Ocon, Anthony J, Messer, Zachary R, Medow, Marvin S et al. · Clinical science (London, England : 1979) · 2012 · DOI
This study tested whether standing at increasing angles on a tilt table—a procedure that stresses the body's ability to maintain blood flow while upright—makes 'brain fog' worse in people with ME/CFS who also have POTS (a condition causing rapid heartbeat when standing). Researchers found that when people with CFS/POTS stood at steeper angles while doing concentration and memory tests, their performance got worse compared to healthy people, suggesting that orthostatic stress (the challenge of staying upright) does interfere with thinking and memory.
This study provides mechanistic evidence that orthostatic stress directly impairs cognition in CFS/POTS patients, validating a core patient complaint ('mental fog') and suggesting orthostatic intolerance contributes to neurocognitive dysfunction beyond mere fatigue. Understanding this link may help clinicians recognize cognitive impairment as an orthostatic manifestation and inform management strategies that minimize positional challenges during vulnerable periods.
This study does not identify the specific neurological mechanism causing cognitive impairment during orthostatic stress, since CBFV changes were not associated with performance—ruling out global cerebral hypoperfusion but leaving alternative mechanisms (regional perfusion changes, autonomic dysregulation, metabolic stress) unexplored. The small sample size and single time-point design also limit generalizability to the broader ME/CFS population and do not establish whether chronic recurrent orthostatic stress contributes to long-term cognitive decline.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Ocon, Anthony J, Messer, Zachary R, Medow, Marvin S, & Stewart, Julian M (2012). Increasing orthostatic stress impairs neurocognitive functioning in chronic fatigue syndrome with postural tachycardia syndrome.. Clinical science (London, England : 1979). https://doi.org/10.1042/CS20110241
BibTeX
@article{mecfsatlas-ocon-2012-increasing-orthostatic,
author = {Ocon, Anthony J and Messer, Zachary R and Medow, Marvin S and Stewart, Julian M},
title = {Increasing orthostatic stress impairs neurocognitive functioning in chronic fatigue syndrome with postural tachycardia syndrome.},
journal = {Clinical science (London, England : 1979)},
year = {2012},
doi = {10.1042/CS20110241},
note = {PubMed: 21919887},
url = {https://www.mecfsatlas.com/evidence/ocon-2012-increasing-orthostatic},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/ocon-2012-increasing-orthostatic
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