{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,25]],"date-time":"2026-08-25T03:32:43Z","timestamp":1787628763476,"version":"build-2736575974"},"reference-count":36,"publisher":"Wiley","issue":"4","license":[{"start":{"date-parts":[[2013,11,29]],"date-time":"2013-11-29T00:00:00Z","timestamp":1385683200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"name":"Alison Hunter Memorial Foundation"},{"DOI":"10.13039\/501100001220","name":"Medical Advances Without Animals Trust","doi-asserted-by":"crossref","id":[{"id":"10.13039\/501100001220","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J Intern Med"],"published-print":{"date-parts":[[2014,4]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Objective<\/jats:title><jats:p>Patients with chronic fatigue syndrome (<jats:styled-content style=\"fixed-case\">CFS<\/jats:styled-content>) are frequently diagnosed with comorbid postural orthostatic tachycardia syndrome (<jats:styled-content style=\"fixed-case\">POTS<\/jats:styled-content>), suggesting a shared pathogenesis. The aim of this study was to examine the relationship between demographic characteristics, autonomic functioning and fatigue levels amongst <jats:styled-content style=\"fixed-case\">CFS<\/jats:styled-content> patients with and without comorbid <jats:styled-content style=\"fixed-case\">POTS<\/jats:styled-content>.<\/jats:p><\/jats:sec><jats:sec><jats:title>Design and setting<\/jats:title><jats:p>All patients presenting to the <jats:styled-content style=\"fixed-case\">CFS D<\/jats:styled-content>iscovery <jats:styled-content style=\"fixed-case\">C<\/jats:styled-content>linic between 2009 and 2012 completed a 20\u2010min standing task as part of their initial assessment. Heart rate and pulse pressure were recorded at baseline, at 2\u2010min intervals poststanding, at the end of the task and following a recovery period. Average heart rate and pulse pressure variability were calculated from this data. Age, gender, length of illness and self\u2010reported fatigue scores were also recorded. <jats:styled-content style=\"fixed-case\">POTS<\/jats:styled-content> patients were diagnosed by an orthostatic increase in heart rate &gt;30\u00a0beats per min, concomitant symptoms of orthostatic intolerance and no orthostatic hypotension. Differences in autonomic functioning between <jats:styled-content style=\"fixed-case\">POTS<\/jats:styled-content> and <jats:styled-content style=\"fixed-case\">CFS<\/jats:styled-content> patients were compared using independent samples <jats:italic>t<\/jats:italic>\u2010tests, whilst logistic and linear regressions were performed to examine the contribution of autonomic functioning to task completion and perceived fatigue, respectively.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Comorbidity of <jats:styled-content style=\"fixed-case\">CFS<\/jats:styled-content> and <jats:styled-content style=\"fixed-case\">POTS<\/jats:styled-content> (<jats:styled-content style=\"fixed-case\">CFS<\/jats:styled-content>\u2010<jats:styled-content style=\"fixed-case\">POTS<\/jats:styled-content>) was observed in 11% (33\/306) of patients. <jats:styled-content style=\"fixed-case\">CFS<\/jats:styled-content>\u2010<jats:styled-content style=\"fixed-case\">POTS<\/jats:styled-content> patients were significantly younger (<jats:italic>P\u00a0<\/jats:italic>&lt;<jats:italic>\u00a0<\/jats:italic>0.001), had a shorter length of illness (<jats:italic>P\u00a0<\/jats:italic>=<jats:italic>\u00a0<\/jats:italic>0.034), experienced greater task difficulty (<jats:italic>P\u00a0<\/jats:italic>=<jats:italic>\u00a0<\/jats:italic>0.002) and were able to stand for significantly shorter periods compared to the <jats:styled-content style=\"fixed-case\">CFS<\/jats:styled-content>\u2010only patients (<jats:italic>P\u00a0<\/jats:italic>&lt;<jats:italic>\u00a0<\/jats:italic>0.001). <jats:styled-content style=\"fixed-case\">CFS<\/jats:styled-content>\u2010<jats:styled-content style=\"fixed-case\">POTS<\/jats:styled-content> patients experienced significantly lower baseline diastolic blood pressure (<jats:italic>P\u00a0<\/jats:italic>=<jats:italic>\u00a0<\/jats:italic>0.002), significantly higher heart rate and lower pulse pressures at each standing measurement. Early heart rate changes (<jats:italic>P\u00a0<\/jats:italic>=<jats:italic>\u00a0<\/jats:italic>0.002) and overall heart rate change (<jats:italic>P\u00a0<\/jats:italic>&lt;<jats:italic>\u00a0<\/jats:italic>0.001) were significant predictors of completion status, whereas heart rate variability (<jats:italic>P\u00a0<\/jats:italic>&lt;<jats:italic>\u00a0<\/jats:italic>0.001) and female gender (<jats:italic>P\u00a0<\/jats:italic>&lt;<jats:italic>\u00a0<\/jats:italic>0.001) were significant predictors of increased perceived task difficulty.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>Haemodynamic and demographic differences between <jats:styled-content style=\"fixed-case\">CFS<\/jats:styled-content>\u2010<jats:styled-content style=\"fixed-case\">POTS<\/jats:styled-content> and <jats:styled-content style=\"fixed-case\">CFS<\/jats:styled-content>\u2010only patients suggest that the former group reflects a distinct subgroup of the <jats:styled-content style=\"fixed-case\">CFS<\/jats:styled-content> population. The findings highlight the utility of screening younger patients with fatigue for <jats:styled-content style=\"fixed-case\">POTS<\/jats:styled-content>, and identified heart rate variability as an important marker of fatigue for <jats:styled-content style=\"fixed-case\">CFS<\/jats:styled-content> patients in general.<\/jats:p><\/jats:sec>","DOI":"10.1111\/joim.12161","type":"journal-article","created":{"date-parts":[[2013,11,9]],"date-time":"2013-11-09T12:12:52Z","timestamp":1383999172000},"page":"409-417","source":"Crossref","is-referenced-by-count":62,"title":["Comorbidity of postural orthostatic tachycardia syndrome and chronic fatigue syndrome in an <scp>A<\/scp>ustralian cohort"],"prefix":"10.1111","volume":"275","author":[{"given":"G. 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