Orthostatic Cognitive Dysfunction in Postural Tachycardia Syndrome After Rapid Water Drinking

Abstract

Background: Postural tachycardia syndrome (POTS) is a form of autonomic dysregulation and is characterized by an excessive heart rate (HR) increment upon the upright body position while blood pressure is maintained. Patients experience typical symptoms of orthostatic intolerance such as dizziness, nausea and cognitive impairments. The present study assessed position-dependent attentional and cognitive functioning in POTS patients compared to healthy subjects and tested the response of cognitive performance to acute water intake. Methods: Data was obtained from eight patients with neuropathic POTS and eight healthy subjects of similar age and gender. All participants completed questionnaires that assessed health-related quality of life and depression and underwent four rounds of neuropsychological testing overall, each before and after the intake of 500 ml still mineral water and both in the supine and in the upright posture. Results: Postural tachycardia syndrome patients showed deficits in working memory (WM) exclusively in the upright position compared to healthy subjects, but no position-dependent impairments in alertness or divided attention. Rapid water ingestion had a beneficial effect on WM in the upright posture, lead to a decrease in HR increment and to an improvement of subjective symptom experience. Conclusion: The results provide support for the occurrence of purely orthostatic cognitive deficits in POTS, especially when increased executive control and cognitive resources are required and document a favorable effect of water intake on cognitive performance. These findings have important implications for the management of cognitive symptoms in POTS as high water intake is an easy and accessible strategy.

Keywords: alertness; cognitive impairment; divided attention; orthostatic intolerance; postural tachycardia syndrome; water intake; working memory.

FIGURE 1

Study protocol. Participants completed four rounds of the same sequence of neuropsychological tests of the test battery “Test of Attentional Performance” (TAP; Zimmermann and Fimm, 2007). BP, blood pressure; rep., repetition; HUT, head-up tilt.

FIGURE 2

Neuropsychological data. Bar graphs showing results of four rounds of neuropsychological testing in patients with POTS (white bars) and control subjects (gray bars) in the supine and 60° head-up tilt (HUT) position, each before and after the intake of water. (A) Tonic alertness. (B) Phasic alertness. (C) Divided attention auditory. (D) Divided attention visual. (E) Working memory reaction time. (F) Working memory error rates. Y-axes of plots A to E indicate reaction time (ms). Y-axis of plot F indicates cumulative number of errors and omissions. Values are given as means ± S.E.M. ^∗P ≤ 0.05; ^∗∗P ≤ 0.01.