Association of the Modified Frailty Index With 30-Day Surgical Readmission

Abstract

Importance: Frail patients are known to have poor perioperative outcomes. There is a paucity of literature investigating how the Modified Frailty Index (mFI), a validated measure of frailty, is associated with unplanned readmission among military veterans following surgery.

Objective: To understand the association between frailty and 30-day postoperative unplanned readmission.

Design, setting, and participants: A retrospective cohort study was conducted among adult patients who underwent surgery and were discharged alive from Veterans Affairs hospitals for orthopedic, general, and vascular conditions between October 1, 2007, and September 30, 2014, with a postoperative length of stay between 2 and 30 days.

Exposure: Frailty, as calculated by the 11 variables on the mFI.

Main outcomes and measures: The primary outcome of interest is 30-day unplanned readmission. Secondary outcomes included any 30-day predischarge or postdischarge complication, 30-day postdischarge mortality, and 30-day emergency department visit.

Results: The study sample included 236 957 surgical procedures (among 223 877 men and 13 080 women; mean [SD] age, 64.0 [11.3] years) from high-volume surgical specialties: 101 348 procedures (42.8%) in orthopedic surgery, 92 808 procedures (39.2%) in general surgery, and 42 801 procedures (18.1%) in vascular surgery. The mFI was associated with readmission (odds ratio [OR], 1.11; 95% CI, 1.10-1.12; R2 = 10.3%; C statistic, 0.71). Unadjusted rates of overall 30-day readmission (26 262 [11.1%]), postdischarge emergency department visit (34 204 [14.4%]), any predischarge (13 855 [5.9%]) or postdischarge (14 836 [6.3%]) complication, and postdischarge mortality (1985 [0.8%]) varied by frailty in a dose-dependent fashion. In analysis by individual mFI components using Harrell ranking, impaired functional status, identified as nonindependent functional status (OR, 1.16; 95% CI, 1.11-1.21; P < .01) or having a residual deficit from a prior cerebrovascular accident (OR, 1.17; 95% CI, 1.11-1.22; P < .01), contributed most to the ability of the mFI to anticipate readmission compared with the other components. Acutely impaired sensorium (OR, 1.12; 95% CI, 0.99-1.27; P = .08) and history of a myocardial infarction within 6 months (OR, 0.93; 95% CI, 0.81-1.06; P = .28) were not significantly associated with readmission.

Conclusions and relevance: The mFI is associated with poor surgical outcomes, including readmission, primarily due to impaired functional status. Targeting potentially modifiable aspects of frailty preoperatively, such as improving functional status, may improve perioperative outcomes and decrease readmissions.

Figure 1.. Population Prevalence of Frailty Components

The most common Modified Frailty Index comorbidities include hypertension requiring medication and history of diabetes requiring treatment with oral antihyperglycemics or insulin. CABG indicates coronary artery bypass graft; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; MI, myocardial infraction; PCI, percutaneous coronary intervention; and TIA, transient ischemic attack.

Figure 2.. Observed 30-Day Postoperative Outcomes by Frailty Component Burden

No patients in this cohort experienced more than 9 frailty components (10 and 11 not pictured). Observed rates of 30-day postoperative outcomes, including unplanned readmission, emergency department (ED) use, any predischarge or postdischarge complication, and postdischarge mortality, increase as frailty components accumulate. The Modified Frailty Index and its components are explained in the Variables subsection of the Methods section.