{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,21]],"date-time":"2026-04-21T13:49:24Z","timestamp":1776779364817,"version":"3.51.2"},"reference-count":18,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2022,4,12]],"date-time":"2022-04-12T00:00:00Z","timestamp":1649721600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003725","name":"National Research Foundation of Korea","doi-asserted-by":"publisher","award":["2022R1A5A7000765"],"award-info":[{"award-number":["2022R1A5A7000765"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003725","name":"National Research Foundation of Korea","doi-asserted-by":"publisher","award":["NRF-2022R1A2C2010298"],"award-info":[{"award-number":["NRF-2022R1A2C2010298"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Glycated hemoglobin (HbA1c) is an important factor in monitoring diabetes. Since the glycated hemoglobin value reflects the average blood glucose level over 3 months, it is not affected by exercise or food intake immediately prior to measurement. Thus, it is used as the most basic measure of evaluating blood-glucose control over a certain period and predicting the occurrence of long-term complications due to diabetes. However, as the existing measurement methods are invasive, there is a burden on the measurement subject who has to endure increased blood gathering and exposure to the risk of secondary infections. To overcome this problem, we propose a machine-learning-based noninvasive estimation method in this study using photoplethysmography (PPG) signals. First, the development of the device used to acquire the PPG signals is described in detail. Thereafter, discriminative and effective features are extracted from the acquired PPG signals using the device, and a machine-learning algorithm is used to estimate the glycated hemoglobin value from the extracted features. Finally, the performance of the proposed method is evaluated by comparison with existing model-based methods.<\/jats:p>","DOI":"10.3390\/s22082963","type":"journal-article","created":{"date-parts":[[2022,4,12]],"date-time":"2022-04-12T22:48:45Z","timestamp":1649803725000},"page":"2963","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":19,"title":["Machine-Learning-Based Noninvasive In Vivo Estimation of HbA1c Using Photoplethysmography Signals"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6784-5591","authenticated-orcid":false,"given":"Tae-Ho","family":"Kwon","sequence":"first","affiliation":[{"name":"School of Electrical Engineering, Kookmin University, Seoul 02707, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5052-3844","authenticated-orcid":false,"given":"Ki-Doo","family":"Kim","sequence":"additional","affiliation":[{"name":"School of Electrical Engineering, Kookmin University, Seoul 02707, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,4,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1349","DOI":"10.2337\/dc07-1707","article-title":"Longitudinal association of glucose metabolism with retinopathy: Results from the Australian Diabetes Obesity and Lifestyle (AusDiab) study","volume":"31","author":"Tapp","year":"2008","journal-title":"Diabetes Care"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"4473","DOI":"10.1039\/c2ra22351a","article-title":"Recent advances in electrochemical glucose biosensors: A review","volume":"3","author":"Chen","year":"2012","journal-title":"RSC Adv."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"363","DOI":"10.1016\/j.tibtech.2014.04.005","article-title":"Non-invasive wearable electrochemical sensors: A review","volume":"32","author":"Bandodkar","year":"2014","journal-title":"Trends Biotechnol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"261","DOI":"10.1016\/j.snb.2013.10.140","article-title":"Electrodeposition of nickel oxide and platinum nanoparticles on electro-chemically reduced graphene oxide film as a nonenzymatic glucose sensor","volume":"192","author":"Li","year":"2014","journal-title":"Sens. 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