The relationship between vitamin D and rheumatoid arthritis (RA) activity remains controversial. RA is a cardiovascular risk factor. A low level of vitamin D may increase blood pressure (BP) and decrease HDL-cholesterol. We aimed to determine the prevalence of vitamin D deficiency in RA patients compared to controls, and also to investigate the relationship between vitamin D and RA activity, and between vitamin D and cardiovascular risk factors.
Patients in the COMEDRA study with established inactive RA (1987 ACR criteria) were matched with subjects from the NUTRINET-SANTE cohort (age, gender, latitude, sampling season). Vitamin D deficiency was defined as <10 ng/mL, and insufficiency as 10 to 29.9 ng/mL.
Eight hundred and ninety-four RA patients were analysed, of which 861 were matched with controls. The prevalence of vitamin D insufficiency and deficiency was lower in RA patients than in controls: 480 (55.8%) vs. 508 (59%) and 31 (3.6%) vs. 45 (5.23%), respectively; p=0.04. There was an inverse correlation between vitamin D levels and RA activity assessed by DAS28-CRP (p=0.01), SDAI (p<0.001) and CDAI (p=0.001), but not DAS28-ESR after adjustment for age, gender, inclusion season, body mass index (BMI), vitamin D supplementation, disease duration, RF or anti-CCP status and RA treatments. Vitamin D levels were inversely correlated with BMI (p<0.001), but not with BP, total cholesterol, LDL-cholesterol, HDL-cholesterol or blood glucose.
This study demonstrates that vitamin D is inversely correlated with RA activity and BMI, but not with other cardiovascular risk factors.