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. 2010 Apr;77(7):630-6.
doi: 10.1038/ki.2009.523. Epub 2010 Jan 20.

Shorter Dialysis Times Are Associated With Higher Mortality Among Incident Hemodialysis Patients

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Free PMC article

Shorter Dialysis Times Are Associated With Higher Mortality Among Incident Hemodialysis Patients

Steven M Brunelli et al. Kidney Int. .
Free PMC article

Abstract

There is an association between hemodialysis session length and mortality independent of the effects of session duration on urea clearance. However, previous studies did not consider changes in session length over time nor did they control for the influence of time-dependent confounding. Using data from a national cohort of 8552 incident patients on thrice-weekly, in-center hemodialysis, we applied marginal structural analysis to determine the association between session length and mortality. Exposure was based on prescribed session length with the outcome being death from any cause. On the 31st day after initiating dialysis, the patients were considered at-risk and remained so until death, censoring, or completion of 1 year on dialysis. On primary marginal structural analysis, session lengths <4 h were associated with a 42% increase in mortality. Sensitivity analyses showed a dose-response relationship between session duration and mortality, and a consistency of findings across prespecified subgroups. Our study suggests that shorter hemodialysis sessions are associated with higher mortality when marginal structural analysis was used to adjust for time-dependent confounding. Further studies are needed to confirm these findings and determine causality.

Figures

Figure 1
Figure 1. Observed hemodialysis session lengths among study cohort
(a) Distribution of observed session length at baseline (n = 8552). (b) Representative transitions among strata of session length at baseline, months 3 and 6. At the start of at-risk time (at-risk day 0, corresponding to dialysis day 31), 2020 (23.6%) patients had session length ≤180 min; of these 303 (15.0%), 703 (34.8%), and 852 (42.2%) had session length of ≥240, 181–239, and ≤180 min, respectively, at the start of month 3; the remaining 162 (8.0%) had died or were censored by that time. Interpretation is analogous for other session-length strata and time intervals.
Figure 2
Figure 2. Hazard ratios (95% CIs) for all-cause mortality for shorter session length (<240 min) in baseline, time-updated, and marginal structural analyses
The referent category is session length ≥240 min (hazard ratio = 1 by definition; not shown). Gray bars represent unadjusted¼estimates. White bars represent estimates adjusted for age, sex, race (white versus nonwhite), vascular access (fistula, graft, catheter), body mass index (<20, 20–25, 25–30, and >30 kg/m2), congestive heart failure, eKt/V (≤1.0, 1.0–1.2, 1.2–1.4, 1.4–1.6, >1.6), systolic blood pressure, serum albumin, and creatinine. CI, confidence interval.
Figure 3
Figure 3. Adjusted hazard ratios (95% CIs) for all-cause mortality for shorter session length (<240 min) in prespecified subgroups
The referent category was session length ≥240 min. Estimates were adjusted through marginal structural analysis in an analogous manner to that used in the primary analysis; stabilized weights were reestimated for each subgroup. Baseline (B/l) eKt/V and congestive heart failure (CHF) refer to those values updated through dialysis day 30; baseline hospitalization refers to any hospitalization occurring between dialysis days 0–30.
Figure 4
Figure 4. Association between incremental decrements in session length and all-cause mortality
White bars represent session length ≤180 min, gray bars 181–239 min; the referent category was session length ≥240 min (hazard ratio = 1 by definition; not shown). Marginal structural analyses were adjusted for age, sex, race (white versus nonwhite), vascular access (fistula, graft, catheter), body mass index (≤20, 20–25, 25–30, >30 kg/m2), congestive heart failure, eKt/V (≤1.0, 1.0–1.2, 1.2–1.4, 1.4–1.6, >1.6), systolic blood pressure, serum albumin, and creatinine. MSM, marginal structural model.

Comment in

  • Importance of 3 h when dialyzing daily.
    Ayus JC, Achinger SG. Ayus JC, et al. Kidney Int. 2010 Oct;78(7):710; author reply 710-1. doi: 10.1038/ki.2010.248. Kidney Int. 2010. PMID: 20842154 No abstract available.

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