Format

Send to

Choose Destination
Epidemiology. 2016 Jul;27(4):525-30. doi: 10.1097/EDE.0000000000000493.

Collider Bias Is Only a Partial Explanation for the Obesity Paradox.

Author information

1
From the aHealth eResearch Centre, Farr Institute, and bInstitute of Cancer Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom.

Abstract

BACKGROUND:

"Obesity paradox" refers to an association between obesity and reduced mortality (contrary to an expected increased mortality). A common explanation is collider stratification bias: unmeasured confounding induced by selection bias. Here, we test this supposition through a realistic generative model.

METHODS:

We quantify the collider stratification bias in a selected population using counterfactual causal analysis. We illustrate the bias for a range of scenarios, describing associations between exposure (obesity), outcome (mortality), mediator (in this example, diabetes) and an unmeasured confounder.

RESULTS:

Collider stratification leads to biased estimation of the causal effect of exposure on outcome. However, the bias is small relative to the causal relationships between the variables.

CONCLUSIONS:

Collider bias can be a partial explanation of the obesity paradox, but unlikely to be the main explanation for a reverse direction of an association to a true causal relationship. Alternative explanations of the obesity paradox should be explored. See Video Abstract at http://links.lww.com/EDE/B51.

PMID:
27075676
PMCID:
PMC4890843
DOI:
10.1097/EDE.0000000000000493
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Wolters Kluwer Icon for PubMed Central
Loading ...
Support Center