Abstract
BACKGROUND: Delirium commonly occurs during prolonged intensive care unit (ICU) stays, yet the clinical benefit of escorted outdoor exposure for critically ill adults remains uncertain. AIM: The aim of this study was to determine whether supervised outdoor therapy is associated with reduced delirium severity among adults with ICU stays ≥ 7 days. STUDY DESIGN: We performed a single-centre, retrospective cohort study in Japan, including adults with an ICU length of stay ≥ 7 days from 1 January 2019 to 31 December 2022. Delirium was assessed twice-daily using the Intensive Care Delirium Screening Checklist (ICDSC). We evaluated (1) within-patient change from 16:00 on the day before to 16:00 on the day of the first outdoor-therapy session; (2) ICDSC score at ICU discharge comparing patients who did vs. did not receive outdoor therapy using multiple imputation integrated with propensity-score matching; and (3) dose-response using multivariable linear regression with session count, adjusting for prespecified covariates including the highest ICDSC score and psychotropics prescribed through the first session. RESULTS: Among patients (n = 391) receiving outdoor therapy, the median ICDSC score decreased from 4 to 2 on the day of the first session (p < 0.001). After propensity-score matching, the outdoor-therapy group had lower ICDSC scores at ICU discharge than matched controls (median: 3.0 [IQR 1.0-5.0] vs. 4.0 [2.0-6.0]; p = 0.013; Cliff's δ = -0.329). In the adjusted regression, a greater number of outdoor sessions was associated with a lower discharge ICDSC score (standardised β = -0.113; p = 0.025). CONCLUSIONS: Supervised outdoor therapy was associated with lower delirium severity in adults with prolonged ICU stays. These findings support the integration of outdoor exposure within multimodal delirium management while prospective multicentre studies define standardised protocols and optimal dosing. RELEVANCE TO CLINICAL PRACTICE: Incorporating brief, supervised outdoor sessions into multidisciplinary ICU workflows may provide a practical, non-pharmacological adjunct for delirium care, pending confirmation in protocolised prospective trials. TRIAL REGISTRATION: University Hospital Medical Information Network Clinical Trial Registry (UMIN-CTR) (ID: UMIN000049057; registered on 1 October 2022; https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000055872).