Seasonal and Treatment-Related Variation in 25-Hydroxy Vitamin D Concentration in Patients with Rheumatoid Arthritis

Area of Science:

• Rheumatology
• Endocrinology
• Nutritional Science

Background:

• 25-hydroxy vitamin D (25-OH-D) is crucial for bone health, immune function, and inflammation control.
• Emerging evidence links vitamin D metabolites to rheumatoid arthritis (RA) progression and neuropathic pain.
• Understanding factors influencing 25-OH-D levels in RA patients is vital for optimizing treatment and patient outcomes.

Purpose of the Study:

• To investigate the impact of rheumatoid arthritis pharmacotherapy (methotrexate vs. leflunomide) on serum 25-hydroxy vitamin D levels.
• To assess the influence of seasonal variations on 25-hydroxy vitamin D concentrations in RA patients.
• To explore correlations between 25-hydroxy vitamin D levels, RA duration, and specific treatment regimens.

Main Methods:

• Retrospective analysis of data from 101 rheumatoid arthritis patients treated for at least one year.
• All patients received daily supplementation of 2000 IU of 25-hydroxy vitamin D for over a year.
• Serum 25-hydroxy vitamin D levels were analyzed, considering treatment groups (methotrexate/leflunomide) and season of blood draw.

Main Results:

• Significant seasonal variation in serum 25-hydroxy vitamin D levels was observed (p = 0.004).
• Leflunomide treatment group showed significantly higher 25-OH-D levels (50.63 ± 17.73 ng/mL) compared to methotrexate (34.73 ± 14.04 ng/mL) during summer (p = 0.03).
• A negative correlation between 25-OH-D levels and RA duration was found in the summer population (r = -0.64 overall, -0.82 for LEF, -0.61 for MTX).
• Vitamin D deficiency (<20 ng/mL) affected 28.7% of patients, and 18.8% had suboptimal levels (20-30 ng/mL).

Conclusions:

• Both rheumatoid arthritis pharmacotherapy and seasonal factors significantly influence serum 25-hydroxy vitamin D levels in patients.
• Leflunomide may be associated with better vitamin D status compared to methotrexate, particularly during summer months.
• The high prevalence of vitamin D deficiency/insufficiency highlights the need for monitoring and management in RA patients.