Hara T, et al. - In this prospective cohort study performed on hemodialysis (HD) patients, researchers examined the links between intra-dialytic alterations in hemoglobin concentration and cardiovascular events. This inquiry was based on the Japanese Dialysis Outcomes and Practice Pattern Study phases 4 and 5. The ratio of post-dialysis hemoglobin level to pre-dialysis hemoglobin level (post-Hb/pre-Hb) at baseline was calculated as the predictor. Of 865 patients enrolled, major adverse cardiovascular event (MACE) development was noted in 145 (16.8%) patients during a median observation period of 2.6 years. Based on baseline post-Hb/pre-Hb, they defined 4 groups of patients (< 1.0, ≥ 1.0 to < 1.1, ≥ 1.1 to < 1.2, and ≥ 1.2). In patients with post-Hb/pre-Hb ratios of < 1.0, ≥ 1.0 to < 1.1, and ≥ 1.2 vs the reference post-Hb/pre-Hb ratio of ≥ 1.1 to < 1.2, the estimated multivariable-adjusted HRs for MACEs were 1.69, 1.29, and 1.31, respectively. In patients undergoing HD, a high risk of MACEs was observed in correlation with high and low intra-dialytic changes in hemoglobin concentration.