The role of illness acuity on the association between frailty and mortality in emergency department patients referred to internal medicine

Background: we investigated whether two frailty tools predicted mortality among emergency department (ED) patients referred to internal medicine and how the level of illness acuity influenced any association between frailty and mortality. Methods: two tools, embedded in a Comprehensive Geriatric Assessment (CGA), were the clinical frailty scale (CFS) and a 57-item deficit accumulation frailty index (FI-CGA). Illness acuity was assessed using the Canadian Triage and Acuity Scale (CTAS). We examined all-cause 30-day and 6-month mortality and time to death. Results: in 808 ED patients (mean age ± SD 80.8 ± 8.8, 54.4% female), the mean FI-CGA score was 0.44 ± 0.14, and the CFS was 5.6 ± 1.6. A minority (307; 38%) were classified as having high acuity (CTAS: 1–2). The 30-day mortality rate was 17%; this increased to 34% at 6 months. Compared to well patients with low acuity, the risk of 30-day mortality was 22.5 times (95% CI: 9.35–62.12) higher for severely frail patients with high acuity; 53% of people with very severe frailty (CFS = 8) and high acuity died within 30 days. When acuity was low, the risk for 30-day mortality was significantly higher only among those with very high levels of frailty (CFS 7–9, FI-CGA > 0.5). When acuity was high, even lower levels of frailty (CFS 5–6, FI-CGA 0.4–0.5) were associated with higher 30-day mortality. Conclusions: across levels of frailty, higher acuity increased mortality risk. When acuity was low, the risk was significant only when the degree of frailty was high, whereas when acuity was high, even lower levels of frailty were associated with greater mortality risk.