Fibromyalgia patients with lower serotonin levels are more likely to have a severe form of the disease, while there is no apparent relationship between vitamin D levels and disease severity, researchers found.
The study, “Clinical association of vitamin D and serotonin levels among patients with fibromyalgia syndrome,” was published in the journal Neuropsychiatric Disease and Treatment.
Fibromyalgia is the second most common rheumatic disorder. Common symptoms include chronic pain, mood changes, tiredness, and sleep disorders.
The exact cause of fibromyalgia remains unknown, but studies have suggested that the dysregulation, or improper working, of specific proteins and small molecules are related to disease progression and severity.
Vitamin D is essential for the function of muscles and bones, and its deficiency can lead to chronic pain. Studies have connected fibromyalgia to low levels of this vitamin. However, the direct relationship between Vitamin D and fibromyalgia is still unclear.
Serotonin is a neurotransmitter — molecules that mediate the communication between neurons — whose deficiency is associated with several behavioral disorders, depression, and tiredness. Serotonin deficiency also has been associated with fibromyalgia, but studies on this relationship are lacking.
To learn more, researchers from Saudi and Egyptian institutions calculated the prevalence of vitamin D and serotonin deficiency among 40 people with fibromyalgia, and assessed whether these levels were related to disease severity using the revised Fibromyalgia Impact Questionnaire (FIQR). In this scoring system, a higher score indicates increased severity.
The researchers found that 42.5% of the patients were considered to have mild (17.5%) or moderate (25%) fibromyalgia, and 57.5% were diagnosed with severe or extreme fibromyalgia.
More than half the participants (60%) had serotonin and vitamin D deficiencies. These patients also had a higher incidence of high blood pressure and obesity than the general population.
Those with lower serotonin levels tended to have more severe fibromyalgia, as seen by higher FIQR scores. There was no apparent relationship between vitamin D levels and disease severity.
“These results support the importance of serotonin medication to improve the symptoms of [fibromyalgia] patients. Given that serotonin levels play a significant role in the [fibromyalgia] diagnosis, doctors should request testing for the serum serotonin level in any patient suspected of having [fibromyalgia],” the researchers said.
The researchers noted that the study sample was small, and that future studies with more participants should further investigate the relationship between fibromyalgia, serotonin, and vitamin D.