People with fibromyalgia have significantly higher variability in the interval between consecutive heartbeats compared to healthy people, study published in the Annals of Rehabilitation Medicine found.

Although similar findings have been reported in previous studies, observational differences among them resulted in a lack of consensus. The classical way to analyze heart beat variability was not always able to distinguish differences in the heart rate of people with and without fibromyalgia.

The study, titled “Heart rate variability for quantification of autonomic dysfunction in fibromyalgia,” describes a new statistical method of analysis that is able to detect a consistent difference between groups of people with fibromyalgia groups and those in good health.

Using this new method, symptoms which are typically assessed subjectively by a questionnaire called COMPASS31 can now be quantified objectively. “[This] is a valuable parameter for autonomic nervous system function and can be used to quantify subjective autonomic symptoms in patients with fibromyalgia,” the researchers wrote.

Conducted at the Seoul Medical Center in Korea, the study involved 16 people with fibromyalgia, ages 37 to 60, and 16 age-matched healthy controls. All participants had their heart rate variability measured under normal breathing and rate controlled breathing conditions, with each asked to take six breaths per minute.

No significant differences in heart rate variability under either breathing condition were observed between the two groups using simple comparisons. However, combining those comparisons into a single statistical variable resulted in significant and reproducible differences between them. These differences were independent from the breathing condition.

According to the authors, the next step in strengthening these findings would be to analyze a larger group of people.

Fibromyalgia is a chronic pain syndrome characterized by generalized pain in muscles and bones, fatigue, reduced muscle strength, depression, and decreased quality of life. Although the exact cause of fibromyalgia is not fully understood, autonomic nervous system dysfunction is thought to be associated with pain and psychosocial stress. Heart rate variability analysis may be a useful tool to assess autonomic nervous system dysfunction in people with fibromyalgia.