In multivariate linear regression analysis for LOS with iron deficiency as a binary variable, iron deficiency remained an independent predictor of LOS in HFpEF (b = 2.74, 95% CI 0.32–5.17), after adjusting for CKD, CAD, hypertension, DM, obesity, atrial fibrillation or flutter, COPD, CRP, and age. This evidence concerns the gene CRP and atrial fibrillation.