April 09, 2015
3 min read

Research links low vitamin D to higher disease activity in patients with RA

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Low levels of vitamin D in patients with rheumatoid arthritis were associated with higher disease activity and lower quality of life compared with patients with rheumatoid arthritis who had normal levels of vitamin D, according to recently published research.

Researchers studied a group of 97 consecutive patients with rheumatoid arthritis (RA) who did not take vitamin D supplementation. A control group of 28 patients with osteoarthritis (OA) was also enrolled. The patients with RA comprised 86 women and 11 men (mean age: 59.4 years) compared with 25 women and three men with OA (mean age: 56.2 years).

Data collected included information about disease duration; BMI; comorbidities; physical activity levels; the amount of time spent outdoors; and questionnaires such as the Beck Depression Inventory (BDI), Health Assessment Questionnaire (HAQ) and SF-36. The researchers used a VAS to measure the severity of pain and fatigue, and disease activity was assessed using the Disease Activity Score in 28 Joints (DAS28), which included measurements of each patient’s erythrocyte sedimentation rate (ESR), swollen and tender joint counts, and patients’ global assessment. Joint damage was assessed according to the Steinbrocker’s scale.

In addition to measuring vitamin D levels, laboratory tests included a complete blood count, concentrations of creatinine, calcium, phosphates and parathyroid hormone.

The researchers observed vitamin D deficiency in 74 (76.3%) of the 97 patients with RA and in 22 (78.6%) of the patients with OA. Severe deficiency was seen in 37 (38.1%) of the patients with RA and in 10 (35.7%) of the patients with OA; however, the differences between the groups were statistically insignificant, according to the researchers.

Inverse correlations were found with parathyroid hormone serum concentrations and vitamin D. Patients with higher levels of vitamin D tended to have lower BMI, but the difference was not significant. Scores from the SF-36, BDI, DAS28 and HAQ were found to be slightly higher in patients with normal levels of vitamin D, according to the researchers.

In patients with active disease, a negative correlation was seen between vitamin D levels and DAS28 scores. A positive correlation was seen between the level of physical activity and healthy levels of vitamin D.

In 70 patients with RA who were treated for more than 1 year, 52 had insufficient levels of vitamin D, 28 of whom were severely deficient. All of the patients with RA who had insufficient levels of vitamin D had poorer scores on the BDI, HAQ and SF-36.

Univariate linear regression analysis revealed that the physical and mental component scores of the SF-36 and BDI and HAQ scores were significantly affected by vitamin D deficiency, both before and after adjusting for age, BMI, disease duration and other factors. However, when adjusted for physical activity, only scores for bodily pain and mental components of the SF-36 remained significant, the researchers reported. - by Shirley Pulawski

Disclosure: The researchers report no relevant financial disclosures.