Prevalence and risk factors of subsyndromal delirium in ICU: A systematic review and meta-analysis

Objective: To systematically assess the prevalence and risk factors for subsyndromal delirium (SSD) in the intensive care unit. Design: A systematic review and meta-analysis. Methodology: This systematic review and meta-analysis was conducted in eight databases, including PubMed, Web of Science, Ovid, Scopus, China Knowledge Resource Integrated Database, Wanfang Database, Weipu Database and Chinese Biomedical Database. All original observational studies of subsyndromal delirium in the ICU were included, with languages limited to English and Chinese. The methodological quality was assessed by the Newcastle-Ottawa Scale and the Agency for Healthcare Research and Quality recommendation checklist. Meta-analysis was performed using Stata software (version 18.0). Result: A total of 27 studies involving 7,286 participants were included in this review. The pooled prevalence of SSD was 32.4 % (95 %CI: 27.1 %-37.7 %). Fourteen studies reported 34 independent risk factors, and the following ten factors were significantly associated with SSD: older age, higher Acute Physiology and Chronic Health Evaluation II (APACHE II) score, lower Mini-mental Status Examination (MMSE) score, pain, mechanical ventilation, hypoproteinemia, blood transfusion, longer ICU stay, infection, and physical restraint. Conclusion: We conducted a systematic review and meta-analysis to evaluate the prevalence of SSD in the ICU and identified 10 risk factors associated with SSD. However, the studies have significant heterogeneity, future research should be conducted in multicenter with large samples to strengthen the current evidence. Implications for clinical practice: Subsyndromal delirium is a frequently occurring adverse event in the ICU, so it is recommended that clinicians and nurses incorporate the assessment of SSD into their daily routine. In this study, we also identified ten risk factors associated with SSD, and some of which could be modified or intervened. These findings provide a basis for ICU medical staff to identify patients at high risk of SSD and then implement individualized interventions to reduce the prevalence of SSD.