Persistent delirium in older hospital patients: an updated systematic review and meta-analysis

Introduction Persistent delirium is recognised as a substantial problem, but there are few insights into which patient groups might be particularly affected. Delirium is associated with future dementia progression. Yet whether this occurs subclinically over months and years, or persistent delirium merges into worsened dementia is not understood. Methods We adopted an identical approach to a previous systematic review, only including studies using a recognised diagnostic framework for ascertaining delirium at follow-up (persistent delirium). We applied risk of bias assessments based on Standards of Reporting of Neurological Disorders criteria. Estimates were pooled across studies using random-effects meta-analysis, and we estimated associations with age and follow-up duration using meta-regression. Results We identified 13 new cohorts, which we added to 8 from the previous systematic review (21 relevant studies reporting persistent delirium over 37 time points). Studies were mainly at low risk of bias. Pooled delirium prevalence estimates at discharge were 40% (95% CI 24% to 54%, 10 studies). Meta-regression showed variation in prevalence of persistent delirium over time (0.6% per week, 95% CI −1.2 to −0.1, p=0.02). Older study sample age was associated with higher prevalence of persistent delirium (8.8% per SD age, 95% CI 1.1% to 17%). The rate of improvement was the same regardless of age, but the overall burden was higher with older age such that 44% (95% CI 11% to 76%) of 95-year-olds would be expected to have persistent delirium at 12 months. Conclusions This systematic review emphasises the key importance of delirium as a persistent and extensive problem, particularly in the oldest-old. Addressing persistent delirium will require a whole-system, integrated approach in order to detect, follow-up and implement opportunities for recovery across all healthcare settings.