240: ASSOCIATIONS BETWEEN ACTIVITY AND COGNITIVE FUNCTION IN OLDER INTENSIVE CARE UNIT SURVIVORS

Abstract

Introduction: Critically ill older adults are profoundly inactive while in ICU; therefore, activity promotion after ICU discharge is crucial for recovery. Poor cognitive function predicts institutionalization (i.e., discharge to long-term care facility). We calculated a ratio of daytime-to-nighttime activity among older ICU survivors during the early post-ICU transition period. We hypothesized that higher daytime-to-nighttime activity ratios (i.e., proportionally higher activity during daytime hours) would be associated with better cognitive function. Methods: This was a secondary analysis of pooled data from 2 primary studies of older adults (n = 44) who were functionally independent prior to hospitalization, mechanically ventilated while in ICU, and within 24-48 hours post-ICU discharge. Actigraphy recorded daytime activity (mean activity counts/minute, 06:00 AM-21:59 PM) and nighttime activity (mean activity counts/minute, 22:00 PM-05:59 AM). We calculated a daytime-to-nighttime activity ratio by dividing daytime activity by nighttime activity. The NIH Toolbox Dimensional Change Card Sort Test assessed cognitive flexibility (DCCST: fully-corrected T score). Multivariate regression examined the association between the daytime-to-nighttime activity ratio and DCCST scores, adjusting for 3 covariates (age, CAM-S delirium severity score, and NIH Toolbox Grip Strength fully-corrected T score). Results: The mean daytime-to-nighttime activity ratio was 2.10 ± 1.17 (IQR: 1.42). Ratios for 6 (13%) participants were less than 1—these participants were proportionally more active during nighttime hours, rather than daytime hours. Higher ratios were associated with better DCCST scores (β = 0.288, p = .015). Conclusions: Among this cohort of older ICU survivors, the proportion of daytime activity versus nighttime activity was considerably low, indicating severe alterations in the rest/activity and sleep/wake cycles. Higher daytime-to-nighttime activity ratios were associated with better executive function scores, suggesting that daytime inactivity and sleepiness may be an indicator of worse cognitive outcomes. Assessment and promotion of daytime activity and nighttime sleep could identify at-risk older ICU survivors during the early post-ICU transition period.