{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,24]],"date-time":"2026-06-24T23:18:23Z","timestamp":1782343103101,"version":"3.54.5"},"reference-count":64,"publisher":"Public Library of Science (PLoS)","issue":"12","license":[{"start":{"date-parts":[[2023,12,11]],"date-time":"2023-12-11T00:00:00Z","timestamp":1702252800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS ONE"],"abstract":"<jats:p>Debilitating symptoms of fatigue and accompanying \u201cbrain fog\u201d are observed among patients with various chronic health conditions. Unfortunately, an efficient and psychometrically sound instrument to assess these co-occurring symptoms is unavailable. Here, we report the development and initial psychometric properties of the Fatigue and Altered Cognition Scale (the FACs), a measure of self-reported central fatigue and brain fog. Traumatic brain injury (TBI) was chosen to model and develop the FACs due to research team expertise and established links between TBI and the symptom complex. Potential items were generated by researchers and clinicians with experience treating these symptoms, drawing from relevant literature and review of patient responses to measures from past and current TBI studies. The 20 candidate items for the FACs\u2014ten each to assess altered cognition (i.e., brain fog) and central fatigue\u2013were formatted on an electronic visual analogue response scale (eVAS) via an online survey. Demographic information and history of TBI were obtained. A total of 519 participants consented and provided usable data (average age = 40.23 years; 73% female), 204 of whom self-reported a history of TBI (75% reported mild TBI). Internal consistency and reliability values were calculated. Confirmatory factor analysis (CFA) examined the presumed two-factor structure of the FACs and a one-factor solution for comparison. A measurement invariance test of the two latent constructs (altered cognition, fatigue) among participants with and without TBI was conducted. All items demonstrated normal distribution. Cronbach\u2019s alpha coefficients indicated good internal consistency for both factors (\u03b1\u2019s = .95). Omega reliability values were favorable (\u03b1\u2019s = .95). CFA supported the presumed two-factor model and item loadings which outperformed the one-factor model. Measurement invariance found the two-factor structure was consistent between the two groups. Implications of these findings, study limitations, and potential use of the FACs in clinical research and practice are discussed.<\/jats:p>","DOI":"10.1371\/journal.pone.0295593","type":"journal-article","created":{"date-parts":[[2023,12,11]],"date-time":"2023-12-11T18:28:15Z","timestamp":1702319295000},"page":"e0295593","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":13,"title":["Efficient assessment of brain fog and fatigue: Development of the Fatigue and Altered Cognition Scale (FACs)"],"prefix":"10.1371","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6608-7714","authenticated-orcid":true,"given":"Timothy R.","family":"Elliott","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yu-Yu","family":"Hsiao","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kathleen","family":"Randolph","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Randall J.","family":"Urban","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Melinda","family":"Sheffield-Moore","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Richard B.","family":"Pyles","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Brent E.","family":"Masel","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tamara","family":"Wexler","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7020-930X","authenticated-orcid":true,"given":"Traver J.","family":"Wright","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2023,12,11]]},"reference":[{"key":"pone.0295593.ref001","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1089\/act.2020.29313.klu","article-title":"Brain fog\u201d: Exploring a symptom commonly encountered in clinical practice","volume":"27","author":"K. Lucius","year":"2021","journal-title":"Focus Altern Complement Ther"},{"key":"pone.0295593.ref002","article-title":"A treatable syndrome in patients with traumatic brain injury","author":"RJ Urban","year":"2020","journal-title":"J Neurotrauma"},{"key":"pone.0295593.ref003","doi-asserted-by":"crossref","first-page":"937","DOI":"10.1089\/neu.2010.1516","article-title":"Long-term outcomes after uncomplicated mild traumatic brain injury: a comparison with trauma controls","volume":"28","author":"J Ponsford","year":"2011","journal-title":"J Neurotrauma"},{"key":"pone.0295593.ref004","first-page":"63","article-title":"Caught in the thickness of brain fog: exploring the cognitive symptoms of chronic fatigue syndrome","volume":"4","author":"AJ Ocon","year":"2013","journal-title":"Front Physiol"},{"key":"pone.0295593.ref005","doi-asserted-by":"crossref","first-page":"25","DOI":"10.2147\/PROM.S179310","article-title":"Psychometric evaluation of the hypoparathyroidism symptom diary.","volume":"10","author":"T Coles","year":"2019","journal-title":"Patient Relat Outcome Meas"},{"key":"pone.0295593.ref006","doi-asserted-by":"crossref","first-page":"565","DOI":"10.1111\/apt.12852","article-title":"Editorial: \u201cbrain fog\u201d and coeliac disease\u2014evidence for its existence.","volume":"40","author":"B Lebwohl","year":"2014","journal-title":"Aliment Pharmacol Ther"},{"key":"pone.0295593.ref007","doi-asserted-by":"crossref","first-page":"549","DOI":"10.1002\/joa3.12325","article-title":"Brain fog in postural tachycardia syndrome: An objective cerebral blood flow and neurocognitive analysis","volume":"36","author":"R Wells","year":"2020","journal-title":"J Arrhythm"},{"key":"pone.0295593.ref008","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1097\/01.rhu.0000120895.20623.9f","article-title":"The prevalence and clinical impact of reported cognitive difficulties (fibrofog) in patients with rheumatic disease with and without fibromyalgia.","volume":"10","author":"RS Katz","year":"2004","journal-title":"J Clin Rheumatol"},{"key":"pone.0295593.ref009","doi-asserted-by":"crossref","first-page":"1918","DOI":"10.1001\/jama.2023.8961","article-title":"Disentangling the postacute sequelae of SARS-CoV-2: E unibus pluram (from one, many).","volume":"329","author":"R Gross","year":"2023","journal-title":"JAMA"},{"key":"pone.0295593.ref010","doi-asserted-by":"crossref","first-page":"1934","DOI":"10.1001\/jama.2023.8823","article-title":"Development of a definition of postacute sequelae of SARS-CoV-2 infection","volume":"329","author":"T Thaweethai","year":"2023","journal-title":"JAMA"},{"key":"pone.0295593.ref011","doi-asserted-by":"crossref","first-page":"395","DOI":"10.1515\/jom-2022-0217","article-title":"Osteopathic manipulative treatment for concussions and postconcussive syndrome in athletes: a literature review.","volume":"123","author":"KD Thomas","year":"2023","journal-title":"J Osteopath Med"},{"key":"pone.0295593.ref012","doi-asserted-by":"crossref","first-page":"136","DOI":"10.1002\/nur.22280","article-title":"Severity and correlates of brain fog in people with traumatic brain injury","volume":"46","author":"T Bell","year":"2023","journal-title":"Res Nurs Health"},{"key":"pone.0295593.ref013","doi-asserted-by":"crossref","first-page":"933","DOI":"10.1682\/JRRD.2013.10.0226","article-title":"Subjective cognitive complaints and neuropsychological test performance following military-related traumatic brain injury","volume":"51","author":"LM French","year":"2014","journal-title":"J Rehabil Res Dev"},{"key":"pone.0295593.ref014","doi-asserted-by":"crossref","first-page":"894758","DOI":"10.3389\/fnhum.2022.894758","article-title":"Use of novel concussion protocol with infralow frequency neuromodulation demonstrates significant treatment response in patients with persistent postconcussion symptoms, a retrospective study.","volume":"16","author":"SB Legarda","year":"2022","journal-title":"Front Hum Neurosci"},{"key":"pone.0295593.ref015","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1080\/09687599.2022.2150600","article-title":"Living \u2018with TBI\u2019 as complex embodiment.","author":"A Duncan","year":"2022","journal-title":"Disabil Soc."},{"key":"pone.0295593.ref016","doi-asserted-by":"crossref","first-page":"581","DOI":"10.1016\/j.mpmed.2023.05.009","article-title":"Persistent symptoms after a mild traumatic brain injury: Assessment and management","volume":"51","author":"PO Jenkins","year":"2023","journal-title":"Medicine"},{"key":"pone.0295593.ref017","doi-asserted-by":"crossref","first-page":"389","DOI":"10.3109\/02699052.2014.884242","article-title":"Neuropsychological and physiological correlates of fatigue following traumatic brain injury","volume":"28","author":"DJ Zgaljardic","year":"2014","journal-title":"Brain Inj"},{"key":"pone.0295593.ref018","doi-asserted-by":"crossref","first-page":"305","DOI":"10.1007\/s10286-013-0212-z","article-title":"What is brain fog? An evaluation of the symptom in postural tachycardia syndrome","volume":"23","author":"AJ Ross","year":"2013","journal-title":"Clin Auton Res."},{"key":"pone.0295593.ref019","doi-asserted-by":"crossref","first-page":"729","DOI":"10.1093\/arclin\/acac004","article-title":"Neurocognitive profiles in patients with persisting cognitive symptoms sssociated with COVID-19.","volume":"37","author":"K Krishnan","year":"2022","journal-title":"Arch Clin Neuropsychol"},{"key":"pone.0295593.ref020","year":"2023","journal-title":"Concussion Signs and Symptoms."},{"key":"pone.0295593.ref021","article-title":"Altered fecal microbiome years after traumatic brain injury","author":"RJ Urban","year":"2020","journal-title":"J Neurotrauma"},{"key":"pone.0295593.ref022","article-title":"Growth hormone alters brain morphometry, connectivity, and behavior in subjects with fatigue after mild traumatic brain injury.","author":"T Wright","year":"2020","journal-title":"J Neurotrauma."},{"key":"pone.0295593.ref023","article-title":"Alterations of the GH\/IGF-I axis and gut microbiome after traumatic brain injury: A new clinical syndrome?","volume":"105","author":"KCJ Yuen","year":"2020","journal-title":"J Clin Endocrinol Metab"},{"key":"pone.0295593.ref024","doi-asserted-by":"crossref","first-page":"305","DOI":"10.1210\/er.2014-1065","article-title":"Pituitary dysfunction after traumatic brain injury: a clinical and pathophysiological approach","volume":"36","author":"F Tanriverdi","year":"2015","journal-title":"Endocr Rev"},{"key":"pone.0295593.ref025","doi-asserted-by":"crossref","first-page":"1565","DOI":"10.1089\/neu.2009.1253","article-title":"Effect of growth hormone replacement therapy on cognition after traumatic brain injury","volume":"27","author":"WM High","year":"2010","journal-title":"J Neurotrauma"},{"key":"pone.0295593.ref026","doi-asserted-by":"crossref","first-page":"845","DOI":"10.1089\/neu.2016.4552","article-title":"Functional changes after recombinant human growth hormone replacement in patients with chronic traumatic brain injury and abnormal growth hormone secretion","volume":"34","author":"KA Mossberg","year":"2017","journal-title":"J Neurotrauma"},{"key":"pone.0295593.ref027","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1146\/annurev-clinpsy-081219-115343","article-title":"Developing and validating clinical questionnaires.","volume":"17","author":"AJ Rosellini","year":"2021","journal-title":"Annu Rev Clin Psychol"},{"key":"pone.0295593.ref028","doi-asserted-by":"crossref","first-page":"318","DOI":"10.1097\/01.HTR.0000300227.67748.77","article-title":"Initial reliability and validity of the Ohio State University TBI Identification method.","volume":"22","author":"JD Corrigan","year":"2007","journal-title":"J Head Trauma Rehabil"},{"key":"pone.0295593.ref029","volume-title":"Report to Congress on Mild Traumatic Brain Injury in the United States: Steps to Prevent a Serious Public Health Problem.","author":"National Center for Injury Prevention and Control (U.S.).","year":"2003"},{"key":"pone.0295593.ref030","author":"NINDS Common Data Elements","journal-title":"In: National Institute of Neurological Disorders and Stroke [Internet]."},{"key":"pone.0295593.ref031","doi-asserted-by":"crossref","first-page":"1811","DOI":"10.1016\/j.apmr.2018.03.023","article-title":"Feasibility and preliminary validation of an online version of the Ohio State University Traumatic Brain Injury Identification method","volume":"99","author":"AH Lequerica","year":"2018","journal-title":"Arch Phys Med Rehabil"},{"key":"pone.0295593.ref032","doi-asserted-by":"crossref","first-page":"217","DOI":"10.1016\/0304-3959(94)90097-3","article-title":"A comparison of pain measurement characteristics of mechanical visual analogue and simple numerical rating scales","volume":"56","author":"DD Price","year":"1994","journal-title":"Pain"},{"key":"pone.0295593.ref033","doi-asserted-by":"crossref","first-page":"800","DOI":"10.2340\/16501977-1031","article-title":"How should we use the visual analogue scale (VAS) in rehabilitation outcomes? II: Visual analogue scales as ratio scales: an alternative to the view of Kersten et al.","volume":"44","author":"DD Price","year":"2012","journal-title":"J Rehabil Med"},{"key":"pone.0295593.ref034","doi-asserted-by":"crossref","first-page":"394","DOI":"10.1007\/s43441-022-00376-2","article-title":"Measurement comparability of electronic and paper administration of visual analogue scales: A review of published studies.","volume":"56","author":"B Byrom","year":"2022","journal-title":"Ther Innov Regul Sci"},{"key":"pone.0295593.ref035","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1007\/BF02310555","article-title":"Coefficient alpha and the internal structure of tests","volume":"16","author":"LJ Cronbach","year":"1951","journal-title":"Psychometrika"},{"key":"pone.0295593.ref036","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1177\/01466216970212006","article-title":"Estimation of composite reliability for congeneric measures","volume":"21","author":"T. Raykov","year":"1997","journal-title":"Appl Psychol Meas"},{"key":"pone.0295593.ref037","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1207\/S15327906MBR3701_04","article-title":"Analytic estimation of standard error and confidence interval for scale reliability","volume":"37","author":"T. Raykov","year":"2002","journal-title":"Multivariate Behav Res"},{"key":"pone.0295593.ref038","doi-asserted-by":"crossref","first-page":"1428","DOI":"10.1037\/pas0000623","article-title":"Factor analysis in psychological assessment research: Common pitfalls and recommendations.","volume":"31","author":"M Sellbom","year":"2019","journal-title":"Psychol Assess"},{"key":"pone.0295593.ref039","doi-asserted-by":"crossref","first-page":"1047","DOI":"10.1080\/09602011.2017.1292921","article-title":"Assessment and treatment of mental fatigue after a traumatic brain injury","volume":"27","author":"B Johansson","year":"2017","journal-title":"Neuropsychol Rehabil"},{"key":"pone.0295593.ref040","doi-asserted-by":"crossref","first-page":"e01056","DOI":"10.1002\/brb3.1056","article-title":"Mental fatigue and impaired cognitive function after an acquired brain injury","volume":"8","author":"A Jonasson","year":"2018","journal-title":"Brain Behav"},{"key":"pone.0295593.ref041","doi-asserted-by":"crossref","first-page":"230","DOI":"10.1177\/0049124192021002005","article-title":"Alternative ways of assessing model fit.","volume":"21","author":"MW Browne","year":"1992","journal-title":"Sociol Methods Res."},{"key":"pone.0295593.ref042","doi-asserted-by":"crossref","first-page":"130","DOI":"10.1037\/1082-989X.1.2.130","article-title":"Power analysis and determination of sample size for covariance structure modeling","volume":"1","author":"RC MacCallum","year":"1996","journal-title":"Psychol Methods"},{"key":"pone.0295593.ref043","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1080\/10705519909540118","article-title":"Cutoff criteria for fit indexes in covariance structure analysis: Conventional criteria versus new alternatives","volume":"6","author":"L Hu","year":"1999","journal-title":"Struct Equ Modeling"},{"key":"pone.0295593.ref044","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1037\/1082-989X.7.1.64","article-title":"Principles and practice in reporting structural equation analyses.","volume":"7","author":"RP McDonald","year":"2002","journal-title":"Psychol Methods."},{"key":"pone.0295593.ref045","doi-asserted-by":"crossref","first-page":"111","DOI":"10.1037\/a0019625","article-title":"Testing model nesting and equivalence.","volume":"15","author":"PM Bentler","year":"2010","journal-title":"Psychol Methods"},{"key":"pone.0295593.ref046","doi-asserted-by":"crossref","first-page":"525","DOI":"10.1007\/BF02294825","article-title":"Measurement invariance, factor analysis and factorial invariance","volume":"58","author":"W. Meredith","year":"1993","journal-title":"Psychometrika"},{"key":"pone.0295593.ref047","doi-asserted-by":"crossref","DOI":"10.4324\/9780203821961","volume-title":"Statistical approaches to measurement invariance","author":"RE Millsap","year":"2012"},{"key":"pone.0295593.ref048","volume-title":"Confirmatory factor analysis for applied research, Second Edition.","author":"TA Brown","year":"2015"},{"key":"pone.0295593.ref049","doi-asserted-by":"crossref","first-page":"471","DOI":"10.1207\/s15328007sem1203_7","article-title":"Teacher\u2019s corner: Testing measurement invariance of second-order factor models.","volume":"12","author":"FF Chen","year":"2005","journal-title":"Struct Equ Modeling"},{"key":"pone.0295593.ref050","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1037\/1082-989X.9.1.93","article-title":"Evaluating the impact of partial factorial invariance on selection in two populations.","volume":"9","author":"RE Millsap","year":"2004","journal-title":"Psychol Methods."},{"key":"pone.0295593.ref051","doi-asserted-by":"crossref","first-page":"4","DOI":"10.1177\/109442810031002","article-title":"A review and synthesis of the measurement invariance literature: Suggestions, practices, and recommendations for organizational research.","volume":"3","author":"RJ Vandenberg","year":"2000","journal-title":"Organ Res Methods"},{"key":"pone.0295593.ref052","doi-asserted-by":"crossref","first-page":"464","DOI":"10.1080\/10705510701301834","article-title":"Sensitivity of goodness of fit indexes to lack of measurement invariance.","volume":"14","author":"FF Chen","year":"2007","journal-title":"Struct Equ Modeling"},{"key":"pone.0295593.ref053","article-title":"The MBESS R Package","author":"K Kelley","year":"2018","journal-title":"Computer software] MBESS Retrieved from: https:\/\/CRAN R-project org\/package = MBESS."},{"key":"pone.0295593.ref054","volume-title":"Mplus version 8 user\u2019s guide","author":"LK Muthen","year":"2017"},{"key":"pone.0295593.ref055","volume-title":"In: U.S. Food and Drug Administration [Internet].","author":"Office of the Commissioner","year":"2023"},{"key":"pone.0295593.ref056","volume-title":"Report to Congress on Traumatic Brain Injury in the United States: Epidemiology and Rehabilitation","author":"Centers for Disease Control and Prevention","year":"2015"},{"key":"pone.0295593.ref057","doi-asserted-by":"crossref","DOI":"10.4324\/9781315624358","volume-title":"An introduction to statistical concepts (4th edition).","author":"DL Hahs-Vaughn","year":"2020","edition":"4"},{"key":"pone.0295593.ref058","doi-asserted-by":"crossref","first-page":"572","DOI":"10.1136\/bmj.314.7080.572","article-title":"Cronbach\u2019s alpha.","volume":"314","author":"JM Bland","year":"1997","journal-title":"BMJ"},{"key":"pone.0295593.ref059","volume-title":"Principles and practice of structural equation modeling, Fourth Edition.","author":"RB Kline","year":"2015"},{"key":"pone.0295593.ref060","doi-asserted-by":"crossref","first-page":"740","DOI":"10.3389\/fpsyg.2018.00740","article-title":"The impact of partial measurement invariance on testing moderation for single and multi-level data.","volume":"9","author":"Y-Y Hsiao","year":"2018","journal-title":"Front Psychol"},{"key":"pone.0295593.ref061","doi-asserted-by":"crossref","first-page":"231","DOI":"10.1348\/000711003770480020","article-title":"Weak measurement invariance with respect to unmeasured variables: an implication of strict factorial invariance.","volume":"56","author":"GH Lubke","year":"2003","journal-title":"Br J Math Stat Psychol"},{"key":"pone.0295593.ref062","doi-asserted-by":"crossref","first-page":"321","DOI":"10.1136\/jnnp-2022-329683","article-title":"What is brain fog?","volume":"94","author":"L McWhirter","year":"2023","journal-title":"J Neurol Neurosurg Psychiatry"},{"key":"pone.0295593.ref063","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1080\/09638288.2022.2152503","article-title":"Is there evidence for a relationship between cognitive impairment and fatigue after acquired brain injury: a systematic review and meta-analysis.","author":"A Dillon","year":"2022","journal-title":"Disabil Rehabil"},{"key":"pone.0295593.ref064","doi-asserted-by":"crossref","first-page":"E249","DOI":"10.1097\/HTR.0000000000000710","article-title":"Fatigue after traumatic brain injury: A systematic review","volume":"37","author":"A Ali","year":"2022","journal-title":"J Head Trauma Rehabil"}],"container-title":["PLOS ONE"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0295593","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,12,11]],"date-time":"2023-12-11T18:28:55Z","timestamp":1702319335000},"score":1,"resource":{"primary":{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0295593"}},"subtitle":[],"editor":[{"given":"Ali B.","family":"Mahmoud","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"editor"}]}],"short-title":[],"issued":{"date-parts":[[2023,12,11]]},"references-count":64,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2023,12,11]]}},"URL":"https:\/\/doi.org\/10.1371\/journal.pone.0295593","relation":{},"ISSN":["1932-6203"],"issn-type":[{"value":"1932-6203","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,12,11]]}}}