Selection of confounding variables should not be based on observed associations with exposure.
TLDR
Clinical data on the effects of inhaled long-acting beta-agonist use on the risk of mortality among patients with obstructive pulmonary disease was used to illustrate the impact of selection of confounding variables for adjustment based on baseline comparisons.Abstract:
In observational studies, selection of confounding variables for adjustment is often based on observed baseline incomparability. The aim of this study was to evaluate this selection strategy. We used clinical data on the effects of inhaled long-acting beta-agonist (LABA) use on the risk of mortality among patients with obstructive pulmonary disease to illustrate the impact of selection of confounding variables for adjustment based on baseline comparisons. Among 2,394 asthma and COPD patients included in the analyses, the LABA ever-users were considerably older than never-users, but cardiovascular co-morbidity was equally prevalent (19.9% vs. 19.9%). Adjustment for cardiovascular co-morbidity status did not affect the crude risk ratio (RR) for mortality: crude RR 1.19 (95% CI 0.93–1.51) versus RR 1.19 (95% CI 0.94–1.50) after adjustment for cardiovascular co-morbidity. However, after adjustment for age (RR 0.95, 95% CI 0.76–1.19), additional adjustment for cardiovascular co-morbidity status did affect the association between LABA use and mortality (RR 1.01, 95% CI 0.80–1.26). Confounding variables should not be discarded based on balanced distributions among exposure groups, because residual confounding due to the omission of confounding variables from the adjustment model can be relevant.read more
Citations
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Reduction of Red and Processed Meat Intake and Cancer Mortality and Incidence: A Systematic Review and Meta-analysis of Cohort Studies.
Mi Ah Han,Dena Zeraatkar,Gordon H Guyatt,Robin W.M. Vernooij,Regina El Dib,Ying Zhang,Abdullah Algarni,Gareth Leung,Dawid Storman,Claudia Valli,Montserrat Rabassa,Nadia Rehman,Michael K. Parvizian,Max Zworth,Jessica J Bartoszko,Luciane Cruz Lopes,Daegan Sit,Malgorzata M Bala,Pablo Alonso-Coello,Bradley C. Johnston +19 more
TL;DR: This current review focuses on observational studies addressing cancer outcomes and summarized results from cohort studies by conducting doseresponse meta-analyses and used the GRADE (Grading of Recommendations Assessment, Development and Evaluation) methodology to rate the certainty of evidence supporting the absolute effects of meat consumption on cancer incidence and mortality.
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Visual impairment and the incidence of falls and fractures among older people: longitudinal findings from the Blue Mountains Eye Study.
TL;DR: In this older cohort, recent development of visual impairment was associated with increased likelihood of subsequent falls and fractures in the next 5 years, independent of other confounding variables.
Journal ArticleDOI
Low serum magnesium levels are associated with increased risk of fractures: a long-term prospective cohort study
TL;DR: In middle-aged Caucasian men, low serum magnesium is strongly and independently associated with an increased risk of fractures and further research is needed to assess the potential relevance of serum magnesium in the prevention of fractures.
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Impact of postoperative complications on outcomes after oesophagectomy for cancer
TL;DR: The aim of this study was to identify the most clinically relevant complications after oesophagectomy for cancer in a nationwide cohort study.
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Cardiac (82)Rb PET/CT for fast and non-invasive assessment of microvascular function and structure in asymptomatic patients with type 2 diabetes.
Bernt Johan von Scholten,Philip Hasbak,Thomas Emil Christensen,Adam Ali Ghotbi,Andreas Kjaer,Peter Rossing,Peter Rossing,Peter Rossing,Tine W. Hansen +8 more
TL;DR: Type 2 diabetic patients who were free of overt cardiovascular disease had a high prevalence of coronary microvascular dysfunction, especially with concomitant albuminuria, suggesting a common microv vascular impairment occurring in multiple microv artery beds.
References
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Simulation Study of Confounder-Selection Strategies
TL;DR: The authors compared the performance of several such strategies for fitting multiplicative Poisson regression models to cohort data, finding that the change-in-estimate and equivalence-test-of-the-difference strategies performed best when the cut-point for deciding whether crude and adjusted estimates differed by an important amount was set to a low value.
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Estimating the Relative Risk in Cohort Studies and Clinical Trials of Common Outcomes
TL;DR: The purpose of this paper is to discuss the incorrect application of a proposed method to estimate an adjusted relative risk from an adjusted odds ratio, which has quickly gained popularity in medical and public health research, and to describe alternative statistical methods for estimating anadjusted relative risk when the outcome is common.
Book
Epidemiology: An introduction
TL;DR: This chapter discusses epidemiologic thinking in clinical settings, the role of statistics, and methods for controlling Confounding by Stratifying Data.
Journal ArticleDOI
Variable Selection for Propensity Score Models
M. Alan Brookhart,Sebastian Schneeweiss,Kenneth J. Rothman,Kenneth J. Rothman,Robert J. Glynn,Jerry Avorn,Til Stürmer +6 more
TL;DR: The authors present the results of two simulation studies designed to help epidemiologists gain insight into the variable selection problem in a PS analysis, which suggest that standard model-building tools designed to create good predictive models of the exposure will not always lead to optimal PS models, particularly in small studies.
Journal ArticleDOI
Quantifying biases in causal models: classical confounding vs collider-stratification bias.
TL;DR: The results suggest that bias from stratifying on variables affected by exposure and disease may often be comparable in size with bias from classical confounding, whereas other biases from collider stratification may tend to be much smaller.