Longitudinal Outcomes Truncated by Death: Causal Estimands and Bayesian Estimators
Pith reviewed 2026-05-07 11:16 UTC · model grok-4.3
The pith
Stratified average causal effects combined with restricted mean survival time provide a more complete characterisation of treatment effects when death truncates longitudinal outcomes.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The main difficulty in defining causal estimands for longitudinal outcomes truncated by death arises from the lack of a natural notion of ordering and distance for such outcomes, which leads to an inherently multifactorial problem. Within a proposed framework that clarifies the challenges of censoring due to death, existing estimands are reviewed and the assumptions required for their identification and estimation are made explicit. Bayesian estimators are developed for each estimand and compared in a simulation study. Using data from a randomized controlled trial in amyotrophic lateral sclerosis, the stratified average causal effect combined with restricted mean survival time is shown to be
What carries the argument
A framework that makes explicit the assumptions required for identification of causal estimands in longitudinal settings with death truncation, highlighting the multifactorial character caused by absent ordering and distance for post-death outcomes and supporting the stratified average causal effect paired with restricted mean survival time.
Load-bearing premise
Outcomes truncated by death have no natural ordering or distance, turning the causal question into an inherently multifactorial problem that requires specific assumptions for any estimand to be identified.
What would settle it
A simulation or real dataset in which the combination of stratified average causal effect and restricted mean survival time fails to detect a clinically meaningful treatment difference that an alternative single estimand successfully captures under the same data-generating process.
read the original abstract
Defining a causal estimand for a longitudinal outcome truncated by death is challenging, because the outcome may be undefined at the end of follow-up. Although a range of estimands and several estimators have been proposed, guidance on the underlying causal assumptions and on the contexts in which each estimand is most appropriate remains limited. We propose a framework to clarify the challenges of defining causal estimands in a longitudinal setting with censoring due to death. Within this framework, we review existing estimands and make explicit the assumptions required for their identification and estimation. We develop Bayesian estimators for each estimand and compare their behavior in a simulation study. Finally, we illustrate the proposed approach using data from a randomized controlled trial in amyotrophic lateral sclerosis. We show that the main difficulty arises from the lack of a natural notion of ordering and distance for outcomes truncated by death. This leads to an inherently multifactorial problem. In this context, the stratified average causal effect, combined with restricted mean survival time, provides a more complete characterisation of treatment effects.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript proposes a framework for defining and estimating causal effects on longitudinal outcomes truncated by death. It reviews existing estimands, explicitly states the identification assumptions (sequential ignorability, positivity, consistency, and principal-stratum definitions), develops Bayesian estimators for each, compares their performance in a simulation study, and illustrates the approach with data from a randomized trial in amyotrophic lateral sclerosis. The central claim is that the lack of a natural ordering or distance metric for death-truncated outcomes makes the problem inherently multifactorial, so that the stratified average causal effect combined with restricted mean survival time supplies a more complete characterization of treatment effects than single-estimand alternatives.
Significance. If the framework and estimators hold, the work provides a useful clarification tool for a notoriously difficult area of causal inference. Explicitly stating assumptions for each estimand, supplying Bayesian estimators, and offering both simulation comparisons and a real-data ALS example adds practical value. The recommendation to combine SACE with RMST is grounded in the reviewed literature rather than a new identification result, and the illustrative nature of the simulation and trial analysis is appropriately scoped.
minor comments (3)
- The abstract states that assumptions are made explicit, but the main text should include a dedicated table or subsection that maps each reviewed estimand to its precise identifying assumptions for quick reference.
- In the simulation study, clarify the precise data-generating process and the range of sample sizes or censoring rates examined so that readers can assess how representative the reported estimator behavior is.
- Notation for principal strata and the definition of the stratified average causal effect should be introduced with a small illustrative example early in the methods section to aid readers unfamiliar with the principal-stratum approach.
Simulated Author's Rebuttal
We thank the referee for the positive and constructive review of our manuscript. The recommendation for minor revision is noted, and we will prepare a revised version addressing any editorial or minor points that may arise during the process.
Circularity Check
No significant circularity identified
full rationale
The paper reviews existing estimands for longitudinal outcomes truncated by death, explicitly states standard identification assumptions (sequential ignorability, positivity, consistency, and principal-stratum definitions), develops Bayesian estimators under those assumptions, and evaluates them via simulation study plus an ALS RCT illustration. The central recommendation—that the stratified average causal effect combined with restricted mean survival time supplies a more complete characterization—follows directly from the stated challenge of lacking natural ordering/distance for death-truncated outcomes, without any derivation step reducing to a fitted parameter, self-citation chain, or input-by-construction equivalence. The framework is presented as a clarification and review tool rather than a novel identification theorem, rendering the chain self-contained against external causal-inference benchmarks.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Standard causal assumptions required for identification of estimands in settings with death truncation
Reference graph
Works this paper leans on
-
[1]
Thomassen D, Roychoudhury S, Amdal CD, Reynders D, Musoro JZ, Sauerbrei W, et al. The role of the estimand frame- work in the analysis of patient-reported outcomes in single-arm trials: a case study in oncology. BMC Medical Research Methodology 2024 Nov;24(1):290.https://doi.org/10.1186/s12874-024-02408-x
-
[2]
Principal stratification in causal inference
Frangakis CE, Rubin DB. Principal stratification in causal inference. Biometrics 2002 Mar;58(1):21–29
2002
-
[3]
The Survival-incorporated Median vs the Median in the Survivors or in the Always-survivors: What Are We Measuring? And Why? Statistics in Medicine 2023 Dec;42(29):5479–5490
Xiang Q, Bosch RJ, Lok JJ. The Survival-incorporated Median vs the Median in the Survivors or in the Always-survivors: What Are We Measuring? And Why? Statistics in Medicine 2023 Dec;42(29):5479–5490
2023
-
[4]
Dong G, Huang B, Verbeeck J, Cui Y, Song J, Gamalo-Siebers M, et al. Win statistics (win ratio, win odds, and net benefit) can complement one another to show the strength of the treatment effect on time-to-event outcomes. Pharmaceutical Statistics 2023 Jan;22(1):20–33.https://onlinelibrary.wiley.com/doi/10.1002/pst.2251
-
[5]
Analysis of survival by tumor response
Anderson JR, Cain KC, Gelber RD. Analysis of survival by tumor response. Journal of Clinical Oncology: Official Journal of the American Society of Clinical Oncology 1983 Nov;1(11):710–719
1983
-
[6]
Joint Models for Longitudinal and Time-to-Event Data: With Applications in R
Rizopoulos D. Joint Models for Longitudinal and Time-to-Event Data: With Applications in R. New Y ork: Chapman and Hall/CRC; 2012
2012
-
[7]
(EMA) EMA, E9 (R1) Step 5 addendum on estimands and Sensitivity Analysis in Clinical T rials to the guideline on sta- tistical principles for clinical trials; 2020.https://www.ema.europa.eu/en/ich-e9-statistical-principles-clinical- trials-scientific-guideline
2020
-
[8]
arXiv; 2024.http://arxiv.org/abs/2309.06668, arXiv:2309.06668 [stat]
Carlin JB, Moreno-Betancur M, On the uses and abuses of regression models: a call for reform of statistical practice and teaching. arXiv; 2024.http://arxiv.org/abs/2309.06668, arXiv:2309.06668 [stat]. 20 Ortholand et al
-
[9]
Adjusting for Covariates in Randomized Clinical T rials for Drugs and Biological Products
FDA. Adjusting for Covariates in Randomized Clinical T rials for Drugs and Biological Products. FDA guidance document 2023
2023
-
[10]
The epidemiology of amyotrophic lateral sclerosis
T albott EO, Malek AM, Lacomis D. The epidemiology of amyotrophic lateral sclerosis. Handbook of Clinical Neurology 2016;138:225–238
2016
-
[11]
What does the ALSFRS-R really measure? A longitudinal and survival analysis of functional dimension subscores in amyotrophic lateral sclerosis
Rooney J, Burke T, Vajda A, Heverin M, Hardiman O. What does the ALSFRS-R really measure? A longitudinal and survival analysis of functional dimension subscores in amyotrophic lateral sclerosis. Journal of Neurology, Neurosurgery, and Psychiatry 2017 May;88(5):381–385
2017
-
[12]
ALS drug development guidances and trial guidelines
Andrews JA, Bruijn LI, Shefner JM. ALS drug development guidances and trial guidelines. Neurology 2019 Jul;93(2):66– 71.https://www.neurology.org/doi/10.1212/WNL.0000000000007695
-
[13]
The Combined Assessment of Function and Survival (CAFS): A new endpoint for ALS clinical trials
Berry JD, Miller R, Moore DH, Cudkowicz ME, Van Den Berg LH, Kerr DA, et al. The Combined Assessment of Function and Survival (CAFS): A new endpoint for ALS clinical trials. Amyotrophic Lateral Sclerosis and Frontotemporal Degener- ation 2013 Apr;14(3):162–168.https://doi.org/10.3109/21678421.2012.762930, publisher: T aylor & Francis _eprint: https:/ /doi...
-
[14]
Van Eijk RPA, Van Den Berg LH, Lu Y. Composite endpoint for ALS clinical trials based on patient preference: Patient- Ranked Order of Function (PROOF). Journal of Neurology, Neurosurgery & Psychiatry 2022 May;93(5):539–546.https: //jnnp.bmj.com/lookup/doi/10.1136/jnnp-2021-328194
-
[15]
Design and Statistical Innovations in a Platform T rial for Amyotrophic Lateral Sclerosis
Quintana M, Saville BR, Vestrucci M, Detry MA, Chibnik L, Shefner J, et al. Design and Statistical Innovations in a Platform T rial for Amyotrophic Lateral Sclerosis. Annals of Neurology 2023 Sep;94(3):547–560
2023
-
[16]
arXiv; 2023.http://arxiv.org/abs/2011.08047, arXiv:2011.08047 [stat]
Colnet B, Mayer I, Chen G, Dieng A, Li R, Varoquaux G, et al., Causal inference methods for combining randomized trials and observational studies: a review. arXiv; 2023.http://arxiv.org/abs/2011.08047, arXiv:2011.08047 [stat]
-
[17]
Causal Interpretation of the Hazard Ratio in Randomized Clinical T rials
Fay MP , Li F . Causal Interpretation of the Hazard Ratio in Randomized Clinical T rials. Clinical trials (London, England) 2024 Apr;21(5):623.https://pmc.ncbi.nlm.nih.gov/articles/PMC11502288/
2024
-
[18]
Utilizing the integrated difference of two survival functions to quantify the treatment contrast for designing, monitoring, and analyzing a comparative clinical study
Zhao L, Tian L, Uno H, Solomon SD, Pfeffer MA, Schindler JS, et al. Utilizing the integrated difference of two survival functions to quantify the treatment contrast for designing, monitoring, and analyzing a comparative clinical study. Clin- ical T rials (London, England) 2012 Oct;9(5):570–577
2012
-
[19]
Use of Irwin’s restricted mean as an index for comparing survival in different treatment groups– interpretation and power considerations
Karrison TG. Use of Irwin’s restricted mean as an index for comparing survival in different treatment groups– interpretation and power considerations. Controlled Clinical T rials 1997 Apr;18(2):151–167
1997
-
[20]
A Structural Approach to Selection Bias
Hernán MA, Hernández-Díaz S, Robins JM. A Structural Approach to Selection Bias. Epidemiology 2004 Sep;15(5):615. https://journals.lww.com/epidem/fulltext/2004/09000/a_structural_approach_to_selection_bias.20.aspx
2004
-
[21]
Causal estimands and confidence intervals associated with Wilcoxon-Mann-Whitney tests in randomized experiments
Fay MP , Brittain EH, Shih JH, Follmann DA, Gabriel EE. Causal estimands and confidence intervals associated with Wilcoxon-Mann-Whitney tests in randomized experiments. Statistics in Medicine 2018 Sep;37(20):2923–2937
2018
-
[22]
On Comparing Two T reatments
Hand DJ. On Comparing Two T reatments. The American Statistician 1992 Aug;46(3):190–192
1992
-
[23]
The win ratio: a new approach to the analysis of composite endpoints in clinical trials based on clinical priorities
Pocock SJ, Ariti CA, Collier TJ, Wang D. The win ratio: a new approach to the analysis of composite endpoints in clinical trials based on clinical priorities. European Heart Journal 2012 Jan;33(2):176–182. Ortholand et al. 21
2012
-
[24]
Hypothetical Estimands in Clinical T rials: A Unification of Causal Inference and Missing Data Methods
Olarte Parra C, Daniel RM, Bartlett JW. Hypothetical Estimands in Clinical T rials: A Unification of Causal Inference and Missing Data Methods. Statistics in Biopharmaceutical Research 2023;15(2):421–432.https://pmc.ncbi.nlm.nih. gov/articles/PMC10228513/
2023
-
[25]
Olarte Parra C, Daniel RM, Wright D, Bartlett JW. Estimating hypothetical estimands with causal inference and missing data estimators in a diabetes trial case study. Biometrics 2025 Mar;81(1):ujae167.https://doi.org/10.1093/biomtc/ ujae167
-
[26]
Identifiability and exchangeability for direct and indirect effects
Robins JM, Greenland S. Identifiability and exchangeability for direct and indirect effects. Epidemiology (Cambridge, Mass) 1992 Mar;3(2):143–155
1992
-
[27]
A causal framework for classical statistical estimands in failure time settings with competing events
Y oung JG, Stensrud MJ, T chetgen EJT, Hernán MA. A causal framework for classical statistical estimands in failure time settings with competing events. Statistics in medicine 2020 Jan;39(8):1199.https://pmc.ncbi.nlm.nih.gov/articles/ PMC7811594/
2020
-
[28]
Causal Inference for Statistics, Social, and Biomedical Sciences: An Introduction
Imbens GW, Rubin DB. Causal Inference for Statistics, Social, and Biomedical Sciences: An Introduction. 1 ed. Cambridge University Press; 2015.https://www.cambridge.org/core/product/identifier/9781139025751/type/book
-
[29]
PyMC: A Modern and Comprehensive Probabilistic Programming Framework in Python
Abril-Pla O, Andreani V, Carroll C, Dong L, Fonnesbeck CJ, Kochurov M, et al. PyMC: A Modern and Comprehensive Probabilistic Programming Framework in Python. PeerJ Computer Science 2023;9(e1516)
2023
-
[30]
Bayesian Survival Analysis
Austin Rochford CF Fernando Irarrazaval. Bayesian Survival Analysis. In: T eam P , editor. PyMC examples
-
[31]
The No-U-T urn Sampler: Adaptively Setting Path Lengths in Hamiltonian Monte Carlo
Hoffman MD, Gelman A. The No-U-T urn Sampler: Adaptively Setting Path Lengths in Hamiltonian Monte Carlo. Journal of Machine Learning Research 2014
2014
-
[32]
https:/ /grodri.github.io/glms/notes/
Rodríguez G, Lecture Notes on Generalized Linear Models; 2007. https:/ /grodri.github.io/glms/notes/
2007
-
[33]
<notebook title>
<notebook authors sa. <notebook title>. In: T eam P , editor. PyMC examples
-
[34]
Covariance Analysis of Censored Survival Data Using Log-Linear Analysis T echniques
Laird N, Olivier D. Covariance Analysis of Censored Survival Data Using Log-Linear Analysis T echniques. Journal of the American Statistical Association 1981;76(374):231–240.https://www.jstor.org/stable/2287816, publisher: [Ameri- can Statistical Association, T aylor & Francis, Ltd.]
-
[35]
The Analysis of Rates and of Survivorship Using Log-Linear Models
Holford TR. The Analysis of Rates and of Survivorship Using Log-Linear Models. Biometrics 1980;36(2):299–305. https://www.jstor.org/stable/2529982, publisher: [Wiley, International Biometric Society]
-
[36]
Sensitivity analyses for the principal ignorability assumption using multiple impu- tation
Wang C, Zhang Y, Mealli F, Bornkamp B. Sensitivity analyses for the principal ignorability assumption using multiple impu- tation. Pharmaceutical Statistics 2022;https://sci-hub.red/https://onlinelibrary.wiley.com/doi/epdf/10.1002/ pst.2260
2022
-
[37]
arXiv; 2025.http: //arxiv.org/abs/2501.16933, arXiv:2501.16933 [stat]
Even M, Josse J, Rethinking the Win Ratio: A Causal Framework for Hierarchical Outcome Analysis. arXiv; 2025.http: //arxiv.org/abs/2501.16933, arXiv:2501.16933 [stat]
-
[38]
arXiv; 2025.http://arxiv.org/abs/2503.05225, arXiv:2503.05225 [stat]
Orsini L, Lesaffre E, Yin G, Brard C, Dejardin D, T euff GL, Bayesian analysis of restricted mean survival time adjusted for covariates using pseudo-observations. arXiv; 2025.http://arxiv.org/abs/2503.05225, arXiv:2503.05225 [stat]
-
[39]
Using Simulation Studies to Evaluate Statistical Methods
Morris TP , White IR, Crowther MJ. Using Simulation Studies to Evaluate Statistical Methods. Statistics in Medicine 2019 May;38(11):2074–2102. 22 Ortholand et al
2019
-
[40]
A Phase II-III T rial of Olesoxime in Subjects with Amyotrophic Lateral Sclerosis
Lenglet T, Lacomblez L, Abitbol JL, Ludolph A, Mora JS, Robberecht W, et al. A Phase II-III T rial of Olesoxime in Subjects with Amyotrophic Lateral Sclerosis. European Journal of Neurology 2014 Mar;21(3):529–536
2014
-
[41]
scikit-survival: A Library for Time-to-Event Analysis Built on T op of scikit-learn
Pölsterl S. scikit-survival: A Library for Time-to-Event Analysis Built on T op of scikit-learn. Journal of Machine Learning Research 2020;21(212):1–6.http://jmlr.org/papers/v21/20-729.html
2020
-
[42]
Clinical significance in the change of decline in ALSFRS-R
Castrillo-Viguera C, Grasso DL, Simpson E, Shefner J, Et A. Clinical significance in the change of decline in ALSFRS-R. Amyotrophic Lateral Sclerosis 2010;https://sci-hub.box/10.3109/17482960903093710
-
[43]
T ransparent Parametrizations of Models for Potential Outcomes
Richardson TS, Evans RJ, Robins JM. T ransparent Parametrizations of Models for Potential Outcomes. In: Bernardo JM, Bayarri MJ, Berger JO, Dawid AP , Heckerman D, Smith AFM, et al., editors. Bayesian Statistics 9 Oxford University Press; 2011.p. 569–610.https://academic.oup.com/book/1879/chapter/141661815. Ortholand et al. 23 A|SIMULATION MAIN STUDY A.1|...
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.