Previous-night subjective sleep quality and new-onset subsyndromal delirium in adults aged 60 years and older with acute ischemic stroke: a prospective cohort study

Background Subsyndromal delirium (SSD) is a subthreshold state within the delirium spectrum and is associated with adverse outcomes after ischemic stroke. Whether repeated sleep assessment can provide time-sensitive information for focused reassessment remains unclear. We examined the association between previous-night subjective sleep quality and new-onset SSD in adults aged 60 years and older hospitalized with acute ischemic stroke. Methods This single-center prospective cohort study enrolled 540 adults aged 60 years or older who screened negative for SSD and delirium at admission. The Richards-Campbell Sleep Questionnaire (RCSQ) was administered each morning for 7 days, followed by three scheduled Confusion Assessment Method (CAM) assessments later the same day and event-triggered reassessment when new or fluctuating abnormalities were reported. First-detected SSD was the primary outcome and direct delirium without prior SSD was treated as a competing event. The primary analysis included 526 participants. A cause-specific discrete-time hazard model estimated the association between each 10-point lower previous-night RCSQ score and subsequent SSD. Results Among 526 participants, 171 (32.5%) developed SSD, 138 (80.7%) of whom were first detected during the first 2 assessment days; 9 participants developed delirium without prior SSD. The primary time model included 170 temporally valid SSD events in 2,766 daily observation periods. After prespecified adjustment, each 10-point lower RCSQ score was associated with a higher cause-specific hazard of SSD (hazard ratio 2.99, 95% confidence interval 2.37–3.76). Sensitivity analyses using alternative SSD definitions, an additional lag, and all 540 participants yielded associations in the same direction. Conclusion Lower previous-night subjective RCSQ scores were associated with SSD first detected later the same day. Repeated RCSQ assessment may provide additional context for cognitive monitoring, but its value in guiding targeted reassessment requires prospective evaluation.