Trends in In-hospital Coronary Artery Bypass Surgery Mortality by Gender and Race/Ethnicity --1998-2015: Why Do the Differences Remain?

Abstract Background and aims Between 1998 and 2015, the national coronary artery bypass graft surgery (CABG) in-hospital mortality rate fell nearly 45% to just 2.2% of CABG in-patients. By almost any standards, this large decline in the nation's in-hospital mortality for CABG inpatients has been extraordinary. Yet, over this time period, no studies have detailed these notable trends in in-hospital CABG mortality with an emphasis on the differences by gender and racial/ethnicity. The in-hospital CABG treatment period is the approximately 9 day inpatient length-of-stay the patient is completely under the care of hospital and its staff. Our research seeks to fill this research gap with analyses of 18 years of national data of over 5 million CABG inpatient discharges distinguishing gender by six categories of race/ethnicity (Asian, black, Hispanic, white, other known races/ethnicities, and unknown race/ethnicities) to evaluate three broad questions related to in-hospital CABG mortality: 1) What have been the 18-year national trends in CABG surgeries, length-of-stay, mortality, and type of discharge by gender and race/ethnicity? 2) Over time, what have been the in-hospital mortality trends by gender and race-ethnicity? 3) Using multivariate techniques to control for patient characteristics, risk factors and socioeconomic characteristics of the hospital setting and environment, what is the extent of the variations in in-hospital mortality among the 12 groupings of gender and race-ethnicity? Data and methods Data are from the Nationwide Inpatient Sample (NIS) data from the Healthcare Utilization Project (HCUP–NIS) collected yearly. These data represent 858 hospitals, a 20% national sample representing 5,032,985 CABG patient discharges from hospitals over an 18-year period -- 1998 to 2015. Descriptive and logistic regression analyses are used to evaluate the outcomes. Results The national decline in in-hospital CABG mortality trends over the 18-year period has been dramatic. These declines have substantially impacted all 12 racial/ethnic and gender groupings analyzed during this timeframe. However, over the 18-year period, both univariate and logistic regression results reveal the disadvantages females and black males have in in-hospital CABG mortality rates when compared to the comparison group, white male CABG inpatients. Female CABG inpatients consistently, regardless of their race/ethnicity, have significantly higher in-hospital mortality rates than their corresponding male counterparts even after controlling for patient characteristics and socio-economic status. For males, however, the likelihood of dying in the hospital from a CABG procedure showed wide variation across the four racial/ethnic categories. Compared with white male patients undergoing CABG surgery in the nation's hospitals, after controlling for confounding factors, Hispanic and Asian-American had significantly lower in-hospital CABG mortality rates −9.7% and −17.9% respectively. In contrast, black male CABG patients had a 35.1% higher in-hospital CABG mortality rate than white males. Conclusions While considerable progress has been made reducing overall in-hospital CABG mortality over the past 18-years across all gender and racial/ethnic inpatients, significant gaps persist between black males and other racial/ethnic groups.