Research: orthostatic stress impairs neurocognitive functioning, Clinical Science, 15 September 2011

Clin Sci (Lond). 2011 Sep 15. [Epub ahead of print]

Increasing orthostatic stress impairs neurocognitive functioning in Chronic Fatigue Syndrome with Postural Tachycardia Syndrome.

Ocon AJ, Messer Z, Medow M, Stewart J.
(MEA editorial note – academic affiliations not given)


Chronic Fatigue Syndrome (CFS) is commonly co-morbid with Postural Tachycardia Syndrome (POTS). 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 cerebral blood flow velocity (CBFV). 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 a N-back task at each angle. The N-back task tests working memory, concentration, attention, and information processing. The N-back 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 reaction time differences between groups while supine. CFS/POTS subjects responded less correctly during the N-back and had greater normalized reaction time at 45, 60, and 75°. Further, at 75° CFS/POTS subjects responded less correctly and had greater normalized reaction time 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 scores. Thus, we concluded 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.

PMID: 21919887 [PubMed – as supplied by publisher]


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