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Socioeconomic status and surgical mortality in the elderly
Nancy J O Birkmeyer1, Niya Gu, Onur Baser
1Department of Surgery, Michigan Surgical Collaborative for Outcomes Research and Evaluation, University of Michigan, Ann Arbor, Michigan, USA. nbirkmey@umich.edu
Background:
Although racial disparities in the quality of surgical care are well described, the impact of socioeconomic status on operative mortality is relatively unexplored.
Methods:
We used Medicare data to identify all patients undergoing 1 of 6 common, high risk surgical procedures between 1999 and 2003. We constructed a summary measure of socioeconomic status for each US ZIP code using data from the 2000 US Census linked to the patient's ZIP code of residence. We assessed the effects of socioeconomic status on operative mortality rates while controlling for other patient characteristics and then examined the extent to which disparities in operative mortality could be attributed to differences in hospital factors.
Results:
Socioeconomic status was a significant predictor of operative mortality for all 6 procedures in crude analyses and in those adjusted for patient characteristics. Comparing the lowest quintile of socioeconomic status to the highest, the adjusted odds ratios (OR) and 95% confidence intervals (CI) ranged from OR = 1.17; 95% CI: 1.10-1.25 for colectomy to OR = 1.39; 95% CI: 1.18-1.65 for gastrectomy. After further adjustment for hospital factors, the odds ratio associated with socioeconomic status for coronary artery bypass (OR = 1.14; 95% CI: 1.09-1.19), aortic valve replacement (OR = 1.13; 95% CI: 1.04-1.23), and mitral valve replacement (OR = 1.11; 95% CI: 1.00-1.23) were diminished, and those for lung resection (OR = 0.93; 95% CI: 0.81-1.07), colectomy (OR = 1.04; 95% CI: 0.98-1.12), and gastrectomy (OR = 1.11; 95% CI: 0.90-1.38) were reduced and also were no longer statistically significant. Within hospitals, there were only small differences in adjusted operative mortality by patient socioeconomic status.
Conclusions:
Patients with lower socioeconomic status have higher rates of adjusted operative mortality than patients with higher socioeconomic status across a wide range of surgical procedures. These disparities in surgical outcomes are largely attributable to differences between the hospitals where patients of higher and lower socioeconomic status tend to receive surgical treatment.