Delirium Mediates Incidence of Hospital-Associated Disability Among Older Adults.

OBJECTIVE: To examine whether delirium predicts occurrence of hospital-associated disability (HAD), or functional decline after admission, among hospitalized older adults. DESIGN: Retrospective cross-sectional study. SETTING AND PARTICIPANTS: General inpatient (non-ICU) units of a large regional Southeastern US academic medical center, involving 33,111 older adults ≥65 years of age admitted from January 1, 2015, to December 31, 2019. METHODS: Delirium was defined as a score ≥2 on the Nursing Delirium Screening Scale (NuDESC) during hospital admission. HAD was defined as a decline on the Katz Activities of Daily Living (ADL) scale from hospital admission to discharge. Generalized linear mixed models were used to examine the association between delirium and HAD, adjusting for covariates and repeated observations with multiple admissions. We performed multivariate and mediation analyses to examine strength and direction of association between delirium and HAD. RESULTS: One-fifth (21.6%) of older adults developed HAD during hospitalization and experienced higher delirium rates compared to those not developing HAD (24.3% vs 14.3%, P < .001). Age, presence of delirium, Elixhauser Comorbidity Score, admission cognitive status, admission ADL function, and length of stay were associated (all P < .001) with incident HAD. Mediational analyses found 46.7% of the effect of dementia and 16.7% of the effect of comorbidity was due to delirium (P < .001). CONCLUSIONS AND IMPLICATIONS: Delirium significantly increased the likelihood of HAD within a multivariate predictor model that included comorbidity, demographics, and length of stay. For dementia and comorbidity, mediation analysis showed a significant portion of their effect attributable to delirium. Overall, these findings suggest that reducing delirium rates may diminish HAD rates.