PurposeFrailty has shown promise in predicting postoperative morbidity and mortality following hernia surgery. This study aims to evaluate the predictive capacity of the 11-item modified frailty index (mFI) in estimating postoperative outcomes following elective hernia surgery using the National Inpatient Sample (NIS) database.MethodsA retrospective analysis of the NIS from 2015 to 2019 was performed including adult patients who underwent elective hernia repair. The mFI was used to stratify patients as either frail (mFI ≥ 0.27) or robust (mFI < 0.27). The primary outcomes were in-hospital postoperative morbidity and mortality. The secondary outcomes were system-specific morbidity, length of stay (LOS), total in-hospital healthcare cost, and discharge disposition. Univariable and multivariable regressions were utilized.ResultsIn total, 14,125 robust patients and 1704 frail patients were included. Frailty was associated with an increased age (mean age 66.4 years vs. 52.6 years, p < 0.001) and prevalence of ventral hernias (51.9% vs. 44.4%, p < 0.001). Adjusted analyses demonstrated that frail patients had increased in-hospital mortality (adjusted odds ratio (aOR) 3.89, 95% CI 1.50, 10.11, p = 0.005), postoperative overall morbidity (aOR 1.98, 95% CI 1.72, 2.29, p < 0.001), postoperative LOS (adjusted mean difference (aMD) 0.78 days, 95% CI 0.51, 1.06, p < 0.001), total in-hospital healthcare costs (aMD $7562 95% CI 3292, 11,832, p = 0.001), and were less likely to be discharged home (aOR 0.61, 95% CI 0.53, 0.69, p < 0.001).ConclusionThe mFI may be a reliable predictor of postoperative morbidity and mortality in elective hernia surgery. Utilizing this tool can aid in patient education and identifying high-risk patients who may benefit from tailored prehabilitation.