Fibromyalgia is a mysterious and misunderstood illness, but researchers may have uncovered at least one key to the disease's origin: insulin resistance.
The new research compared a small group of people with fibromyalgia to two groups of healthy people and noted that a long-term measure of blood sugar levels was higher in the people with fibromyalgia. Insulin resistance develops when the body starts to struggle with breaking down sugar.
To see if treating those higher blood sugar levels might help, the researchers gave people who had blood sugar levels in the pre-diabetic range or higher a diabetes medication called metformin. People taking metformin reported significantly lower pain scores, according to the study.
"We combined metformin with standard drugs used for fibromyalgia and saw a much greater degree of pain relief," said study author Dr. Miguel Pappolla. He is a professor of neurology at the University of Texas Medical Branch at Galveston.
In fact, Pappolla said, the additional pain relief was so significant that the researchers actually called patients on different days to re-check their pain scores.
Because this is a preliminary finding, the researchers aren't sure how insulin resistance might contribute to fibromyalgia or how metformin might reduce pain. "Metformin may have some analgesic [pain-relieving] activity on its own," Pappolla said.
Fibromyalgia is a condition that causes widespread pain, fatigue, sleep problems and distress, according to the U.S. Centers for Disease Control and Prevention. Even celebrities aren't spared from this painful condition -- Lady Gaga reportedly had to cancel concerts on her tour due to pain from fibromyalgia.
Though the cause of the disorder isn't clear, it appears that people with fibromyalgia may be more sensitive to pain than other people -- what the CDC calls abnormal pain processing.
Pappolla said that studies have shown differences in the brain between people with fibromyalgia and those without, such as areas with a lower blood flow than expected. The researchers noted that similar problems have been seen in people with diabetes.
The study included 23 people with fibromyalgia. The researchers compared their hemoglobin A1c levels to large groups of healthy people from two other studies. Hemoglobin A1c is a simple blood test that measures what someone's blood sugar levels were during the past two or three months. A level of 5.7% to 6.4% is considered pre-diabetes, according to the American Diabetes Association. A level of 6.5% or higher means a person has diabetes.
Only six of those with fibromyalgia had normal blood sugar levels. Sixteen had levels considered pre-diabetes and one met the criteria for diabetes.
When the researchers compared the average blood sugar levels of the fibromyalgia group to healthy age-matched people in the other studies, they saw that the blood sugar levels were higher in the people with fibromyalgia, suggesting insulin resistance.
The findings were published online recently in the journal PLOS ONE.
Dr. Edward Rubin, an anesthesiologist and pain management specialist at Long Island Jewish Medical Center, said, "It's interesting that there's a possible connection between fibromyalgia and blood sugar. We've been attacking the symptoms of fibromyalgia, but we don't have a good understanding of the root cause of fibromyalgia."
Rubin, who wasn't involved in the study, said there may be enough evidence here to try metformin along with other medications used for fibromyalgia for people whose blood sugar levels fall outside of the normal range, to see if they have a positive response.
Dr. Bharat Kumar, from the University of Iowa Hospitals and Clinics, said this study shows people with the disease that there is hope.
"People with fibromyalgia are often told [falsely] that they have a disease that simply cannot be managed. This article shows that it's not true. Although it's unclear if metformin will work for every person suffering from fibromyalgia, there is active research into finding solutions for this frustrating and overlooked condition," he said.
Kumar said it's biologically plausible that insulin could have an effect on pain. "We know that other hormone abnormalities can cause fibromyalgia-like symptoms, so [this finding] is not too surprising," he added.
Still, he said, he didn't expect that metformin would be a "silver bullet" for all fibromyalgia pain. He said there are likely a number of causes of the disease.
Learn more about fibromyalgia from the American College of Rheumatology.