title: Increasing orthostatic stress impairs neurocognitive functioning in chronic fatigue syndrome with postural tachycardia syndrome.
abstract: CFS (chronic fatigue syndrome) is commonly co-morbid with POTS (postural tachycardia syndrome). Individuals with CFS/POTS experience unrelenting fatigue, tachycardia during orthostatic stress and ill-defined neurocognitive impairment, often described as 'mental fog'. We hypothesized that orthostatic stress causes neurocognitive impairment in CFS/POTS related to decreased CBFV (cerebral blood flow velocity). A total of 16 CFS/POTS and 20 control subjects underwent graded tilt table testing (at 0, 15, 30, 45, 60 and 75°) with continuous cardiovascular, cerebrovascular, and respiratory monitoring and neurocognitive testing using an n-back task at each angle. The n-back task tests working memory, concentration, attention and information processing. The n-back task imposes increasing cognitive challenge with escalating (0-, 1-, 2-, 3- and 4-back) difficulty levels. Subject dropout due to orthostatic presyncope at each angle was similar between groups. There were no n-back accuracy or RT (reaction time) differences between groups while supine. CFS/POTS subjects responded less correctly during the n-back task test and had greater nRT (normalized RT) at 45, 60 and 75°. Furthermore, at 75° CFS/POTS subjects responded less correctly and had greater nRT than controls during the 2-, 3- and 4-back tests. Changes in CBFV were not different between the groups and were not associated with n-back task test scores. Thus we conclude that increasing orthostatic stress combined with a cognitive challenge impairs the neurocognitive abilities of working memory, accuracy and information processing in CFS/POTS, but that this is not related to changes in CBFV. Individuals with CFS/POTS should be aware that orthostatic stress may impair their neurocognitive abilities.
authors.affiliation: Department of Physiology, New York Medical College, Valhalla, NY, USA. anthony_ocon@nymc.edu
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Ocon
authors.forename: Zachary R
authors.initials: ZR
authors.lastname: Messer
authors.forename: Marvin S
authors.initials: MS
authors.lastname: Medow
authors.forename: Julian M
authors.initials: JM
authors.lastname: Stewart
mesh_terms: D000328:Adult; D001794:Blood Pressure; D002560:Cerebrovascular Circulation / Q000502:physiology; D003072:Cognition Disorders / Q000150:complications* / Q000503:physiopathology; D015673:Fatigue Syndrome, Chronic / Q000150:complications* / Q000503:physiopathology; D005260:Female; D006339:Heart Rate; D006801:Humans; D007024:Hypotension, Orthostatic / Q000150:complications* / Q000503:physiopathology; D008297:Male; D054972:Postural Orthostatic Tachycardia Syndrome / Q000150:complications* / Q000503:physiopathology; D013575:Syncope