Previous research has shown disparities between sexes exist related to risk and outcomes of AAA. While females are generally protected from the development of AAAs, the ones that do develop behave more aggressively with higher growth and rupture rates, and are more likely to result in death24,25. However, to our knowledge, there has not been a multiyear comprehensive assessment of the disparities between females and males with regards to outcomes following hospitalization for rAAA. Using 13 years of data from the largest publicly available database of US inpatient stays, we found significant differences between females and males presenting to the hospital with a primary diagnosis of rAAA.

There were significant decreases in the rate of hospitalizations for rAAA among both females and males from 2002 through 2014. However, the hospital charges increased significantly for both sexes during the same time period. These rising charges were not due to increasing time spent in the hospital – the mean length of stay for males with rAAA was 11.3 days in 2002 and 9.5 days in 2014, compared with 9.4 days in 2002 and 6.6 days in 2014 for females (data not shown). Increasing hospital charges are most likely due to a variety of factors, including utilization of new technology and increasing drug prices.

We also investigated potential interaction effects between patient sex and time for dependent variables of adjusted mean charges and hospitalization rate – these analyses were conducted to investigate if the delta between sexes for each dependent variable changed significantly over time. The interaction between sex and time for mean hospital charges resulted in a P value of 0.100, though the interaction effect for hospitalization rate was <0.001. This suggests that while the rate of rAAA hospitalizations decreased over time for both sexes, the delta between the rate for males and that for females decreased significantly over time.

There were also significant decreases over time for both sexes in the proportion of patients dying in the hospital, though in each year females had a higher in-hospital mortality rate than males. After adjusting for potential confounders, we found that overall females had 35% higher odds of mortality than males despite having similar van Walraven Elixhauser comorbidity scores with males and similar perioperative complications. This confirms previous research showing that females with AAA tend to have disproportionately worse outcomes than men14,25. The United States Preventive Services Task Force (USPSTF) has historically not recommended screening for AAA in females regardless of risk factors, though, as of the writing of the manuscript, the USPSTF is considering a revised draft plan for AAA screening that would include asymptomatic adults in both sexes26. It is possible that if this plan is implemented, we may see a reduction in the mortality disparity between males and females with rAAA. Due to the fact that AAAs are often asymptomatic until they rupture, it is not unreasonable to assume that the prevalence is currently underdiagnosed. However, AAA screening can also potentially lead to the opposite problem of overdiagnosis. Most screen-detected AAAs are small (70% are <40 mm in diameter), which, while having low risk of rupture, can lead to other harms for some patients, such as psychological burden and unnecessary surgery27.

We performed separate analyses on sex disparities among those receiving EVAR and OAR. The proportion of rAAA patients who received EVAR increased substantially for both males and females, while the proportion receiving OAR decreased. We also examined the interaction between sex and time for both surgeries to investigate the delta between males and females. The interaction for EVAR yielded a P value of 0.062, while for OAR the interaction P value was 0.118. These results suggest that while clearly the gaps between sexes in terms of the proportions receiving EVAR or receiving OAR have widened and narrowed, respectively, the results were not quite statistically significant.

Females who received EVAR were significantly more likely to die than males, even after adjusting for potential confounders. Interestingly, this disparity in mortality occurred despite no significant differences in any of the perioperative complications studied. Females who received OAR were also significantly more likely to die than males, though the result just met our significance threshold of 0.05. However, among these patients, females were shown to have a significant protective effect in the odds of perioperative venous thromboembolism and bowel obstruction, and no significant differences were shown for the other perioperative complications.

Disparities in mortality between sexes persisted across the study period. We separately calculated adjusted odds of in-hospital death for females vs males in each year, and found that consistently females had higher risk than males. Despite decreasing mortality rates for both sexes, females have remained at higher risk of death compared with males.

There are many potential reasons for these outcome disparities, including differences in diagnosis and treatment rates or inherent anatomic dissimilarities. It is also possible that the lack of recommended one-time screening for AAA in females could be partially responsible. However, it is clear that greater focus is needed on improving rAAA outcomes among females, and additional research is necessary to determine potential underlying pathophysiological explanations for outcome disparities between sexes.

While this study provides valuable information on disparities in outcomes for rAAA between sexes, there are some important limitations that warrant further examination. The NIS database is an administrative data set originally generated for billing purposes and is vulnerable to coding errors and incomplete data. We analyzed 13 years of data, consisting of over 75,000 hospitalizations for rAAA, which should diminish the effect of any potential coding errors. Similarly, due to the nature of administrative data we were unable to discern information on the pathophysiology of each patient’s AAA, including diameter of the ruptured vessel, vessel tortuosity, and site of rupture (intraperitoneal cavity or retroperitoneal cavity). Each of these variables may influence perioperative complications or in-hospital mortality and may have an effect on whether a patient is an appropriate candidate for EVAR or OAR. Finally, the NIS is restricted to in-hospital data and does not provide information on long-term outcomes.

Despite these potential limitations, this study has some notable strengths. Using 13 years of data from the largest publicly-available all-payer inpatient database in the United States, we conducted the first comprehensive study to focus on outcome disparities in hospitalizations for rAAA between females and males. Future research could focus on conducting similar analyses in the emergency department setting, which in conjunction with the results of this study would provide a complete picture of the clinical and economic characteristics of rAAA patients in the ED and hospital.