Incidence and Prevalence of Delirium Subtypes in an Adult ICU: A Systematic Review and Meta-Analysis*

Use systematic review and meta-analytic methodology to estimate the pooled incidence, prevalence, and proportion of delirium cases for each delirium subtype (hypoactive, hyperactive, and mixed) in an adult ICU population.We conducted a search of the MEDLINE, EMBASE, CINAHL, SCOPUS, Web of Science, and PsycINFO databases following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses standards from database inception until October 22, 2017, with no restrictions.We included original research conducted in adults admitted to any medical, surgical, or speciality ICU that reported incidence or prevalence estimates of delirium according to delirium subtype.Data were extracted on sample size, population demographics, condition information, and reported delirium estimates.Forty-eight studies (27,342 patients; 4,550 with delirium) with an overall pooled prevalence of 31% (95% CI, 24-41; I = 99%) met inclusion criteria. The pooled incidence (n = 18 studies) of delirium subtypes were hyperactive (4% [95% CI, 2-6]; I = 92%]), hypoactive (11% [95% CI, 8-17; I = 97%]), and mixed (7% [95% CI, 4-11; I = 97%]). The pooled prevalence (n = 31 studies) of delirium subtypes were hyperactive (4% [95% CI, 3-6; I = 94%]), hypoactive (17% [95% CI, 13-22; I = 97%]), and mixed (10% [95% CI, 6-16; I = 99%]). The pooled prevalence of hypoactive delirium in study populations with a similarly high severity of illness or mechanically ventilated was higher (severity of illness: 29% [95% CI, 18-46%; I = 95%], 100% mechanically ventilated: 35% [95% CI, 23-55%; I = 93%]) compared with the pooled prevalence of hypoactive delirium.Despite significant heterogeneity between studies, these data show the majority of delirious ICU patients to have hypoactive delirium, a finding with potential monitoring, management, and prognostic implications. The prevalence of hypoactive delirium varies between-study populations and is higher in patients with greater severity of illness.