Prolonged-hours hemodialysis is related to decrease mortality threat in sufferers with end-stage renal illness

Results from the Dialysis Outcomes and Practice Patterns Study
February 19, 2021 0 Comments


Prolonged-hours hemodialysis gives considerably longer remedy time in comparison with standard hemodialysis schedules and is related to improved fluid and electrolyte management and favorable cardiac reworking. Nevertheless, whether or not extended-hours hemodialysis improves survival stays unclear. Due to this fact, we decided the affiliation between extended-hours in comparison with standard hemodialysis and the danger of all-cause mortality in a nationally consultant cohort of sufferers initiating upkeep dialysis in the USA from 2007 to 2011. Survival analyses utilizing causal inference modeling with marginal structural fashions had been carried out to check mortality threat amongst 1,206 people present process thrice weekly extended-hours hemodialysis or 111,707 sufferers receiving standard hemodialysis therapies. The typical remedy time per session for extended-hours hemodialysis was 399 minutes in comparison with 211 minutes for standard remedy. The crude mortality charge with extended-hours hemodialysis was 6.4 deaths per 100 patient-years in contrast with 14.7 deaths per 100 patient-years for standard hemodialysis. Within the major evaluation, sufferers handled with extended-hours hemodialysis had a 33% decrease adjusted threat of demise in comparison with those that had been handled with a standard routine (95% confidence interval: 7% to 51%). Further analyses accounting for analytical assumptions concerning publicity and end result, facility-level confounders, and prior modality historical past had been related. Thus, on this giant nationally consultant cohort, remedy with extended-hours hemodialysis was related to a decrease threat for mortality in comparison with remedy with standard in-center remedy. Adequately powered randomized medical trials evaluating extended-hours to standard hemodialysis are required to verify these findings.

Key phrases: end-stage renal illness, upkeep dialysis, in-center hemodialysis, nocturnal hemodialysis, extended-hours hemodialysis, mortality threat


Though the previous decade has witnessed a modest enchancment in survival for sufferers present process upkeep dialysis in the USA, mortality continues to be unacceptably excessive, approaching 20 % per 12 months.1 Whereas early observational research urged {that a} larger delivered dose of dialysis could also be related to improved medical outcomes, a profit of accelerating the dialysis dose above at the moment accepted requirements has not been confirmed by randomized managed medical trial outcomes.2–4 This has prompted a seek for different modifiable dialysis parameters, together with dialysis modality and remedy time, so as to enhance long-term medical outcomes. In line with this emphasis, the Institute of Medication in the USA has recognized comparative effectiveness of dialysis therapies as the one kidney disease-related subject among the many prime 100 nationwide priorities for comparative effectiveness analysis.5

Quite a few observational research over the previous twenty years have demonstrated that shorter remedy instances with standard hemodialysis are related to larger mortality.6–10 Not too long ago, an growing variety of sufferers are being handled with extended-hours hemodialysis consisting of considerably longer remedy instances, which has been related in observational research with decrease hospitalization charges and enhancements in metabolic parameters, left ventricular mass and hypertension.11–14 Nevertheless, there are restricted knowledge on the affiliation of extended-hours hemodialysis with affected person survival, as prior research have been small or single-center investigations, or haven’t addressed the a number of time-varying and facility-level elements which may trigger confounding.15–19

Randomized managed trials stay the gold normal for comparative effectiveness analysis. Nevertheless, trials which have sought to randomly assign sufferers to certainly one of two completely different dialysis modalities have encountered substantial challenges in enrolling the goal variety of sufferers.20–22 These challenges seemingly replicate that almost all sufferers are usually not keen to depart the collection of dialysis modality to random task if the therapies have substantial and extensively differing results on life-style, schedule, and weekly dedication to dialysis-related remedy.22 Moreover, no up to date randomized managed trial has sought to check the impact of prolonged hemodialysis remedy time unbiased of elevated remedy frequency. Observational research utilizing up to date causal inference modeling akin to marginal structural fashions make the most of strong statistical instruments that deal with time-varying exposures and confounding, and thus characterize an essential various technique for investigating the comparative effectiveness of dialysis modalities.23 On this research, we used marginal structural modelling to deal with the speculation that extended-hours hemodialysis is related to decrease threat for all-cause demise in comparison with standard hemodialysis.


Examine Cohort

The research pattern comprised 136,207 people with end-stage renal illness who initiated upkeep dialysis from 2007 to 2011 handled in dialysis amenities operated by a big US dialysis supplier (). In comparison with people handled solely with standard hemodialysis (n=111,707), sufferers categorized as handled with extended-hours hemodialysis for a number of 91-day intervals (n=1,206) had been youthful, extra more likely to be male, black, have diabetes or comorbid heart problems, have major insurance coverage apart from Medicare or Medicaid, and to dwell within the western area of the US (). Different sufferers, who had been by no means handled with extended-hours hemodialysis and had been handled with no less than one modality apart from standard hemodialysis, differed from each extended-hours and solely standard hemodialysis sufferers (). Nevertheless, within the first 91-day interval of dialysis, laboratory and remedy parameters had been related amongst sufferers ever handled with extended-hours hemodialysis, sufferers solely handled with standard hemodialysis, and different sufferers ().

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Building of the research cohort

Desk 1

Affected person traits at the beginning of the primary 91-day dialysis remedy interval after initiation of dialysis, by modality, and whole proportion of variables with lacking info.

Ever handled with
Solely handled
% Lacking
Age, years 0
  18–24 3 1 2
  25–44 28 11 18
  45–59 42 27 30
  60–74 24 36 33
  ≥75 3 24 16
Race, % 0
  Asian 3 3 4
  Black 37 31 21
  White 47 47 58
  Hispanic 10 15 13
  Different 3 4 3
Male, % 70 57 56 0
Main Well being Insurance coverage,% 0
  Medicare 35 53 46
  Medicaid 7 7 5
  Different insurance coverage 58 40 48
Geographic Location 0
  Northeast, % 9 13 12
  Midwest, % 30 18 19
  West, % 40 25 41
  South, % 21 44 28
Yr of Incidence 0
  2007 25 20 20
  2008 24 20 21
  2009 24 21 22
  2010 18 21 22
  2011 9 18 15
Co-existing sicknesses, % 0
  Atherosclerotic Coronary heart
21 14 18
  Congestive Coronary heart Failure 55 37 30
  Diabetes 68 58 63
  Different Cardiovascular 19 15 16
Entry Sort, %a 6.5
  Arteriovenous fistula or
24 20 11
  Central venous catheter 73 80 46
  Peritoneal dialysis
3 0 42
Remedy parametersa
  Physique mass index 32.5±9.5 28.2±7.4 28.3±7.2 8.7
  Pre-dialysis systolic blood
  stress, mm Hg
152±18 147±19 148±19 5.9
  Weekday inter-dialytic
  weight achieve, %
2.2 [1.5,3.0] 2.3 [1.5,3.2] 0.02 [0.013, 0.029] 9.3
  Weekend inter-dialytic
  weight achieve, %
2.8 [2.0,4.1] 3.1 [2.1, 4.2] 0.027 [0.017, 0.038] 8.9
Laboratory Variables
  Serum albumin, g/dL 3.6±0.5 3.5±0.5 3.6±0.5 1.6
  Alkaline phosphatase,
87 [69, 111] 87 [69, 115] 82 [65, 106] 1.8
  Serum calcium, mg/dL 9.1±0.6 9.1±0.6 9.1±0.6 1.5
  Serum ferritin, ng/mL 234 [138, 373] 282 [164, 484] 237 [133, 413] 2.8
  Hemoglobin, g/dL* 11.1±1.2 11.1±1.2 11.3±1.2 1.3
  Serum iron saturation, % 21 [17,25] 22 [17, 27] 23 [18, 29] 2.1
  Parathyroid hormone,
378 [240, 569] 314 [197, 486] 294 [183, 470] 2.0
  Serum phosphorous,
5.3±1.2 4.9±1.2 4.9±1.1 1.5
  spKt/V urea 1.4 [1.2, 1.8] 1.6 [1.4, 1.8] 1.4 [1.2, 1.7] 8.2
Parenteral drugs
  Cumulative iron,
1062 [525,1600] 1000 [400, 1400] 400 [0, 1050] 0
  Erythropoietin Dose,
  median items/week
[16,500, 36,300]
[13,200, 33,000]
[9,000, 29,700]

Sufferers who initiated extended-hours hemodialysis following a number of 91-day intervals of standard hemodialysis had larger serum alkaline phosphatase, ferritin, parathyroid hormone, spKt/V, and decrease serum phosphorous, cumulative iron dose (prescribed over every 91-day interval), and median erythropoietin dose throughout remedy with extended-hours hemodialysis in comparison with values throughout remedy with standard hemodialysis previous to switch (Supplemental Desk S1).

The typical delivered remedy time per session with extended-hours hemodialysis was 399 ± 64 minutes in comparison with 211 ± 27 minutes with standard hemodialysis (intra-patient coefficient of variation 10.8% and 6.8%, respectively) (). Remedy frequency was related amongst sufferers handled with extended-hours hemodialysis (2.8 therapies per week, interquartile vary [IQR 2.4, 2.9]) and standard hemodialysis (2.9 therapies per week, [IQR 2.7, 2.9]). Amongst extended-hours hemodialysis sufferers, extended-hours hemodialysis was the preliminary dialysis modality for 353 sufferers (29%); 823 (67.5%) began dialysis with standard hemodialysis, 37 (3%) began with peritoneal dialysis, and 6 (0.5%) initiated with house hemodialysis or in-center hemodialysis lower than 3 instances per week. Total, median time from initiation of dialysis to start out of remedy with extended-hours hemodialysis was 6.7 months (IQR 1.0, 19.2). The median length between initiation of hemodialysis and switch to a different modality, censoring, or demise was 7.6 months (IQR 2.3, 17.6) for standard hemodialysis and seven.2 months (IQR 3.4, 15.1) for extended-hours hemodialysis. Of sufferers handled with extended-hours hemodialysis, 535 (44%) transferred to a different dialysis modality for a number of 91 day intervals. Of those sufferers, none died and 78 had been censored (66 resulting from finish of follow-up) inside 91 days of switch from extended-hours hemodialysis. Of sufferers handled with standard hemodialysis, 10% later transferred to a different modality.

Prolonged-hours Hemodialysis and All-Trigger Mortality

In whole, 82 sufferers died throughout a 91-day interval during which they had been receiving extended-hours hemodialysis, in comparison with 29,778 deaths during times of standard hemodialysis. Crude mortality charges had been 6.4 and 14.7 deaths per 100 patient-years for extended-hours and standard hemodialysis, respectively (). Adjusted for remedy historical past and time-varying laboratory and remedy parameters utilizing marginal structural fashions, in addition to for case-mix elements, sufferers handled with extended-hours hemodialysis had a 33% decrease adjusted threat of demise in comparison with these handled with standard hemodialysis (95% confidence interval [95% CI] 7% to 51% decrease) ().

Desk 2

Dangers for all-cause mortality evaluating extended-hours hemodialysis to standard hemodialysis, by time interval for dialysis modality demise attribution

Demise Attribution Hemodialysis
Variety of
Affected person-years of
Hazard Ratiob
(95% CI)
Present dialysis
modality at time
of demisec
Prolonged-hours 82 1,279 6.4 0.67
(0.49, 0.93)
Typical 29,796 203,046 14.7
Dialysis modality
of 91-day interval
previous to demised
Prolonged-hours 82 1,279 6.4 0.68
(0.49, 0.93)
Typical 29,692 203,028 14.6
for all occasions after
Prolonged-hours 126 1,865 6.8 0.62
(0.47, 0.81)
Typical 29,761 202,582 14.7

Attributing deaths to the dialysis modality 90 days previous to demise didn’t meaningfully change the danger estimate (). An excessive method—attributing all deaths following initiation of extended-hours hemodialysis to extended-hours hemodialysis, whatever the precise modality on the time of demise—elevated the variety of deaths attributed to extended-hours hemodialysis to 126, however the threat ratio between extended-hours and standard hemodialysis didn’t change considerably (HR 0.62 [0.47 to 0.81]. ().

Beginning follow-up from the 91st day following begin of dialysis, additional adjustment for vascular entry sort, or proscribing the cohort to sufferers for whom extended-hours dialysis remedy was most probably to be out there didn’t meaningfully change hazard ratio estimates (). Moreover, outcomes of analyses amongst a restricted cohort that excluded sufferers who by no means initiated extended-hours hemodialysis, however to whom extended-hours hemodialysis was out there, had been related (). Outcomes from a matched evaluation during which every affected person ever-treated with extended-hour hemodialysis was matched with as much as 20 different sufferers who had the identical dialysis modality remedy historical past previous to initiation of extended-hours hemodialysis, weren’t considerably completely different (). Lastly, in interplay analyses, no proof of impact modification by age, intercourse, or race was discovered (P>0.2 for every).

Desk 3

Outcomes of research with various assumptions: Dangers for all-cause mortality evaluating extended-hours hemodialysis to standard hemodialysis.

Evaluation Prolonged-hours
95% CI

Deaths Affected person-years Deaths Affected person-years
Starting evaluation 91
days after dialysis
82 1,202 29,654 176,508 0.67 (0.47, 0.94)
Together with solely sufferers
with entry to extended-
hours hemodialysisb
82 1,279 11,643 76,980 0.68 (0.50, 0.93)
Excluding sufferers who
by no means initiated extended-
hours hemodialysis, however
to whom it was out there
82 1,279 18,656 122,334 0.67 (0.49, 0.91)
Further adjustment
for vascular entry
82 1,279 29,796 203, 046 0.69 (0.50, 0.95)
Matched cohortc 73 1470 2,041 17,717 0.58 (0.43, 0.79)


Utilizing up to date causal inference strategies on this giant research of incident dialysis sufferers, we discovered that remedy with three times-weekly extended-hours hemodialysis was related to 34% decrease threat for demise in contrast with standard hemodialysis. Our outcomes had been strong, with constant remedy impact estimates in a number of sensitivity analyses accounting for temporal assumptions concerning publicity and end result, facility-level confounders associated to the provision of extended-hours hemodialysis to sufferers, and prior modality historical past. To our information, that is the most important research of extended-hours hemodialysis reported.

The previous decade has seen a resurgent curiosity in exploring the advantage of extra frequent and/or longer dialysis therapies. Culleton et al.24 randomly assigned 52 sufferers in Canada to 3 times-weekly in-center or house hemodialysis versus six times-weekly nocturnal hemodialysis, and located that the latter remedy resulted in a lower in left ventricular mass and systolic blood stress, and a discount in serum phosphorus and parathyroid hormone ranges. The Frequent Hemodialysis Community (FHN) nocturnal trial in contrast standard three times-weekly hemodialysis carried out at house with frequent house nocturnal hemodialysis carried out six times-weekly for ≥6 hours per session, and confirmed that frequent nocturnal remedy resulted in decrease blood stress and reductions in serum phosphorus.21 Surprisingly, long-term follow-up of sufferers enrolled within the FHN nocturnal trial discovered an elevated threat for demise within the nocturnal dialysis group, though warning must be exercised in interpretation of those outcomes given an unexpectedly low mortality charge noticed within the standard dialysis group and excessive charges of dialysis modality switches on this research.25 Of word, these two trials assessed the influence of accelerating each hemodialysis remedy time and remedy frequency collectively and thus didn’t enable for evaluation of the unbiased impact of adjusting remedy time. Within the not too long ago reported ACTIVE Dialysis Trial, extending hemodialysis hours to a goal of ≥ 24 hours weekly in comparison with normal dialysis hours (12–15 hours weekly) resulted in reductions in serum phosphorus and blood stress remedy necessities.26 Nevertheless, just like the aforementioned FHN and Canadian trials of nocturnal hemodialysis, the intervention in ACTIVE was not designed to evaluate the unbiased influence of extending hemodialysis remedy instances separate from modifications in remedy frequency.27 In distinction, the Time to Scale back Mortality in Finish-Stage Renal Illness (TiME) trial is an ongoing pragmatic randomized medical trial designed to check the speculation that three times-weekly hemodialysis with session durations of no less than 4.25 hours improves mortality, hospitalization, and health-related quality-of-life in comparison with common care consisting of therapies with imply length of three.5 hours.28 Nevertheless, given this comparatively small improve in remedy time for the intervention group in comparison with the marked variations in remedy time achieved with extended-hours hemodialysis, the outcomes of the TiME trial is not going to immediately deal with the influence of extended-hours hemodialysis on medical outcomes.

In our research, sufferers handled with extended-hours hemodialysis had common remedy instances that exceeded these of standard hemodialysis by greater than 3 hours. This substantial lengthening of the hemodialysis remedy is way higher than what is feasible to realize throughout the context of standard in-center hemodialysis or extra frequent hemodialysis, whether or not carried out in-center or at house. There are a variety of potential mechanisms by which such considerably longer hemodialysis therapies could result in improved medical outcomes, unbiased of any improve in dialysis frequency. Nocturnal extended-hours hemodialysis has been proven to reinforce phosphorus removing and scale back arterial stiffness, potential mediators within the pathway between finish stage renal illness and medical cardiovascular occasions.7,29,30 Certainly, in our research, we discovered that for sufferers who switched from standard in-center hemodialysis to extended-hours hemodialysis, serum phosphorus ranges declined into the vary related to decrease threat for demise in prior observational research.31 Prior randomized trials evaluating extended-hours to plain size hemodialysis remedy have proven decrease pre-dialysis serum phosphorus in sufferers assigned to extended-hours therapies, although such trials have additionally included elevated dialysis frequency within the intensive remedy arm, stopping dedication of the unbiased impact of dialysis length.24,32 Along with its influence on markers of mineral and bone illness, one of many main benefits of extended-hours hemodialysis is that longer remedy instances facilitate a slower internet fluid removing charge, which has been proven to be related to decrease systemic blood stress and diminished cardiovascular morbidity and mortality.6,33 Prior randomized trials of elevated dialysis frequency both with or with out elevated dialysis length have demonstrated decrease pre-dialysis systolic blood pressures amongst affected person assigned to intensive dialysis therapies.32,34 Sadly, as with markers of mineral metabolism, there’s a paucity of information from medical trials on the influence of thrice-weekly extended-hours hemodialysis on medical quantity overload or blood stress. Prior research have demonstrated an affiliation amongst conversion to extended-hours hemodialysis, regression of left ventricular mass, and enchancment in myocardial mechanics and cardiomyocyte gene expression, that are all seemingly contributors to improved cardiovascular outcomes.35,36 One essential profit doubtlessly favoring thrice-weekly extended-hours hemodialysis over different types of dialysis intensification is avoidance of the necessity for extra frequent use of the affected person’s vascular entry. Within the FHN trials, sufferers present process extra frequent hemodialysis had been extra more likely to have problems associated to vascular entry in comparison with sufferers present process standard hemodialysis.32,34 In distinction, there is no such thing as a proof that thrice-weekly extended-hours hemodialysis is related to a rise in access-related problems in comparison with standard remedy, though no knowledge from adequately powered medical trials can be found.

We discovered a >30% discount within the threat for demise related to extended-hours hemodialysis in our research. As a result of potential presence of residual confounding from unmeasured affected person and treatment-related elements in an observational cohort research, the precise good thing about extended-hours hemodialysis could also be smaller than this estimate. Lacson et al.17 have beforehand proven a 25% discount in threat for demise related to conversion from standard hemodialysis to nocturnal in-center hemodialysis in a propensity score-matched observational evaluation. Lengthy-term follow-up of sufferers from the FHN Each day Trial demonstrated a persistent 46% discount in threat for demise for sufferers randomized to frequent hemodialysis, despite the fact that the vast majority of such sufferers returned to standard thrice-weekly remedy on the conclusion of the preliminary 12-month intervention interval.37 Such outcomes counsel that even short-term modifications within the provision of dialysis remedy, akin to remedy with extended-hours hemodialysis, have the potential to lead to lasting profit.

Our findings lengthen these of prior observational research by means of numerous essential strengths in research design and method. First, our examination of the most important cohort of sufferers present process extended-hours hemodialysis maximizes statistical energy and precision in estimates of remedy impact in comparison with prior research.15–18 Second, we noticed a big distinction within the imply and general distribution of delivered remedy instances between sufferers present process standard versus extended-hours hemodialysis, which reinforces our capability to detect an affiliation between remedy time and outcomes. Third, our research permits an examination of the affiliation of longer dialysis remedy time with outcomes unbiased of elevated remedy frequency by evaluating in-center extended-hours versus standard hemodialysis, each delivered 3 times weekly. Fourth, we used a up to date marginal structural modelling method to maximise our capability to account for time-varying exposures and confounders. Use of marginal structural fashions additionally immediately accounts for between-group variations in time since initiation of dialysis, addressing the propensity of more healthy sufferers to outlive to switch to extended-hours hemodialysis. Lastly, we confirmed the consistency of our findings throughout many secondary and sensitivity analyses to make sure robustness of our remedy impact estimates.

Regardless of its strengths, our research additionally has limitations. Sufferers present process remedy with extended-hours hemodialysis are more likely to differ in essential methods from sufferers present process standard hemodialysis, together with attributes akin to train capability, cardiovascular perform, social assist buildings, cognitive perform, and motivation that aren’t captured in out there knowledge. Moreover, we weren’t capable of account in our analyses for the total vary of affected person coexisting sicknesses which can differ in prevalence amongst sufferers present process extended-hours versus standard hemodialysis and in addition influence mortality threat. Though we integrated a lot of demographic and laboratory predictors into the event of the marginal structural fashions, it’s seemingly that residual confounding by unmeasured traits stays, and such confounding could also be partly accountable for the noticed remedy results. Though we had been capable of look at the affect of facility stage practices in sensitivity analyses, we had been unable to account for physician-level practices. Physicians offering extended-hours hemodialysis could differ systematically from those that don’t with respect to care pathways and high quality, and this can be an extra supply of residual confounding. Lastly, over 40% of sufferers handled with extended-hours hemodialysis in our research subsequently transferred to a different dialysis modality for no less than one 91-day interval. We didn’t discover that transfers from extended-hours hemodialysis had been adopted by a excessive mortality charge on the next modality, and certainly we noticed that no affected person who transferred from extended-hours hemodialysis died inside 91-days of switch. Nevertheless, additional research are wanted to analyze causes and threat elements for transfers from extended-hours dialysis hemodialysis, as such attrition could pose a problem to large-scale utility of extended-hours dialysis therapies.

In conclusion, in a big observational cohort research, we demonstrated that remedy with extended-hours hemodialysis is related to roughly one-third decrease threat for demise in comparison with standard hemodialysis. Given the inherent limitations of observational research in definitively figuring out causation, there’s a thus a necessity for well-designed randomized medical trials to check whether or not task of sufferers to remedy with extended-hours hemodialysis ends in enchancment in patient-centered medical outcomes together with not solely mortality and hospitalization, but additionally affected person autonomy, care burden and satisfaction, and health-related high quality of life. To achieve success and to finally influence medical observe, future trials will should be rigorously designed to deal with boundaries to affected person enrollment given the substantial recruitment challenges noticed in prior randomized research testing the comparative effectiveness of dialysis modalities on affected person outcomes.


Examine Inhabitants and Information Supply

The research cohort comprised all sufferers age 18 years or older who began upkeep dialysis in calendar years 2007 by means of 2011, and obtained remedy for no less than 60 days at a facility operated by DaVita Inc. (N=162,664). Exclusion of sufferers with fewer than 60 days whole dialysis remedy is frequent observe in analyses of dialysis cohorts.19 Sufferers and not using a dialysis remedy session at a collaborating facility inside 91 days of ESRD incidence had been excluded (N=24,940), as had been sufferers lacking info on race (N=1,517), leading to a last cohort of 136,207 sufferers (). All knowledge had been obtained from dialysis facility digital medical data. All laboratory values had been measured utilizing standardized automated strategies in a central laboratory (Deland, FL) inside 24 hours of blood assortment. Coexisting sicknesses had been coded as prevalent in the event that they had been recorded at any time throughout follow-up.

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Distribution of imply remedy time per session over every 91-day interval, for standard hemodialysis (darkish bars, 899,696 patient-periods) or extended-hours hemodialysis (mild bars, 5,610 patient-periods)

For readability one outlier with imply remedy time 693 minutes was omitted from the conventional-hours group. Three % of values plotted had been imputed with a number of imputation. Bin width is 10 minutes.

Modality was categorized as certainly one of six: both standard thrice-weekly hemodialysis, extended-hours hemodialysis, peritoneal dialysis, house hemodialysis, extra frequent in-center hemodialysis (>3 instances/week), or much less frequent in-center hemodialysis (<3 instances/week).19 Task to extended-hours hemodialysis for the current analyses was based mostly on dialysis facility remedy data which recognized sufferers as having obtained nocturnal in-center hemodialysis; these sufferers had been handled in a single day in-center three times-weekly whereas sleeping. To categorise the dialysis modalities obtained by a affected person over time, particular person dialysis session data had been analyzed for the date and modality of remedy administered. Subsequent to the primary modality recorded, every affected person was thought of to have switched to a unique modality if she or he was handled solely with that modality over a interval of least 60 consecutive days, a rule generally utilized for analyzing comparative effectiveness of dialysis modalities.1 Therefore, every affected person’s document was divided into remedy intervals by modality, every interval after the primary lasting no less than 60 days until the affected person died or was censored.

Subsequent, the follow-up interval for every affected person was divided into successive 91-day intervals from the date of first dialysis; follow-up was out there for as much as 20 intervals. The modality assigned for every 91-day interval was that with which the affected person was handled for >45 days in that interval; nevertheless, for the 91-day interval during which the affected person was censored or died, the modality obtained for the longest interval was assigned. Vascular or peritoneal entry was assigned to every 91-day interval in an identical method. Every 91-day interval was assigned the imply of recorded laboratory and medical measurements through the interval. Facility was assigned as the ability at which the affected person obtained probably the most dialysis periods in a 91-day interval.

All-cause mortality was outlined by date of demise through the follow-up interval (January 1, 2007–December 31, 2011). Censoring causes included kidney transplant, switch to a facility operated by one other dialysis supplier, discontinuation of dialysis, and administrative finish of follow-up. The Institutional Overview Boards on the Los Angeles Biomedical Analysis Institute and the College of Washington accepted the research as exempt from knowledgeable consent.

Statistical Analyses

For an outline of variations between sufferers in line with dialysis modality, descriptive statistics had been calculated for the primary 91-day interval of dialysis (baseline) for the mutually unique teams of sufferers ever handled with extended-hours hemodialysis (N=1,206), sufferers handled solely with standard hemodialysis (N=111,707), and different sufferers (N=23,294).

The extent of lacking knowledge was examined at baseline and in subsequent 91-day intervals. At baseline, the extent of lacking knowledge diverse from roughly 9% for physique weight measurements and eight% for single-pool urea Kt/V (spKt/V), to 1–2% for many serum and urinary measurements (e.g., albumin, serum alkaline phosphatase, serum calcium) (). Total, roughly 25% of sufferers had been lacking info on a number of laboratory or medical measurements for a number of 91-day interval. Due to this fact, complete-case evaluation would have deleted a considerable portion of sufferers; lacking info for time-varying covariates was imputed utilizing a number of imputation with ten repetitions. The a number of imputation mannequin included all kinds of laboratory and medical measurements, case-mix variables, facility variables, dialysis modality, the estimated Nelson-Aalen cumulative hazard of mortality, an indicator of demise or explanation for censoring, and the overall time for every affected person beneath remark (see Detailed Statistical Strategies out there in Supplementary Appendix).38

For the first evaluation, the impact of remedy with extended-hours hemodialysis in comparison with standard hemodialysis on all-cause mortality was assessed utilizing marginal structural fashions, with dialysis modality handled as a time-varying publicity.23 Hazard ratio estimates from these fashions have the interpretation because the ratio of the mortality charges evaluating cohorts handled with extended-hours versus standard hemodialysis, and with the identical prior remedy historical past and different covariates. A time-varying publicity method was utilized to maximise accuracy of occasion attribution and decrease threat of immortal time bias (Detailed Statistical Strategies out there in Supplementary Appendix).39 Marginal structural fashions using time-varying exposures have been proven to be legitimate even when the publicity of curiosity modifications a number of instances over follow-up.40,41

To assemble the fashions, stabilized inverse likelihood of remedy weights (SIPTW) and stabilized inverse likelihood of censoring weights (SIPCW) had been computed for every 91-day interval to account for historical past of prior dialysis modality remedy and different potential time-varying confounders (see Supplemental Strategies).23,42 The potential confounders used to individually estimate SIPTWs and SIPCWs included case-mix and demographic variables, dialysis modality from the instantly previous 91-day interval, a wide range of time-varying laboratory and medical measures, and facility-level variables. The ultimate mixed stabilized inverse likelihood weights had been estimated by multiplying the SIPTW and SIPCW.

Lastly, a Cox proportional hazards fashions weighted by the stabilized inverse likelihood weights was match evaluating hazard of mortality whereas handled with extended-hours dialysis to standard hemodialysis (reference), adjusted for age, gender, race, sort of insurance coverage, diabetes, congestive coronary heart failure, atherosclerotic coronary heart illness, different cardiovascular sickness, and 12 months of dialysis incidence. Laboratory and different time-varying intermediate variables weren’t included as adjustment covariates within the last Cox mannequin.

A number of sensitivity analyses had been carried out to analyze modeling assumptions. First, to evaluate the potential for delayed impact of modifications in dialysis modality, analyses had been repeated by attributing demise to the dialysis modality with which the affected person was handled within the 91-day interval previous to the interval during which demise occurred. Second, analyses had been repeated during which any demise following initiation of extended-hours dialysis was attributed to extended-hours dialysis, no matter whether or not the affected person had transferred from extended-hours dialysis. Third, to take away the fast influence of dialysis initiation, analyses had been carried out during which follow-up was began on the 91st day after initiation of dialysis. Fourth, to analyze the influence of further patient-level and facility-level variables that might decide availability and initiation of extended-hours dialysis, analyses had been carried out in a restricted cohort comprising sufferers who had been handled at a facility that had (1) handled any affected person with extended-hours hemodialysis or (2) handled any affected person who was handled with extended-hours dialysis at a unique facility. Moreover, analyses had been repeated in a second restricted cohort comprising sufferers who had been ever handled with extended-hours hemodialysis and sufferers solely handled with standard hemodialysis who had been handled at amenities the place extended-hours HD was unavailable. Fifth, analyses had been repeated on a matched cohort during which sufferers who had been handled with extended-hours hemodialysis had been matched with as much as 20 sufferers with similar dialysis remedy modality historical past in every 91-day interval previous to initiation of extended-hours dialysis (by the index affected person), 12 months of incidence, age, intercourse, race, underlying renal illness, Charlson index, and geographic area. The matched cohort evaluation was additionally restricted to sufferers to whom extended-hours remedy was out there as described above (Supplemental Strategies and Determine S1).

Impact modification was investigated by first repeating the marginal structural Cox mannequin evaluation estimating the affiliation of dialysis modality with mortality, inside strata of age, intercourse, and race. Subsequently, to conduct statistical testing of the interplay, the evaluation was repeated including a multiplicative interplay time period between dialysis modality and age, intercourse, or race to the marginal structural Cox mannequin.23

All analyses adopted the Strengthening the Reporting of Observational research in Epidemiology (STROBE) pointers.43 Additional element concerning statistical strategies, together with elimination of immortal time bias, is accessible within the Supplementary Materials. Analyses had been carried out with Stata 13.1 (Stata Corp, School Station, TX, USA

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