Low vitamin D linked to musculoskeletal pain

Is vitamin D a neglected analgesic for chronic musculoskeletal pain? A 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. Her opinion was based 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. 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. All of the participants underwent a comprehensive clinical examination, during which pain was assessed using the Brief Pain Inventory and Visual Analog 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.”

All the patients completed 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 by monthly intervals during follow-up, as was physical performance using activities of daily living, grip strength, 6 minute walk distance, and the timed Get Up and Go Test of mobility. Additionally, serum vitamin D was measured by Liaison immunoassay and levels between 10 and 30 ng/mL were classified as vitamin 0 insufficiency and levels lower than 10 ng/mL were classified as vitamin D deficiency.

In musculoskeletal patients, the mean 25-hydroxyvitamin D level was 18.4 ng/mL, compared with 28.9 ng/mL in the control group, which represents a statistically significant difference.

“The overall prevalence of suboptimal vitamin D levels among patients was 70% vs. 32% in the controls,” 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 single-site chronic pain.”

After multivariate adjustment, “chronic, multisite, musculoskeletal pain was associated with lower levels of 25-hydroxyvitamin D, and lower levels of vitamin D correlated with pain severity and poor physical performance.” One likely contributing factor is that sun exposure in the chronic pain group was lower than in controls, with 40% of the pain patients reporting that they had fewer than 15 minutes of sun exposure weekly compared with 11% of controls, likely because of limitations on physical activity associated with chronic pain, she said.