Different studies have found difficulty standing (orthostatic intolerance) and autonomic nervous system dysfunction which explains this difficulty in people with fibromyalgia.
This dysfunction concerns the baroreflex which is one of the mechanisms responsible for keeping the blood pressure constant.
It includes the sympathetic and parasympathetic nervous systems that have opposite and complementary functions. The sympathetic system responds to stress by activating the body, the parasympathetic system induces a relaxation response. The dysfunctions observed in fibromyalgia correspond to an excessive activation of the sympathetic system.
One of them is the baroreflex that regulates blood pressure in the short term. Without this reflex, it would not be possible to stand without dizziness or fainting. Receptors, the baroreceptors, which are found on the nerves of the blood vessels, detect changes in blood pressure and transmit nerve impulses that control adjustments to vessel dilation and heart rate.
The baroreflex is particularly important for adaptation to sudden drop in blood pressure when moving from the supine position to the upright position while gravity draws blood to the lower body.
Antonio Roberto Zamunér and Ester Silva of the Federal University of Sao Carlos(Brazil), together with their colleagues, conducted this study with 35 women with fibromyalgia, with an average age of 48 (+ or – 9 years).
The baroreflex was evaluated by various analyzes from measurements of cardiac activity, blood pressure, and supine and standing breathing activity.
The impact of fibromyalgia on quality of life was assessed with the Fibromyalgia Impact Questionnaire (FIQ) (test) , which included the ability to perform daily tasks, and the pain was assessed with a visual scale.
The study concludes that participants with the lowest baroreflex activity while standing were those with fibromyalgia who decreased the quality of life the most and reported the most pain.
Difficulty in the standing position would contribute, or at least be related, to the severity of fibromyalgia as measured by the ability to function in everyday (FIQ) and pain.
Note that this link can be explained in itself, but it can also be reinforced by the fact that the deficit of baroreflex could be a manifestation of more generalized dysfunctions of the autonomic nervous system also affecting other systems.
Orthostatic intolerance (inability to stand for more than a short time) is one of the diagnostic criteria for chronic fatigue syndrome proposed by the American Institute of Medicine (IOM).
The research must continue.
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