BackgroundFrailty has been associated with increased postoperative mortality and morbidity; however, the use of the modified frailty index (mFI-11) to assess patients undergoing surgery for diverticular disease has not been widely assessed. This paper aims to examine frailty, evaluated by mFI-11, to assess postoperative morbidity and mortality among patients undergoing operative intervention for colonic diverticular disease.MethodsWe used data from the Healthcare Cost and Utilization Project National Inpatient Sample (October 1, 2015–December 31, 2019). ICD-10-CM codes were utilized to identify a cohort of adult patients with a primary admission diagnosis of diverticulitis. mFI-11 items were adapted to correspond with ICD-10-CM codes. Patients were stratified into robust (mFI < 0.27) and frail (mFI ≥ 0.27) groups. Primary outcomes were in-hospital postoperative morbidity and mortality. Secondary outcomes included system-specific postoperative complications, length of stay (LOS), total admission cost, and discharge disposition. Multivariable regression models were fit.ResultsOf the 26,826 patients, there were 24,194 patients with mFI-11 < 0.27 (i.e., robust) and 2,632 patients with mFI-11 ≥ 0.27 (i.e., frail). Adjusted analysis showed significant increases in postoperative mortality (aOR 2.16, 95% CI 1.38–3.38, p = 0.001) and overall postoperative morbidity (aOR 1.84, 95% CI 1.65–2.06, p < 0.001). LOS was higher in the frail group (MD 1.78 days, 95% CI 1.46–2.11, p < 0.001) as well as total cost (MD $25,495.19, 95% CI $19,851.63-$31,138.75, p < 0.001).ConclusionIn the elective setting, a high mFI-11 (i.e., presence of the variables comprising the index) could alert clinicians to the possibility of implementing preoperative optimization strategies. In the emergent setting, a high mFI-11 may help guide prognostication for these vulnerable patients.