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Accuracy of heart rate measurement with wrist-worn wearable devices in various skin tones: a systematic review

Open access
Koerber, Daniel, Khan, Shawn, Shamsheri, Tahmina, Kirubarajan, Abirami, Mehta, Sangeeta·2023·Journal of Racial and Ethnic Health Disparities
DOI 10.1007/s40615-022-01446-9PMC PMC9662769
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Abstract

Background Wearable consumer technology allows for the collection of a growing amount of personal health data. Through the analysis of reflected LED light on the skin, heart rate measurement and arrhythmia detection can be performed. Given that melanin alters skin light absorption, this study seeks to summarize the accuracy of cardiac data from wrist-worn wearable devices for participants of varying skin tones. Methods We conducted a systematic review, searching Embase, MEDLINE, CINAHL, and Cochrane for original studies that stratified heart rate and rhythm data for consumer wearable technology according to participant race and/or skin tone. Results A total of 10 studies involving 469 participants met inclusion criteria. The frequency-weighted Fitzpatrick score for skin tone was reported in six studies ( n = 293), with a mean participant score of 3.5 (range 1–6). Overall, four of the ten studies reported a significant reduction in accuracy of heart rate measurement with wearable devices in darker-skinned individuals, compared to participants with lighter skin tones. Four studies noted no effect of user skin tone on accuracy. The remaining two studies showed mixed results. Conclusions Preliminary evidence is inconclusive, but some studies suggest that wearable devices may be less accurate for detecting heart rate in participants with darker skin tones. Higher quality evidence is necessary, with larger sample sizes and more objective stratification of participants by skin tone, in order to characterize potential racial bias in consumer devices.

AI snapshot

Written from the paper’s full text.

TL;DR

This systematic review of 10 observational studies and 469 participants found mixed evidence on whether wrist-worn wearable heart-rate accuracy differs by skin tone. Some studies reported reduced accuracy in darker-skinned individuals, but the authors conclude the evidence is preliminary and inconclusive.

Key findings

  • Of 10 included studies, 4 reported statistically significant reductions in heart-rate accuracy in participants with darker skin tones, 4 found no effect of skin tone, and 2 showed mixed results; no study reported higher accuracy in darker-skinned participants.
  • Six studies reported a frequency-weighted mean Fitzpatrick skin-tone score of 3.5 (range 1–6) across 293 participants.
  • Specific reported effects included lower accuracy in darker skin in Hermand et al. (p < 0.001), Pasadyn et al. (p = 0.01), Hochstadt et al. (linear regression coefficient = 0.98, p < 0.001), and Spierer et al., where Mio Alpha mean average error was 16 bpm in Fitzpatrick 6 vs 3 bpm in Fitzpatrick 1.
  • In all five studies comparing manufacturers, the Apple Watch was found more accurate than other commercial devices; Etiwy et al. reported a correlation coefficient of 0.80 for Apple Watch vs 0.52 for Garmin devices.

Methods

  • Systematic review conducted per PRISMA guidelines, searching Embase, MEDLINE, CINAHL, and Cochrane CENTRAL from database inception to Nov 5, 2021 for original studies stratifying heart-rate or rhythm data from consumer wearables by participant race and/or skin tone.
  • The search yielded 656 articles; after duplicate removal, 581 records remained, 25 full texts were reviewed, 6 met inclusion criteria, and 4 additional studies were found by hand and backwards searching, yielding 10 observational cohort studies with 469 participants (mean age 34 years, range 20–62; 38% women).
  • Data extraction and quality assessment used the RoBANS tool, with findings regarding race outcomes extracted and qualitatively analyzed; heterogeneity precluded meta-analysis.

Limitations

  • The authors state that included studies were not blinded, had small sample sizes, evaluated primarily young subjects, and used different wearable device brands and models.
  • The authors also state that many studies reporting significant skin-tone effects did not quantify the magnitude of error, skin-tone reporting was inconsistent, and heterogeneity precluded meta-analysis; chest straps used as a gold standard in 3 of 10 studies have never been validated across different skin tones.
  • Evident from the text: only 3 of 10 studies included participants with Fitzpatrick 6 skin tones, and none of the included studies compared atrial fibrillation or other arrhythmia detection, or oxygen saturation, across skin tones.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1007/s40615-022-01446-9

Cites

22 of 22 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 48 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    The identified studies in this review included small sample sizes.

    “The identified studies in this review were not blinded, included small sample sizes, evaluated primarily young subjects, and used different wearable device brands and models.”
    Quote in the paperSubstantial claim
  • Findingown data

    The identified studies in this review used different wearable device brands and models.

    “The identified studies in this review were not blinded, included small sample sizes, evaluated primarily young subjects, and used different wearable device brands and models.”
    Quote in the paperSubstantial claim
  • Findingcitation

    Hermand et al. reported lower heart rate accuracy in patients with darker skin (p < 0.001).

    “Hermand et al. reported lower heart rate accuracy in patients with darker skin (p < 0.001) [15].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [15] Hermand E, Cassirame J, Ennequin G, Hue O. Validation of a photoplethysmographic heart rate monitor: polar OH1. Int J Sport Med [Internet]. 2019/06/13. 2019;40:462–7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/31189190 source

      Not checked in the free run.

  • Findingcitation

    As a gold standard comparison for accuracy, either an ECG (n = 7) or a chest strap (n = 3) was used.

    “As a gold standard comparison for accuracy, either an ECG (n = 7) or a chest strap (n = 3) was used, two modalities that are known to correlate well [13].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13] Schaffarczyk M, Rogers B, Reer R, Gronwald T. Validity of the polar H10 sensor for heart rate variability analysis during resting state and incremental exercise in recreational men and women. Sensors. 2022;22:6536. source

      Not checked in the free run.

  • Findingcitation

    In three of the included studies, skin tone was the primary variable considered in the accuracy of wrist-worn heart rate monitors.

    “In three of the included studies, skin tone was the primary variable considered in the accuracy of wrist-worn heart rate monitors [1, 2, 14].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [1] Sañudo B, De Hoyo M, Muñoz-López A, Perry J, Abt G. Pilot study assessing the influence of skin type on the heart rate measurements obtained by photoplethysmography with the Apple Watch. J Med Syst. 2019;43. source

      Not checked in the free run.

    • cites [2] Bent B, Goldstein BA, Kibbe WA, Dunn JP. Investigating sources of inaccuracy in wearable optical heart rate sensors. NPJ Digit Med [Internet]. 2020/02/13. 2020;3:18. Available from: https://www.ncbi.nlm.nih.gov/pubmed/32047863 source

      Not checked in the free run.

    • cites [14] Ray I, Liaqat D, Gabel M, E. de L. Skin tone, confidence, and data quality of heart rate sensing in WearOS smartwatches. IEEE Int Conf Pervasive Comput Commun Work other Affil Events. 2021;213–9. source

      Not checked in the free run.

  • Classified as probably not a substantial claim. 17
  • May combine two claims. 19

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Of the ten included studies, five compared the relative accuracy of different manufacturers.

    “Of the ten studies, five compared the relative accuracy of different manufacturers.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    Etiwy et al. found the Apple Watch to follow ECG data with a correlation coefficient of 0.80, compared to 0.52 in Garmin devices.

    “For instance, Etiwy et al. found the Apple Watch to follow ECG data with a correlation coefficient of 0.80, compared to 0.52 in Garmin devices [9].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [9] Etiwy M, Akhrass Z, Gillinov L, Alashi A, Wang R, Blackburn G, et al. Accuracy of wearable heart rate monitors in cardiac rehabilitation. Cardiovasc Diagn Ther [Internet]. 2019/07/06. 2019;9:262–71. Available from: https://www.ncbi.nlm.nih.gov/pubmed/31275816 source

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    The review identified a relative scarcity of studies considering skin tone interactions in smart watch cardiac accuracy, resulting in inconclusive findings.

    “This review identified a relative scarcity of studies that consider the interactions of skin tone when characterizing smart watch device accuracy in cardiac outcomes, resulting in inconclusive findings.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    In the seven other included studies, skin tone was one of several covariates considered in the accuracy analysis.

    “For the seven other studies, skin tone was one of several covariates considered in the accuracy analysis.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The systematic review included 10 studies involving 469 participants.

    “A total of 10 studies involving 469 participants met inclusion criteria.”
    • Also stated in: § Results · plain
      “The 10 studies included a total of 469 participants, with a mean age of 34 years (range 20–62); a total of 38% (range 0–67%) of participants were women.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    The Fitzpatrick scale was used to classify participant skin tones in eight of the ten included studies.

    “The Fitzpatrick scale was used to classify participant skin tones in eight of the ten studies.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    None of the included studies assessed oxygen saturation or other vital signs.

    “Similarly, none of the studies assessed oxygen saturation or other vital signs.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data

    The most common wearable device brands studied were Apple Watch (n = 6), Fitbit (n = 5), Mio Alpha (n = 3), and Garmin (n = 3).

    “The most common wearable device brands that were studied included the Apple Watch (n = 6), Fitbit (n = 5), Mio Alpha (n = 3), and Garmin (n = 3).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In the two studies that did not use the Fitzpatrick scale, one classified participants as white, Black, or other, and another classified participants by ethnic background including Asian, Black, and Hispanic, precluding aggregate analysis of skin tone outcomes.

    “In the two studies that did not use the Fitzpatrick scale, one classified participants as white, Black, or other, and another classified participants based on ethnic background, including Asian, Black, and Hispanic — precluding aggregate analysis of skin tone outcomes.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    Wallen et al. noted lower heart rate accuracy in participants with a Fitzpatrick scale score > 4 with the Apple Watch, but not in the other studied smartwatches.

    “Wallen et al. noted lower heart rate accuracy in participants with a Fitzpatrick scale score > 4 with the Apple Watch, but not in the other studied smartwatches [12].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [12] Wallen MP, Gomersall SR, Keating SE, Wisloff U, Coombes JS. Accuracy of heart rate watches: implications for weight management. PLoS One [Internet]. 2016/05/28. 2016;11:e0154420. Available from: https://www.ncbi.nlm.nih.gov/pubmed/27232714 source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Ray et al. found that various WearOS watches systematically underestimate the reliability of HR readings taken from dark skin, despite no substantial differences in error, leading to significantly fewer recorded data points in patients with dark skin.

    “Ray et al. found that various WearOS watches systematically underestimate the reliability of HR readings taken from dark skin, despite no substantial differences in error, leading to significantly fewer recorded data points in patients with dark skin [14].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [14] Ray I, Liaqat D, Gabel M, E. de L. Skin tone, confidence, and data quality of heart rate sensing in WearOS smartwatches. IEEE Int Conf Pervasive Comput Commun Work other Affil Events. 2021;213–9. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Shcherbina et al. noted that smart watch device error was higher for darker skin tones, but the degree of this effect was not reported.

    “Shcherbina et al. noted that smart watch device error was higher for darker skin tones, but the degree of this effect was not reported [11].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [11] Shcherbina A, Mattsson CM, Waggott D, Salisbury H, Christle JW, Hastie T, et al. Accuracy in wrist-worn, sensor-based measurements of heart rate and energy expenditure in a diverse cohort. J Pers Med [Internet]. 2017/05/26. 2017;7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/28538708 source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Etiwy et al. and Sanudo et al. found that skin color did not influence heart rate accuracy.

    “Etiwy et al. and Sanudo et al. similarly found that skin color did not influence heart rate accuracy [1, 9].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [1] Sañudo B, De Hoyo M, Muñoz-López A, Perry J, Abt G. Pilot study assessing the influence of skin type on the heart rate measurements obtained by photoplethysmography with the Apple Watch. J Med Syst. 2019;43. source

      Not checked in the free run.

    • cites [9] Etiwy M, Akhrass Z, Gillinov L, Alashi A, Wang R, Blackburn G, et al. Accuracy of wearable heart rate monitors in cardiac rehabilitation. Cardiovasc Diagn Ther [Internet]. 2019/07/06. 2019;9:262–71. Available from: https://www.ncbi.nlm.nih.gov/pubmed/31275816 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Heterogeneity across included studies precluded meta-analysis and may contribute to variability in reported results.

    “This heterogeneity precluded meta-analysis and may contribute to the variability in reported results.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    ECG and chest strap are two modalities that are known to correlate well.

    “As a gold standard comparison for accuracy, either an ECG (n = 7) or a chest strap (n = 3) was used, two modalities that are known to correlate well [13].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [13] Schaffarczyk M, Rogers B, Reer R, Gronwald T. Validity of the polar H10 sensor for heart rate variability analysis during resting state and incremental exercise in recreational men and women. Sensors. 2022;22:6536. source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    The evidence is inconclusive, but some studies suggest that wearable devices may be less accurate for detecting heart rate in participants with darker skin tones.

    “Preliminary evidence is inconclusive, but some studies suggest that wearable devices may be less accurate for detecting heart rate in participants with darker skin tones.”
    • Also stated in: § Discussion · hedged
      “However, the included studies described mixed results and as such, it remains unclear whether wearable devices have reduced accuracy in heart rate and arrhythmia detection in people with darker skin tones.”
    • Also stated in: § Conclusion · boosted
      “Early evidence of racial bias in wrist-worn wearables is mixed, but some studies demonstrate reduced accuracy of heart rate data in users with darker skin tones.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    No exclusions were applied on the basis of language or country of origin.

    “No exclusions were applied on the basis of language or country of origin.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    The study used rigorous research methodology including the search of multiple research databases and screening of publications by two independent reviewers in duplicate.

    “The study used rigorous research methodology including the search of multiple research databases and screening of publications by two independent reviewers in duplicate.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    Title and abstract screening, full-text review, and data extraction were performed independently by two investigators, with a third reviewer resolving discrepancies.

    “Title and abstract screening, full-text review, and data extraction were performed independently by two investigators (SK and DK), with a third reviewer (AK) resolving discrepancies.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Modern wearable devices rely on two components: photoplethysmography (PPG) and electrical sensors.

    “The associated hardware in modern devices relies on two components: photoplethysmography (PPG), which passively monitors heart rate and rhythm, and electrical sensors, which require the user to remain still and touch the device with their opposite hand throughout the detection period [1].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [1] Sañudo B, De Hoyo M, Muñoz-López A, Perry J, Abt G. Pilot study assessing the influence of skin type on the heart rate measurements obtained by photoplethysmography with the Apple Watch. J Med Syst. 2019;43. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Pulse oximeters measure LED light that shines through the tissue to the opposite side, restricting them to locations that can be transilluminated, such as the earlobes and fingers.

    “Instead of photodetectors measuring reflected light, they measure LED light that shines through the tissue to the opposite side, restricting it to locations that can be transilluminated, such as the earlobes and fingers [5].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [5] Khan Y, Han D, Pierre A, Ting J, Wang X, Lochner CM, et al. A flexible organic reflectance oximeter array. Proc Natl Acad Sci U S A. 2018;115:E11015–24. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    The Risk of Bias Assessment Tool for Nonrandomized Studies (RoBANS) was used to assess methodological quality of included studies, appraised independently by two reviewers.

    “The Risk of Bias Assessment Tool for Nonrandomized Studies (RoBANS) tool was used to assess the methodological quality of included studies. Studies were appraised independently by two parallel reviewers (SK, DK).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The authors systematically searched four databases from database inception to Nov 5, 2021.

    “The authors systematically searched four databases from database inception to Nov 5, 2021: (1) the Ovid versions of MEDLINE and MEDLINE Daily including e-publications, in progress, and non-indexed citations; (2) Embase Classic and Embase; (3) CINAHL; and (4) Cochrane CENTRAL.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The review was conducted according to PRISMA guidelines.

    “This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    Darker skin tone reduced accuracy in the Hochstadt et al. comparison, albeit with a relatively small impact.

    “Hochstadt et al. noted a linear regression coefficient of 0.98 (p < 0.001) when comparing PPG to ECG data in patients with darker skin (Fitzpatrick 5 or 6), suggesting that darker skin tone reduced accuracy, albeit with a relatively small impact [3].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [3] Hochstadt A, Havakuk O, Chorin E, Schwartz AL, Merdler I, Laufer M, et al. Continuous heart rhythm monitoring using mobile photoplethysmography in ambulatory patients. J Electrocardiol [Internet]. 2020/05/04. 2020;60:138–41. Available from: https://www.ncbi.nlm.nih.gov/pubmed/32361522 source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisereasoning

    It remains unclear whether the inaccuracy of transmission PPG in darker skin tones holds true for the reflectance PPG used in consumer wrist-worn devices.

    “While the inaccuracy of transmission PPG used in pulse oximeters is well established in darker skin tones, it remains unclear whether this holds true for the reflectance PPG used in consumer wrist-worn devices.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Hemoglobin in dermal blood vessels drives the bulk of light absorption, and changes in blood pressure and flow rate affect light absorption, which is detected by PPG optical sensors.

    “Hemoglobin in dermal blood vessels drives the bulk of light absorption, and thus changes in blood pressure and flow rate affect light absorption, which is then detected by PPG optical sensors [2, 3].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [2] Bent B, Goldstein BA, Kibbe WA, Dunn JP. Investigating sources of inaccuracy in wearable optical heart rate sensors. NPJ Digit Med [Internet]. 2020/02/13. 2020;3:18. Available from: https://www.ncbi.nlm.nih.gov/pubmed/32047863 source

      Not checked in the free run.

    • cites [3] Hochstadt A, Havakuk O, Chorin E, Schwartz AL, Merdler I, Laufer M, et al. Continuous heart rhythm monitoring using mobile photoplethysmography in ambulatory patients. J Electrocardiol [Internet]. 2020/05/04. 2020;60:138–41. Available from: https://www.ncbi.nlm.nih.gov/pubmed/32361522 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Backwards searching was performed by screening the reference lists of all included studies to identify relevant articles.

    “Backwards searching was also performed by screening the reference lists of all included studies to identify relevant articles.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    PPG relies on LEDs projecting light onto the skin and photodetectors measuring the quantity of reflected light.

    “This technology relies on LEDs projecting light onto the skin, and photodetectors measuring the quantity of reflected light [1, 2].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [1] Sañudo B, De Hoyo M, Muñoz-López A, Perry J, Abt G. Pilot study assessing the influence of skin type on the heart rate measurements obtained by photoplethysmography with the Apple Watch. J Med Syst. 2019;43. source

      Not checked in the free run.

    • cites [2] Bent B, Goldstein BA, Kibbe WA, Dunn JP. Investigating sources of inaccuracy in wearable optical heart rate sensors. NPJ Digit Med [Internet]. 2020/02/13. 2020;3:18. Available from: https://www.ncbi.nlm.nih.gov/pubmed/32047863 source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    There are limitations to this systematic review, largely related to the preliminary nature of the evidence base.

    “There are limitations to this systematic review, largely related to the preliminary nature of the evidence base.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    A retrospective study of 7126 patients with COVID-19 found that pulse oximetry overestimated arterial oxygen saturation among Asian, Black, and Hispanic patients compared to white patients, leading to a delay in guideline-based therapies.

    “Similarly, a retrospective study of 7126 patients with COVID-19 found that pulse oximetry overestimated arterial oxygen saturation among Asian, Black, and Hispanic patients compared to white patients, leading to a delay in the initiation of guideline-based therapies [7].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [7] Fawzy A, Wu TD, Wang K, Robinson ML, Farha J, Bradke A, et al. Racial and ethnic discrepancy in pulse oximetry and delayed identification of treatment eligibility among patients with COVID-19. JAMA Intern Med. 2022;21224. source

      Not checked in the free run.

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  • The paper relies on this without support.

    Melanin is the main absorbent of light in the epidermis.

    “Given that melanin is the main absorbent of light in the epidermis, it is theorized that this might similarly interfere with the PPG signal estimation process.”

  • The paper relies on this without support.

    Chest straps have never been validated across different skin tones.

    “Further, despite being used as a gold standard in three of the ten included studies, chest straps have never been validated across different skin tones.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Melanin absorption of green light is a primary factor interfering with optical signal detection in PPG-based measurements.

    “In PPG-based measurements, melanin absorption of green light was identified as a primary factor interfering with optical signal detection [9].”

    From Photoplethysmography in Diverse Skin Tones: Evaluating Bias in Smartwatch Health Monitoring (2025) · cites this paper as [9]

    The Introduction says melanin absorbs light in the epidermis and is theorized to interfere with PPG signal estimation. It does not identify absorption of green light as a primary interfering factor. The Discussion instead reports that green wavelengths showed greater heart-rate measurement accuracy across skin types than other wavelengths. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Apple devices tended to perform better during exercise but still slightly underestimated peak values, a discrepancy deemed clinically negligible.

    “By contrast, Apple devices tended to perform better during exercise but still slightly underestimated peak values, a discrepancy deemed clinically negligible [9].”

    From Photoplethysmography in Diverse Skin Tones: Evaluating Bias in Smartwatch Health Monitoring (2025) · cites this paper as [9]

    The Results (page not available in our copy) report that all five studies comparing manufacturers found the Apple Watch more accurate than other commercial devices. The review does not say that this advantage was specific to exercise, or that Apple devices slightly underestimated peak heart rates or that such a discrepancy was clinically negligible. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • No single brand was consistently superior across all skin tones and activities.

    “Koerber et al. (2023), in a systematic review, emphasized this heterogeneity, concluding that no single brand was consistently superior across all skin tones and activities [9].”

    From Photoplethysmography in Diverse Skin Tones: Evaluating Bias in Smartwatch Health Monitoring (2025) · cites this paper as [9]

    The Results (page unavailable) report mixed findings across skin tones and some differences between devices, supporting the claim of heterogeneity. But they also say that all five studies comparing manufacturers found the Apple Watch more accurate than the other devices; the review does not establish a brand ranking across all skin tones and activities. (LLM, conf=0.84)

    Experimental — accuracy not yet measured

  • Apple and Fitbit's proprietary algorithms outperform smaller-brand or open-source counterparts, largely because of superior noise filtering and adaptive calibration.

    “Comparative evaluations indicate that Apple and Fitbit’s proprietary algorithms outperform smaller-brand or open-source counterparts, largely because of superior noise filtering and adaptive calibration [9,11].”

    From Photoplethysmography in Diverse Skin Tones: Evaluating Bias in Smartwatch Health Monitoring (2025) · cites this paper as [9]

    The Results (page not available in our copy) report that all five studies comparing manufacturers found the Apple Watch more accurate than other commercial devices. The Introduction says proprietary algorithms convert optical measurements into heart-rate data, but the paper does not establish that Fitbit also outperforms other brands, compare either brand with open-source algorithms, or attribute an advantage to noise filtering or adaptive calibration. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Errors during exercise monitoring may result in inappropriate training intensities or misleading recovery assessments.

    “Errors during exercise monitoring may result in inappropriate training intensities or misleading recovery assessments [7,8,9].”

    From Photoplethysmography in Diverse Skin Tones: Evaluating Bias in Smartwatch Health Monitoring (2025) · cites this paper as [9]

    The Results (page unavailable) report heart-rate measurement errors in some wrist-worn devices, which supports the premise that exercise-monitoring readings can be inaccurate. The paper does not address whether those errors lead to inappropriate training intensities or misleading recovery assessments. (LLM, conf=0.79)

    Experimental — accuracy not yet measured

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Spierer results describe skin types the table says were absent

    Major

    Table 1 says the Spierer study had no Fitzpatrick 1 or 6 participants, but the Results section compares measurement errors in Fitzpatrick 1 and 6 patients from that study.

  • Hochstadt study year differs between table and reference

    Minor

    Table 1 labels the Hochstadt study as 2021, while its reference gives a 2020 publication year.

  • Wallen study year differs between table and reference

    Minor

    Table 1 labels the Wallen study as 2015, while its reference gives a 2016 publication year.

3 of 3

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Authors
Koerber, D., Khan, S., Shamsheri, T., Kirubarajan, A., & Mehta, S.
Affiliations
  • University of Toronto (CA)
  • McMaster University (CA)
  • Mount Sinai Hospital (CA)
Corresponding author
Mehta, Sangeeta
ORCID
Venue
Journal of Racial and Ethnic Health Disparities
Publisher
Springer Science and Business Media LLC
Published
2022-11-14
Volume
10
Issue
6
Pages
2676-2684
ISSN
  • 2196-8837 (ISSN-L)
  • 2197-3792
DOI
10.1007/s40615-022-01446-9
PMC
PMC9662769
OpenAlex
W4308963722
Semantic Scholar
1c5e53690208ac097e5604fd23564e3cf10dfb99
Cited by
91
References
22
Citations by year
2026: 26 · 2025: 37 · 2024: 21 · 2023: 7
FWCI
1.45
Type
journal article
Language
en
Open access
Licence
Locations
  • Journal of Racial and Ethnic Health Disparities (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Physical Sciences › Engineering › Biomedical Engineering › Non-Invasive Vital Sign Monitoring
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › ECG Monitoring and Analysis
  • Health Sciences › Health Professions › General Health Professions › Mobile Health and mHealth Applications
Keywords
heart rate measurement, wearable devices, skin tone, Fitzpatrick skin type, melanin, racial bias, consumer health technology, arrhythmia detection, accuracy
MeSH terms
Wearable Electronic Devices, Heart Rate, Humans, Skin Pigmentation, Wrist

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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