Is vitamin D a neglected analgesic for chronic musculoskeletal pain? Dr. Suzan Abou-Raya, professor of geriatric medicine at the University of Alexandria in Egypt, thinks it could be and recommends that physicians should consider oral supplementation for all pain patients. Dr. Abou-Raya based her opinion on the findings of a recent study in which she and her colleagues evaluated the association between vitamin D status and chronic musculoskeletal pain in a cohort of community-dwelling older adults.
The investigators compared the vitamin D status of 265 adults aged 65 years and older who presented to their institution for musculoskeletal pain management with that of 200 other adults who were free of chronic musculoskeletal pain. These controls were matched to the cases by age, sex, and body mass index, according to Dr. Abou-Raya. Individuals with known vitamin D deficiency and calcium abnormality were excluded from the study, as were those with severe cognitive impairment or infectious, blood, hepatic, and renal disorders.
All of the participants in the study, which was conducted during the months of April through September to account for seasonal variation, underwent an initial survey about sun exposure and nutritional intake to assess daily intake of vitamin D and calcium, Dr. Abou-Raya explained. All of the participants underwent a comprehensive clinical examination, during which pain was assessed using the Brief Pain Inventory and Visual Analogue Scale. "Chronic pain was defined as pain that was present in the previous month and for at least 3 months during the previous year, and it was assessed according to the site of pain, the overall severity of the pain, and interference with daily activities," she said. Additionally, all of the patients completed a joint pain questionnaire to assess chronic musculoskeletal pain in the hands and wrists, shoulders, back, hips, knees, and feet, and they were directed to record daily pain in a diary.
Levels of pain were assessed at monthly intervals during follow-up, as was physical performance using activities of daily living, grip strength, six-minute walk distance, and the timed Get up and Go Test of mobility, Dr. Abou-Raya stated. Additionally, serum vitamin D was measured by Liaison immunoassay and levels between 10 and 30 ng/ml were classified as vitamin D insufficiency and levels lower than 10 ng/ml were classified as vitamin D deficiency, she noted.
In musculoskeletal patients, the mean 25-hydroxy vitamin D level was 18.4 ng/ml compared with 28.9 ng/ml in the control group, which represents a statistically significant difference, Dr. Abou-Raya reported. "The overall prevalence of suboptimal vitamin D levels among patients was 70% vs. 32% in the controls," she said, noting that 41% of the chronic musculoskeletal pain patients and only 1% of the controls met the criteria for vitamin D deficiency. "We also found that patients with multisite chronic pain had significantly lower levels of vitamin D compared with patients reporting sing-site chronic pain, and patients with more severe pain at baseline had significantly lower vitamin D levels than those with less severe pain."
After multivariate adjustment, "chronic, multisite, musculoskeletal pain was associated with lower levels of 25-hydroxy vitamin D, and lower levels of vitamin D correlated with pain severity and poor physical performance," Dr. Abou-Raya stated. One likely contributing factor is that sun exposure in the chronic pain group was significantly lower than that of the controls, with 40% of the pain patients reporting that they received fewer than 15 minutes of sun exposure weekly compared with 11% of the controls, likely due to limitations on physical activity associated with chronic pain, she said.
The results of this observational study should not be used to infer causation, Dr. Abou-Raya stressed. "They simply demonstrate that patients with chronic musculoskeletal pain have lower levels of vitamin D compared with individuals who are pain free, thus the possibility of inadequate vitamin D should be considered in the differential diagnosis of chronic musculoskeletal pain sufferers," she said at the annual European Congress of Rheumatology.
The implication of the findings, she continued, "is that all patients with chronic musculoskeletal pain should receive oral vitamin D supplementation, as optimal vitamin D levels appear to be associated with less pain and better physical performance."
Dr. Abou-Raya disclosed having no financial conflicts of interest related to her presentation.