ArticleEpidemiology (Cambridge, Mass.)2021
To Adjust or Not to Adjust? When a "Confounder" Is Only Measured After Exposure.
Article in Epidemiology (Cambridge, Mass.), 2021. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 38 papers, 2 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
38 citing papers in PubMed, 2 syntheses or guidelines pooled it.
- Sodium Glucose Co-Transporter 2 Inhibitors and Ventricular Arrhythmias in Patients with Type 2 Diabetes: A Systematic Review of Observational Studies.Drug safety · 2026Pooled it
- The Same but Different?: A Systematic Review of the Impact of Selection and Collider Bias on Internal Validity.Epidemiology (Cambridge, Mass.) · 2025Pooled it
- Second Primary Malignancy Risk in Patients with Multiple Myeloma Receiving CAR T-cell Therapy or Other Systemic Anticancer Treatments: A Real-World Comparative Study.Clinical cancer research : an official journal of the American Association for Cancer Research · 2026Article
- Not always towards the null: reconsidering the direction of overadjustment bias.International journal of epidemiology · 2026Article
- Article
- A comparison of the safety of oral labetalol versus nifedipine to manage hypertension in pregnancy in Australia: a target trial emulation.EClinicalMedicine · 2026Article
- Mid-Term Oncological Outcomes of Vaginal Natural Orifice Transluminal Endoscopic Surgery Compared with Total Laparoscopic Hysterectomy for Early-Stage Endometrial Cancer: A Single-Center Retrospective Study.Journal of clinical medicine · 2026Article
- Genetic Variants Associated with Life Expectancy in Patients with Chagas Disease.Medical sciences (Basel, Switzerland) · 2026Article
- Obesity and self-rated health in middle-aged Danes.International journal of obesity (2005) · 2026Article
- Glucose-lowering effects of physical activity in type 1 diabetes: A causal modelling and matched-pair analysis approach.Diabetic medicine : a journal of the British Diabetic Association · 2025Article
- Cytomegalovirus Viral Load Continues to Predict Poor Outcomes in Adults and Children Despite Improved Hematopoietic Cell Transplantation Success.Open forum infectious diseases · 2025Article
- Evaluation of Methods Adjusting for Unmeasured Confounding Using Large Healthcare Databases: An Empirical Study Concerning Drugs Inducing Prematurity.Clinical and translational science · 2025Article
- Associations of hepatitis C virus (HCV) antibody positivity with opioid, stimulant, and polysubstance injection among people who inject drugs (PWID) in rural U.S. communities.The International journal on drug policy · 2025Article
- Are associations of adulthood overweight and obesity with all-cause mortality, cardiovascular disease, and obesity-related cancer modified by comparative body weight at age 10 years in the UK Biobank study?International journal of obesity (2005) · 2025Article
- Elevated risk of infection in individuals with hyperinsulinaemic type 2 diabetes: a Danish 12 year cohort study.Diabetologia · 2025Article
- A causal machine-learning framework for studying policy impact on air pollution: a case study in COVID-19 lockdowns.American journal of epidemiology · 2025Article
- Differences in hepatitis C virus (HCV) testing and treatment by opioid, stimulant, and polysubstance use among people who use drugs in rural U.S. communities.Harm reduction journal · 2024Article
- Determining individual suitability for neoadjuvant systemic therapy in breast cancer patients through deep learning.Clinical & translational oncology : official publication of the Federation of Spanish Oncology Societies and of the National Cancer Institute of Mexico · 2024Article
- LifeCourse Socioeconomic Position and Ideal Cardiovascular Health in Hispanic/Latino Adults of the Hispanic Community Health Study/Study of Latinos.Journal of the American Heart Association · 2024Article
- GATA6 identifies an immune-enriched phenotype linked to favorable outcomes in patients with pancreatic cancer undergoing upfront surgery.Cell reports. Medicine · 2024Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
3 authors.
Funding
Abstract
Advice regarding the analysis of observational studies of exposure effects usually is against adjustment for factors that occur after the exposure, as they may be caused by the exposure (or mediate the effect of exposure on outcome), so potentially leading to collider stratification bias. However, such factors could also be caused by unmeasured confounding factors, in which case adjusting for them will also remove some of the bias due to confounding. We derive expressions for collider stratification bias when conditioning and confounding bias when not conditioning on the mediator, in the presence of unmeasured confounding (assuming that all associations are linear and there are no interactions). Using simulations, we show that generally neither the conditioned nor the unconditioned estimate is unbiased, and the trade-off between them depends on the magnitude of the effect of the exposure that is mediated relative to the effect of the unmeasured confounders and their relations with the mediator. We illustrate the use of the bias expressions via three examples: neuroticism and mortality (adjusting for the mediator appears the least biased option), glycated hemoglobin levels and systolic blood pressure (adjusting gives smaller bias), and literacy in primary school pupils (not adjusting gives smaller bias). Our formulae and simulations can inform quantitative bias analysis as well as analysis strategies for observational studies in which there is a potential for unmeasured confounding.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.