Is vitamin D linked to fatigue in patients with rheumatoid arthritis?

Takeaway

• Vitamin D was not associated with fatigue in patients with established rheumatoid arthritis (RA).
• However, fatigue correlated with RA disease activity, psychological distress and pain.

Why this matters

• Association of vitamin D status with depression and anxiety has been investigated in patients with RA, but limited studies showed the potential association between vitamin D and fatigue.

Study design

• A cross-sectional study of 169 patients with established RA.
• Fatigue evaluated by the Chalder fatigue questionnaire and serum 25(OH)D level evaluated by liquid chromatography-tandem mass spectrometry.
• Fatigue was compared across 4 groups based on the levels of serum 25(OH)D at 30, 50 and 75 nmol/L.
• Funding: None disclosed.

Key results

• Of 169 patients with RA, 116 (68.6%) had low RA disease activity, showing Disease Activity Score 28-joint count C- reactive protein (DAS28-CRP score, <3.2).
• Patient’s mean (standard deviation) serum 25(OH)D level was 56.3 (21.2) nmol/L; of which, 77 (46%) patients had serum 25(OH)D concentration <50 nmol/L and 12 (7.1%) had <30 nmol/L.
• A weak and non-significant association was observed between fatigue and serum 25(OH)D level (r=−0.14; 95% CI, −0.29 to 0.03; P=.08).
• Multivariate analysis showed fatigue was significantly associated with RA disease activity (DAS28-CRP: β=0.66; 95% CI, 0.14-1.18; P=.01), psychological distress (β=0.32; 95% CI, 0.21-0.44; P<.001) and pain (β=0.47; 95% CI, 0.14-0.79; P=.01), but not with serum 25(OH)D level (β=−0.01; 95% CI, −0.04 to 0.02; P=.66).
• Fatigue score did not differ across varying levels of serum 25(OH)D (P=.37).

Limitations

• Single-centre study.