Resilience, Survival and Functional Independence in Older Adults Facing Critical Illness

Background
Older adults surviving critical illness often experience new or worsening functional impairments. Modifiable positive psychological constructs, like resilience, may mitigate post-intensive care morbidity.

Research Question
Is pre-ICU resilience associated with: (1) post-ICU survival; (2) the drop in post-ICU functional independence; and (3) a lesser decline of independence before versus after the ICU?

Study Design and Methods
We performed a retrospective cohort study using Medicare-linked Health and Retirement Study surveys from 2006-2018. We included Older adults ≥65 years admitted to an ICU. We calculated resilience before ICU admission. The resilience measure was defined from the Simplified Resilience Score which was previously adapted and validated for the Health and Retirement Study. Resilience was scored using the leave-behind survey normalized to 0 (lowest resilience) to 12 (highest resilience) point scale. Outcomes were survival and probability of functional independence. We modeled survival using Gompertz models and independence using joint survival models adjusting for sociodemographic and clinical variables. We estimated average marginal effects to determine independence probabilities.

Results
Across 3,409 patients ≥65 years old admitted to ICUs, pre-existing frailty (30.5%) and cognitive impairment (24.3%) were common. Most patients were previously independent (82.7%). Mechanical ventilation occurred in 14.8% and sepsis in 43.2%. Highest versus lowest resilience had lower risk of post-ICU mortality (aHR 0.81 95% CI [0.70, 0.94]). Higher resilience was associated with greater likelihood in post-ICU independence (estimated probability of independence 5 years post-ICU in highest-to-lowest resilience: 0.53 CI 95% [0.33, 0.74], 0.47 [0.26, 0.68], 0.49 [0.28, 0.70], 0.36 [0.17, 0.55] p<0.01). Resilience was not associated with a difference in the drop of independence across resilience groups, nor a difference in declines of independence post-ICU.

Interpretation
ICU survivors with higher resilience had increased rates of survival and functional independence, though the slope of functional decline did not differ by resilience group pre- to post-ICU.