Long-term effects of combined super high-flux and medium-flux dialysis on middle-molecule levels and sleep quality in maintenance hemodialysis: a prospective longitudinal cohort study

Abstract Background Super high-flux (SHF) dialyzers enhance the clearance of middle-molecule solutes, but their long-term use is often limited by cost and availability. This study evaluated the effects of combined SHF and medium-flux (MF) dialyzers on middle-molecule levels and sleep quality in patients undergoing maintenance hemodialysis (MHD). Methods A prospective longitudinal cohort study was conducted in 60 MHD patients (30 combined SHF–MF and 30 MF alone). The combined SHF–MF group received six SHF (Elisio HX19, Nipro, Japan) and six MF (Elisio 17 M, Nipro, Japan) sessions monthly, whereas the MF-alone group received 12 MF sessions. Predialysis hematological parameters and middle-molecule concentrations were measured quarterly, while sleep quality and pruritus were evaluated at baseline and at study completion using the Pittsburgh Sleep Quality Index (PSQI) and the 5-D Itch Scale. Multivariate linear mixed-effects models were applied to examine longitudinal changes and between-group differences across time points. Results The overall mean age was 55.0 ± 15.2 years, and 60% were male. β2-microglobulin (β2M) levels tended to be lower in the combined SHF–MF group than in the MF-alone group at 6 months ( β = −6.83, 95% CI: −10.46 to −3.20, p < 0.001) and 9 months ( β = −3.64, 95% CI: −7.20 to −0.08, p = 0.045). At 9 months, combined SHF–MF dialyzers were associated with lower PSQI scores ( β = −2.43, 95% CI: −4.53 to −0.34, p = 0.027). In contrast, the 5-D Itch Scale did not differ significantly between groups over time. No significant longitudinal changes were observed in parathyroid hormone levels or hematological parameters. Conclusions Combined SHF–MF dialyzers were associated with lower β2M levels and better sleep quality (lower PSQI scores) in MHD patients, suggesting a feasible approach for resource-limited settings.