Immortal Time Bias in Epidemiology

Platt, Robert W.; Hutcheon, Jennifer A.; Suissa, Samy

doi:10.1007/s40471-019-0180-5

Cited by 31 publications

(44 citation statements)

References 18 publications

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“…When the outcome is a function of time at risk, and time-varying exposures are assessed as though they occurred at the start of follow up (or in this case, at conception), immortal time bias can result. 49 To address this, we analysed time to birth as a survival outcome, first conducting descriptive analyses using Kaplan-Meier survival plots and then estimating time-varying Cox proportional hazard models stratified by census tract. 50 This approach allows the person-time in exposed and unexposed states to be accurately represented in the estimation and permits each census tract to have its own baseline hazard, analogous to including a fixed effect on each census tract.…”

Section: Discussionmentioning

confidence: 99%

Occurrence of fatal police violence during pregnancy and hazard of preterm birth in California

Goin

Gómez

Farkas

et al. 2021

Paediatric Perinatal Epid

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Background: Exposure to fatal police violence may play a role in population-level inequities in risk for preterm delivery.Objective: To evaluate whether exposure to fatal police violence during pregnancy affects the hazard of preterm delivery and whether associations differ by race/ethnicity and fetal sex. Methods:We leveraged temporal variation in incidents of fatal police violence within census tracts to assess whether occurrence of fatal police violence in a person's tract during pregnancy was associated with increased hazard of extremely (20-27 weeks), early (28-31 weeks), moderate (32-33 weeks), and late (32-36 weeks) preterm delivery in California from 2007 to 2015. We used both death records and the Fatal Encounters database to identify incidents of fatal police violence. We estimated hazard ratios (HR) using time-varying Cox proportional hazard models stratified by census tract, controlling for age, race/ethnicity, educational attainment, health insurance type, parity, and the year and season of conception. We further stratified by race/ ethnicity and infant sex to evaluate whether there were differential effects by these characteristics.

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Section: Discussionmentioning

confidence: 99%

Occurrence of fatal police violence during pregnancy and hazard of preterm birth in California

Goin

Gómez

Farkas

et al. 2021

Paediatric Perinatal Epid

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“…To prevent immortaltime bias-namely, considering hazard periods during which the study outcome cannot occur, time at risk was defined as the number of days when the persons were not hospitalised. 25 Hospitalisations separated by 1 day or less were concatenated into a single episode in order to avoid counting transfers from one hospital unit to another as separate admissions. Incidence rates and their 95% CIs were calculated per 100 personyears or per 100 person-weeks, as appropriate.…”

Section: Outcomementioning

confidence: 99%

Unplanned hospitalisations in older people: illness trajectories in the last year of life

Szilcz

Wastesson

Johnell

et al. 2021

BMJ Support Palliat Care

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ObjectiveUnplanned hospitalisations can be burdensome for older people who approach the end of life. Hospitalisations disrupt the continuity of care and often run against patients’ preference for comfort and palliative goals of care. This study aimed to describe the patterns of unplanned hospitalisations across illness trajectories in the last year of life.MethodsLongitudinal, retrospective cohort study of decedents, including all older adults (≥65 years) who died in Sweden in 2015. We used nationwide data from the National Cause of Death Register linked at the individual level with several other administrative and healthcare registers. Illness trajectories were defined based on multiple-cause-of-death data to approximate functional decline near the end of life. Incidence rate ratios (IRR) for unplanned hospitalisations were modelled with zero-inflated Poisson regressions.ResultsIn a total of 77 315 older decedents (53% women, median age 85.2 years), the overall incidence rate of unplanned hospitalisations during the last year of life was 175 per 100 patient-years. The adjusted IRR for unplanned hospitalisation was 1.20 (95%CI 1.18 to 1.21) times higher than average among decedents who followed a trajectory of cancer. Conversely, decedents who followed the trajectory of prolonged dwindling had a lower-than-average risk of unplanned hospitalisation (IRR 0.66, 95% CI 0.65 to 0.68). However, these differences between illness trajectories only became evident during the last 3 months of life.ConclusionOur study highlights that, during the last 3 months of life, unplanned hospitalisations are increasingly frequent. Policies aiming to reduce burdensome care transitions should consider the underlying illness trajectories.

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“…We found a reduced survival time after testing in MAP ELISA test positive dairy cows. In our model the time from ELISA testing to culling was analyzed instead of the age at culling to avoid immortal time bias (37). Controlling for immortal time bias was necessary, because cattle had to remain in the herd for a sufficiently long time period to be tested (they could not be culled earlier, e.g., as heifers prior to testing).…”

Section: Cullingmentioning

confidence: 99%

The Impact of Paratuberculosis on Milk Production, Fertility, and Culling in Large Commercial Hungarian Dairy Herds

et al. 2020

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Paratuberculosis (PTBC) is a chronic disease caused by Mycobacterium avium subsp. paratuberculosis (MAP), which is common in dairy herds worldwide, although the scale of its impact on herd productivity is unclear. The aim of our study was to determine the differences between MAP ELISA positive vs. negative cows in terms of milk production and quality, reproductive parameters, and culling. The data of five large dairy herds that participated in the voluntary PTBC testing program in Hungary were analyzed. Cows were tested by ELISA (IDEXX Paratuberculosis Screening Ab Test, IDEXX Laboratories, Inc., Westbrook, ME, USA) using milk samples collected during official performance testing. The outcome of the initial screening test involving all milking cows in the herds was used for the classification of the cows. The 305-day milk production, reproduction and culling data of 4,341 dairy cows, and their monthly performance testing results (n = 87,818) were analyzed. Multivariate linear and logistic models, and right censored tobit model were used for the statistical analysis. Test-day and 305-day milk production of ELISA positive cows decreased by 4.6 kg [95% CI: 3.5-5.6 kg, P < 0.0001 (−13.2%)] and 1,030 kg [95% CI: 708-1,352 kg, P < 0.0001 (−9.4%)], compared to their ELISA negative herdmates, respectively. Milk ELISA positive cows had 35.8% higher [95% CI: 17.9-56.4%, P < 0.0001] somatic cell count, on average. Test positive cows conceived 23.2 days later [95% CI: 9.2-37.3 days, P = 0.0012 (+16.5%)] and their calving interval was 33.8 days longer [95% CI: 13.2-54.4 days, P = 0.0013, (+9.7%)], compared to the negative cows, on average. Milk ELISA positive cows were less likely to conceive to first insemination (odds ratio: 0.49, 95% CI: 0.31-0.75, P = 0.0013), and required 0.42 more inseminations to conceive [95% CI: 0.07-0.77, P = 0.0192 (+13.7%)], on average. Milk ELISA positive cows were culled 160.5 days earlier after testing compared to their ELISA negative herdmates (95% CI: 117.5-203.5 days, P < 0.0001). Our results suggest that MAP ELISA positive cows experience decreased milk production, milk quality, fertility, and longevity, which supports the need to control the prevalence of PTBC in dairy herds.

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Immortal Time Bias in Epidemiology

Cited by 31 publications

References 18 publications

Occurrence of fatal police violence during pregnancy and hazard of preterm birth in California

Occurrence of fatal police violence during pregnancy and hazard of preterm birth in California

Unplanned hospitalisations in older people: illness trajectories in the last year of life

The Impact of Paratuberculosis on Milk Production, Fertility, and Culling in Large Commercial Hungarian Dairy Herds

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