Abstract P198: Racial Disparities in Cardiovascular Outcomes in REGARDS Persist After Using Inverse Probability Weighting to Account for Missing Data

Abstract

Introduction: When data are missing, analysts often choose to perform ‘complete case’ analysis, restricting statistical analysis to those participants with all necessary fields completed. However, this analysis is subject to selection bias if those participants excluded are somehow inherently different from those included. One approach to address the potential selection bias is inverse probability weighting, where participants with complete data are weighted to reflect the original population. We compare estimated racial disparities in hypertension and left ventricular hypertrophy using complete cases to those estimates from inverse probability weighted analysis. Methods: The REasons for Geographic and Racial Differences in Stroke (REGARDS) study enrolled 30,183 participants aged 45+ between 2003 and 2007 to study racial and geographic differences in stroke and cardiovascular health. When the second in-home visits were conducted, 18% (5542) of participants had died and 23% (7071) of participants had withdrawn. For the baseline population, the probabilities of being a complete case are estimated through logistic regression models using baseline characteristics. These predicted probabilities are inverted to create the weights used in statistical analysis, such that the complete participants are weighted to represent the enrolled population. Through logistic regression, we estimate the association between race and hypertension and left ventricular hypertrophy at the second in-home visit for complete data and compare these results to the results from inverse probability weighted analysis. All models are adjusted for sex, age and region. Results: The logistic models for dropout and death have low and moderate predictive abilities (c-statistics 0.602 and 0.811, respectively). For incident hypertension, the estimated odds ratio comparing blacks to whites differs little between the complete case (1.87 (1.66, 2.10)) and the weighted (1.83 (1.61, 2.09)) analysis. For left ventricular hypertrophy, the estimated odds ratio comparing blacks to whites changes little from the complete case analysis (1.54 (1.32, 1.79)) to the weighted analysis (1.45 (1.21, 1.74)). Discussion: Estimated racial inequalities in the odds of incident hypertension and left ventricular hypertrophy were similar in the complete case and inverse probability weighting analyses, indicating little evidence of selection bias in the estimation of racial inequalities for these outcomes.