ER-0009: Wearable Heart Rate Accuracy" }, { "@type": "ListItem", "position": 10, "url": "https://knowyourprime.com/evidence-wearable-calorie-accuracy", "name": "KYP-ER-0010: Wearable Calorie and Energy Expenditure Accuracy" }, { "@type": "ListItem", "position": 11, "url": "https://knowyourprime.com/evidence-wearable-vo2-max-accuracy", "name": "KYP-ER-0011: Wearable VO2 Max Estimate Accuracy" }, { "@type": "ListItem", "position": 12, "url": "https://knowyourprime.com/evidence-do-activity-trackers-increase-activity", "name": "KYP-ER-0012: Do Activity Trackers Make People More Active?" }, { "@type": "ListItem", "position": 13, "url": "https://knowyourprime.com/evidence-sudden-hrv-drop-before-illness", "name": "KYP-ER-0013: Overnight HRV Drop Before an Infection" }, { "@type": "ListItem", "position": 14, "url": "https://knowyourprime.com/evidence-normal-hrv-by-age", "name": "KYP-ER-0014: Normal HRV Range by Age" }, { "@type": "ListItem", "position": 15, "url": "https://knowyourprime.com/evidence-vo2-max-by-age-reference", "name": "KYP-ER-0015: VO2 Max by Age and Sex: US Reference Standards" }, { "@type": "ListItem", "position": 16, "url": "https://knowyourprime.com/evidence-wearable-sleep-stage-accuracy", "name": "KYP-ER-0016: Wearable Sleep Stage Accuracy" }, { "@type": "ListItem", "position": 17, "url": "https://knowyourprime.com/evidence-oximetry-sleep-apnea-screening", "name": "KYP-ER-0017: Can Blood Oxygen Monitoring Rule Out Sleep Apnea?" }, { "@type": "ListItem", "position": 18, "url": "https://knowyourprime.com/evidence-smartwatch-blood-oxygen-at-altitude", "name": "KYP-ER-0018: Smartwatch Blood Oxygen Accuracy at Altitude" }, { "@type": "ListItem", "position": 19, "url": "https://knowyourprime.com/evidence-blood-oxygen-poor-circulation", "name": "KYP-ER-0019: Blood Oxygen Readings With Poor Circulation" }, { "@type": "ListItem", "position": 20, "url": "https://knowyourprime.com/evidence-smartwatch-cuff-blood-pressure-accuracy", "name": "KYP-ER-0020: Accuracy of Smartwatches With a Built-In Blood Pressure Cuff" }, { "@type": "ListItem", "position": 21, "url": "https://knowyourprime.com/evidence-cuffless-blood-pressure-at-night", "name": "KYP-ER-0021: Cuffless Blood Pressure Accuracy at Night" }, { "@type": "ListItem", "position": 22, "url": "https://knowyourprime.com/evidence-calibrated-cuffless-blood-pressure-tracking", "name": "KYP-ER-0022: Do Calibrated Cuffless Blood Pressure Readings Track Real Changes?" }, { "@type": "ListItem", "position": 23, "url": "https://knowyourprime.com/evidence-apple-watch-blood-oxygen-accuracy", "name": "KYP-ER-0023: Apple Watch Blood Oxygen Accuracy Against Medical Devices" }, { "@type": "ListItem", "position": 24, "url": "https://knowyourprime.com/evidence-oura-hrv-accuracy", "name": "KYP-ER-0024: Oura Ring HRV Accuracy Against ECG" }, { "@type": "ListItem", "position": 25, "url": "https://knowyourprime.com/evidence-apple-watch-hrv-accuracy", "name": "KYP-ER-0025: Apple Watch HRV Accuracy Against ECG and Chest Straps" } ] } } ``` ```json { "@context": "https://schema.org", "@type": "Dataset", "@id": "https://knowyourprime.com/evidence#dataset", "name": "KnowYourPrime evidence ratings for wearable health metrics", "description": "Evidence ratings for claims about consumer wearable health measurements, including HRV, resting heart rate, sleep staging, blood oxygen, VO2 max, calories, readiness scores and blood pressure. Two files: the Evidence Registry, with permanent versioned findings that carry a written conclusion, scope, limitations and a study list, and the Research Desk claims, with every rated claim, its current rating, the rule reasons behind it and its studies by role. Ratings are computed from the studies by fixed rules on a five-level scale from Established to Unsupported.", "url": "https://knowyourprime.com/evidence", "license": "https://creativecommons.org/licenses/by/4.0/", "isAccessibleForFree": true, "creator": { "@type": "Organization", "@id": "https://knowyourprime.com/#organization", "name": "KnowYourPrime", "url": "https://knowyourprime.com" }, "publisher": { "@type": "Organization", "@id": "https://knowyourprime.com/#organization", "name": "KnowYourPrime", "url": "https://knowyourprime.com" }, "keywords": [ "wearable accuracy", "heart rate variability", "sleep tracking", "blood oxygen", "VO2 max", "evidence rating", "validation studies" ], "dateModified": "2026-10-27", "distribution": [ { "@type": "DataDownload", "name": "Evidence Registry index", "encodingFormat": "application/json", "contentUrl": "https://knowyourprime.com/evidence.json" }, { "@type": "DataDownload", "name": "Research Desk claims", "encodingFormat": "application/json", "contentUrl": "https://knowyourprime.com/claims.json" }, { "@type": "DataDownload", "name": "Rating and finding changes", "encodingFormat": "application/json", "contentUrl": "https://knowyourprime.com/rating-changes.json" } ] } ``` ```json {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://knowyourprime.com/"},{"@type":"ListItem","position":2,"name":"Evidence Registry"}]} ```