Patients with fibromyalgia syndrome (FMS纤维肌痛综合症) typically have widespread chronic pain and fatigue. For those with low vitamin D levels, vitamin D supplements can reduce pain and may be a cost-effective alternative or adjunct（附属的） to other treatment, say researchers in the current issue of PAIN®. In addition to pain and fatigue, individuals diagnosed with FMS may experience sleep disorders, morning stiffness, poor concentration, and occasionally mild-to-severe mental symptoms such as anxiety or depression. The condition can have a significant impact on the patient's quality of life, resulting in loss of employment and/or withdrawal from social life. There is no cure, and no treatment will address all of the symptoms, but some symptoms may be alleviated by physical therapy, cognitive behavioral therapy, temporary drug therapy (such as amitriptyline, duloxetine, or pregabaline) and multimodal therapies.

Calcifediol (also known as calcidiol, 25-hydroxycholecalciferol, or 25-hydroxyvitamin D (OH)D) is a prehormone produced in the liver by the enzyme cholecalciferol (vitamin D3). Calcifediol is then converted to calcitriol (1,25-(OH)2D3), which is the active form of vitamin D. The concentration of calcifediol in blood is considered the best indicator of vitamin D status.

Researchers hypothesized that vitamin D supplementation would reduce the degree of chronic pain experienced by FMS patients with low levels of calcifediol and also might improve other symptoms. "Low blood levels of calcifediol are especially common in patients with severe pain and fibromyalgia. But although the role of calcifediol in the perception of chronic pain is a widely discussed subject, we lack clear evidence of the role of vitamin D supplementation in fibromyalgia patients," says lead investigator Florian Wepner, MD, of the Department of Orthopaedic Pain Management, Spine Unit, Orthopaedic Hospital, Speising, Vienna, Austria. "We therefore set out to determine whether raising the calcifediol levels in these patients would alleviate pain and cause a general improvement in concomitant（相伴的） disorders."