Serum vitamin D status inversely associates with a prevalence of severe sarcopenia among female patients with rheumatoid arthritis.

Sarcopenia is an age-related disease with an increased risk of mortality. It is emerging that low serum 25-hydroxyvitamin D [25(OH)D] affects the sarcopenic state in general, but in rheumatoid arthritis (RA), these associations are not understood although the prevalence of vitamin D insufficiency is high in RA. We conducted a cross-sectional study of older female outpatients from our cohort (KURAMA) database. We measured skeletal muscle mass, handgrip strength, and gait-speed to diagnose severe sarcopenia. The serum 25(OH)D concentration was measured using electrochemiluminescence immunoassay. A total of 156 female patients with RA (sarcopenia:44.9%, severe sarcopenia: 29.5%, and without sarcopenia: 25.6%) were enrolled. Classification of vitamin D status at a cutoff point of median 25(OH)D concentration revealed that low 25(OH)D status was associated with a high prevalence of severe sarcopenia and with low measured values of muscle mass, handgrip, and gait speed. Furthermore, multivariable logistic regression analysis identified that low 25(OH)D status was associated with a high prevalence of severe sarcopenia (OR 6.00; 95% CI 1.99-18.08).The same association was observed when the cut-off value was set at 20 ng/ml. In components of sarcopenia, both low physical performance and muscle mass were associated with low 25(OH)D status. In conclusion, vitamin D status was inversely associated with severe sarcopenia, low physical performance, and low skeletal muscle mass. Modification of vitamin D status including vitamin D supplementation should be investigated as a therapeutic strategy for sarcopenic patients with RA.

Urinary sodium-to-potassium ratio associates with hypertension and current disease activity in patients with rheumatoid arthritis: a cross-sectional study.

BACKGROUND: Excessive salt intake is thought to exacerbate both development of hypertension and autoimmune diseases in animal models, but the clinical impact of excessive salt in rheumatoid arthritis (RA) patients is still unknown. We performed a cross-sectional study to clarify the associations between salt load index (urinary sodium-to-potassium ratio (Na/K ratio)), current disease activity, and hypertension in an RA population. METHODS: Three hundred thirty-six participants from our cohort database (KURAMA) were enrolled. We used the spot urine Na/K ratio as a simplified index of salt loading and used the 28-Joint RA Disease Activity Score (DAS28-ESR) as an indicator of current RA disease activity. Using these indicators, we evaluated statistical associations between urinary Na/K ratio, DAS28-ESR, and prevalence of hypertension. RESULTS: Urinary Na/K ratio was positively associated with measured systolic and diastolic blood pressure and also with prevalence of hypertension even after covariate adjustment (OR 1.34, p <  0.001). In addition, increased urinary Na/K ratio was significantly and positively correlated with DAS28-ESR in multiple regression analysis (estimate 0.12, p <  0.001), as was also the case in gender-separated and prednisolone-separated sub-analyses. CONCLUSION: Urinary Na/K ratio was independently associated with current disease activity as well as with prevalence of hypertension in RA patients. Thus, dietary modifications such as salt restriction and potassium supplementation should be investigated as a potential candidate for attenuating both disease activity and hypertension in RA patients.