Clinically accessible tools for documenting the impact of Orthostatic Intolerance on symptoms and function in ME/CFS, by Jihyun Lee, Pelle Wall, Chris Kimler, Lucinda Bateman, Suzanne D Vernon in Work vol. 66, no. 2, pp. 257-263, 2020 [doi: 10.3233/WOR-203169]


Research abstract:


Clinical observations have indicated that hours of upright activity (HUA) reported by Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) patients correlated with orthostatic symptoms and impaired physical function. This study examined the relationship between HUA and orthostatic intolerance (OI).


Twenty-five female ME/CFS subjects and 25 age and race matched female healthy controls (HCs) were enrolled. Subjects reported HUA (defined as hours per day spent with feet on the floor) and completed questionnaires to assess the impact of OI on daily activities and symptoms. ME/CFS patients were categorized into those with <5 HUA and ≥5 HUA and analyzed by employment status. Data analysis used one-way ANOVA.


ME/CFS patients had fewer HUA, worse symptoms and greater interference with daily activities due to OI than HCs. The <5 HUA ME/CFS subjects had more severe OI related symptoms than ≥5 HUA ME/CFS subjects even though OI interfered with daily activities similarly.

Only 33% of ME/CFS subjects were employed and all were ≥5 HUA ME/CFS subjects with an average HUA of 8.


ME/CFS subjects experienced more frequent and severe OI symptoms, higher interference with daily activities, and reduced ability to work than HCs. Reported HUA and assessment of OI using standardized instruments may be useful clinical tools for physicians in the diagnosis, treatment and management of ME/CFS patients.



Orthostatic intolerance (OI) is defined as the development of symptoms upon assuming and maintaining upright postures that are alleviated by recumbency . “Symptoms of orthostatic intolerance are those caused primarily by

  1. cerebral under-perfusion (such as lightheadedness, near-syncope or syncope, impaired concentration, headaches, and dimming or blurring of vision), or
  2. sympathetic nervous system activation (such as forceful beating of the heart, palpitations, tremulousness, and chest pain), and
  3. other common signs and symptoms of orthostatic intolerance such as fatigue, a feeling of weakness, intolerance to low-impact exercise, nausea, abdominal pain, facial pallor, nervousness, and shortness of breath.”

Symptoms of OI are exacerbated by prolonged periods of upright posture and various daily experiences such as exercise, warm environments or large meals. Circumstances in daily life that can easily exacerbate OI include standing in line, grocery shopping, hot weather, overheated rooms, hot showers or baths and even sitting to eat a meal.

Clinicians should document patients’ symptoms and function in order to determine the impact of illness on the performance of daily activities and occupational responsibilities.

…Our clinical experience with over 1,000 ME/CFS patients has indicated that their disease severity can be gauged by hours of upright activity which we define as time with feet on the floor over a 24-hour period. Severely ill ME/CFS patients reported 0 to 4 hours with their feet on the floor while moderately ill patients reported having their feet on the floor for 5 to 8 hours. This observation led us to explore which ME/CFS symptoms were associated with an upright activity.

In this study, subjects were asked to report hours of upright activity (HUA) by estimating the hours per day spent in the following 4 positions over the past week:

  1. hours upright (standing, walking, running),
  2. hours sitting with feet on the floor,
  3. hours reclining or sitting with feet elevated and,
  4. hours lying down (includes sleeping).

We also used a standardized orthostatic questionnaire to evaluate how being in upright positions affected daily activities and the severity of symptoms. We found that both assessment tools can be easily administered and are effective at documenting the impact of orthostatic intolerance on symptom severity and daily activities in ME/CFS patients.

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