The Association Of Peripheral Iron Metabolism With Different Symptoms In Patients With Restless Legs Syndrome

Objective: To investigate the associations of peripheral iron status with RLS leg movements,severity,and outcomes.Methods: In this cross-sectional study,108 patients with RLS completed a semistructured questionnaire.Symtemic iron parameters(SIP)[serum ferritin,iron,and transferrin concentrations;unsaturated iron-binding capacity(UIBC)and total ironbinding capacity(TIBC);transferrin saturation] were measured following polysomnography(PSG).Data from patients with and without iron deficiency(ferritin concentration < 50 μg/L)were compared in crude analyses,and Spearman correlations of other iron indicators with RLS data were examined.An ordinal logistic regression model was used to adjust for confounders.Results: Ordinal logistic regression model showed SIP were not associated with most of leg movement parameters(P > 0.05)on PSG on univariate analysis.On multivariate analysis,ferritin deficiency was associated with five leg movement parameters,such as Periodic Limb Movements during Sleep(PLMS)index [odds ratio(OR)= 3.074;95 %confidence interval(CI),1.266-7.456;P = 0.013];UIBC was associated with three leg movement parameters,such as PLMS sequences index(OR =1.046;95 %CI,1.003-1.091;P = 0.035);TIBC was associated with five leg movement parameters,such as PLMS index(OR = 1.062;95 %CI,1.009-1.117;P = 0.022);serum transferrin concentration was associated with three leg movement parameters,such as duration of PLMS sequences(OR = 2.980;95 %CI,1.025-8.654;P = 0.045).Serum iron and transferrin saturation were not associated with any leg movement parameters(P > 0.05).On univariate analysis,SIP was not associated with the severity and most outcomes of RLS(P > 0.05)in ordinal logistic regression model.RLS severity and outcomes were not associated with ferritin deficiency or other peripheral iron indicators,except that daytime functioning assessed using the Pittsburg Sleep Quality Index was associated with TIBC(OR = 1.055;95 %CI,1.004-1.110;P = 0.036)on multivariate analysis.Conclusions: In this study,some SIP were associated mainly with leg movements,expecially for ferritin deficiency,UIBC,TIBC and serum transferrin concentration;rather than serum iron and transferrin saturation.SIP was not related with severity and most outcomes of RLS.