Restless Legs Syndrome Tied to Gut Health

Megan Brooks

June 13, 2019

SAN ANTONIO — Preliminary research suggests an association between small intestine bacterial overgrowth (SIBO) and restless legs syndrome (RLS), supporting emerging research linking gut microbial health to sleep health.

While the study is ongoing and recruitment just beginning, the researchers found SIBO in all 7 RLS patients studied to date.

"We found very high rates of small intestinal bacterial overgrowth in these RLS patients," lead investigator Daniel J. Blum, PhD, adjunct clinical instructor at Stanford Center for Sleep Sciences and Medicine in Redwood City, California, told Medscape Medical News. Exploring this relationship further could lead to new ways to detect, prevent, and treat RLS, he said.

The study was presented here at SLEEP 2019: 33rd Annual Meeting of the Associated Professional Sleep Societies.

RLS Poorly Understood

Although the cause of RLS is not fully understood, a relative state of brain iron deficiency has been described in patients with RLS and appears to induce changes in several pathways known to be involved in the disease, said Blum.

Insufficient iron may be secondary to dietary iron deficiency or, potentially, gut inflammation. Blum and colleagues hypothesized that SIBO, a condition associated with gut dysbiosis, may be associated with RLS.

Participants for the study were recruited at the Stanford Sleep Center for 3 groups: RLS and low peripheral iron stores (<50 ng/mL and/or transferrin saturation <18%), RLS and normal peripheral iron stores, and insomnia (control group).

As part of the study, they completed questionnaires concerning sleep and SIBO symptoms and took home a fecal collection kit and a SIBO breath test kit. Fecal samples were examined by the University of Minnesota Genomics Center, and SIBO breath samples were evaluated by Aerodiagnostics, a Massachusetts-based medical laboratory, for hydrogen and methane abnormalities.

The 7 participants diagnosed with RLS who have completed the protocol to date include 3 men and 4 women. All had poor sleep quality based on the Pittsburgh Sleep Quality Index and moderate to severe symptoms based on the International Restless Legs Scale. 

SIBO was present in all 7 participants (100%). In contrast, SIBO rates in the general population are estimated to be between 6% and 15%, suggesting SIBO may be much more common in the RLS population, Blum reported.

"There is an unpublished study showing that [for] people who have this overlap of SIBO and RLS, if you treat the SIBO, the RLS significantly improves," Blum said.

New Insight

Commenting on the study, American Academy of Sleep Medicine spokesperson Nitun Verma, MD, noted that the study is "small but very interesting."

"Restless legs is a relatively common disorder and we have really not gotten to the bottom of why people have it. Patients want to know why they have restless legs and it's terrible that we can't give them a good answer. This study opens the door to deeper research on potential causation," said Verma, who was not involved with the current study.

Dianne Augelli, MD, sleep medicine expert at Weill Cornell Medicine and NewYork-Presbyterian Hospital in New York City, also believes the SIBO-RLS link is "interesting" but cautioned that "much larger studies are needed" to replicate the results. She was not associated with the current research.

In addition, it can be "complicated" to treat SIBO, Augelli told Medscape Medical News, "and that treatment may lead down a pathway that can cause harm. Do we treat with antibiotics and end up making something else worse?"

The study was funded by a Pau Innovation Gift Fund Seed Grant. Blum, Verma, and Augelli have disclosed no relevant financial relationships.

SLEEP 2019: 33rd Annual Meeting of the Associated Professional Sleep Societies: Abstract 0009. Presented June 9, 2019.

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