Three-Toed Sloth

"Likelihood-Based Methods of Mediation Analysis in the Context of Health Disparities" (Next Week at the Statistics Seminar)

Attention conservation notice: Only of interest if you (1) care about evidence on how inequality matters for health, and (2) will be in Pittsbrugh on Tuesday.

Therri Usher, "Likelihood-Based Methods of Mediation Analysis in the Context of Health Disparities"

Abstract: African-Americans experience higher incidences of death and disability compared to non-Hispanic whites. Much of the existing research has focused on identifying the existence of health disparities, as methodological issues have hampered the development of health disparities research. In order to create solutions to eliminate health disparities, research must understand the mechanisms powering their existence.

Existing causal inference tools are not suitable for studying racial health disparities, as race cannot be manipulated or changed. For the same reason, mediators stand to be useful in creating avenues to intervene on existing health disparities. Structural equation modeling (SEM) may be a more promising tool for quantifying the causal framework of health disparities.

One of the most widely-used tests for assessing mediation is the Sobel test (Sobel, 1982; MacKinnon et al, 2007). However, it has disadvantages, including lower power at smaller sample sizes. Therefore, this work focuses on three varying methods for assessing mediation and compares their performance to the Sobel test.

The first method is an adjustment of the Sobel test that utilizes variance estimation using random covariates. The second method utilizes the joint distribution of the mediator and the outcome to determine profile likelihoods for the estimands of interest in order to derive distributions for their estimates. Finally, the third method utilizes Bayesian modeling techniques to fit the structural equation models and estimating the probability of mediation through quantile estimation. Simulations provided evidence that all three methods demonstrated comparable estimated statistical power compared to the Sobel test, often showcasing superior power at smaller sample sizes while providing more tools of inference into the presence of mediation.

The methods were applied to assess whether diet mediates the relationship between race and blood pressure in non-Hispanic black and white subjects in the National Health and Nutrition Examination Survey (NHANES) from 1999-2004.

Time and place: 4:30--5:30 pm on Tuesday, 23 February 2016, in Baker Hall A51

As always, the talk is free and open to the public.

Enigmas of Chance; Constant Conjunction Necessary Connexion