{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,19]],"date-time":"2026-09-19T16:04:30Z","timestamp":1789833870885,"version":"4.0.1"},"reference-count":65,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2025,9,12]],"date-time":"2025-09-12T00:00:00Z","timestamp":1757635200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"University of Manchester","award":["10038931"],"award-info":[{"award-number":["10038931"]}]},{"name":"University of Manchester","award":["101057482"],"award-info":[{"award-number":["101057482"]}]},{"name":"UK Research and Innovation (UKRI) under the UK government\u2019s Horizon Europe funding guarantee","award":["10038931"],"award-info":[{"award-number":["10038931"]}]},{"name":"UK Research and Innovation (UKRI) under the UK government\u2019s Horizon Europe funding guarantee","award":["101057482"],"award-info":[{"award-number":["101057482"]}]},{"DOI":"10.13039\/501100000780","name":"European Union","doi-asserted-by":"publisher","award":["10038931"],"award-info":[{"award-number":["10038931"]}],"id":[{"id":"10.13039\/501100000780","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000780","name":"European Union","doi-asserted-by":"publisher","award":["101057482"],"award-info":[{"award-number":["101057482"]}],"id":[{"id":"10.13039\/501100000780","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pathophysiology"],"abstract":"<jats:p>Background: Fatigue has been associated with poorer quality of life and increased morbidity in multiple clinical fields. Patients with autonomic dysfunction have been found to experience poorer physiological health, as well as having an increased risk of comorbidity and all-cause mortality. Heart rate variability (HRV) has been documented as a validated tool to assess autonomic function in clinical practice. The aim of this systematic review was to understand the relationship between fatigue and HRV in different medical populations. Methods: A systematic search was conducted in MEDLINE via Web of Science and Scopus. Results: A total of seventeen articles were identified for inclusion. Patients with Chronic Fatigue Syndrome were the most investigated population (n = 7), followed by cancer (n = 4) and Multiple Sclerosis (n = 4). The most implemented fatigue measure was the Multidimension Fatigue Inventory Scale used in four studies and HRV was monitored by electrocardiogram in nine studies. The most recorded and analysed domain for HRV was the frequency parameters. A significant association between increased subjective fatigue and imbalanced metrics of HRV (p &lt; 0.05) was identified in fourteen articles. However, results from this review were heterogenous partly owing to the inconsistency with the instruments implemented to monitor HRV and measure fatigue. Additionally, only a small number of medical conditions were investigated, and the patients were predominately older adults (mean age 43.2) and women (64%). Conclusions: Despite these discrepancies, the reviewed evidence suggests that a rise in sympathetic activity and reduced parasympathetic tone are associated with an increased perception of fatigue in medical populations.<\/jats:p>","DOI":"10.3390\/pathophysiology32030046","type":"journal-article","created":{"date-parts":[[2025,9,15]],"date-time":"2025-09-15T10:51:33Z","timestamp":1757933493000},"page":"46","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Decreased Heart Rate Variability Is Associated with Increased Fatigue Across Different Medical Populations: A Systematic Review"],"prefix":"10.3390","volume":"32","author":[{"ORCID":"https:\/\/orcid.org\/0009-0009-5401-6992","authenticated-orcid":false,"given":"Sophie Maria","family":"Penfold","sequence":"first","affiliation":[{"name":"School of Health Sciences, Faculty of Biology, Medicine and Health, Division of Informatics, Imaging and Data Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0606-2168","authenticated-orcid":false,"given":"James","family":"Cunningham","sequence":"additional","affiliation":[{"name":"School of Health Sciences, Faculty of Biology, Medicine and Health, Division of Informatics, Imaging and Data Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pauline","family":"Whelan","sequence":"additional","affiliation":[{"name":"School of Health Sciences, Faculty of Biology, Medicine and Health, Division of Informatics, Imaging and Data Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5138-0707","authenticated-orcid":false,"given":"Martin G.","family":"McCabe","sequence":"additional","affiliation":[{"name":"School of Medical Sciences, Faculty of Biology, Medicine and Health, Division of Cancer Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2187-9195","authenticated-orcid":false,"given":"John","family":"Ainsworth","sequence":"additional","affiliation":[{"name":"School of Health Sciences, Faculty of Biology, Medicine and Health, Division of Informatics, Imaging and Data Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,9,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"100266","DOI":"10.1016\/j.bbih.2021.100266","article-title":"Dissecting the fatigue experience: A scoping review of fatigue definitions, dimensions, and measures in non-oncologic medical conditions","volume":"15","author":"Billones","year":"2021","journal-title":"Brain Behav. 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