Prevalence of cognitive impairment in older medical inpatients: A systematic review and meta-analysis

Cognitive impairment is common among older adults and is associated with adverse outcomes such as prolonged hospital stays and increased mortality. Many of the medical inpatients subsequently undergo surgical procedures, where cognitive impairment is known to influence perioperative risk, anesthetic management, and postoperative outcomes. No meta-analysis has comprehensively synthesized global data specific to cognitive impairment among medically hospitalized patients. We aimed to determine the global prevalence of cognitive impairment in older medical inpatients and explore variations by assessment method and region.

We searched MEDLINE (Ovid), Embase, Cochrane Central, Cochrane Database of Systematic Reviews, and PsycINFO for relevant articles. We included patients ≥ 60 years old admitted to hospitals and studies examining prevalence of cognitive impairment. Excluded were elective surgical patients and non-hospital settings. Cognition was assessed by validated cognitive assessment tools, diagnostic instruments, or prior diagnosis. The primary outcome was the pooled prevalence of cognitive impairment in older patients admitted to hospitals. Subgroup analyses were conducted based on cognitive assessment tools, geographic regions, study type, and sample size.

Fifty-six studies (n = 62,853) were included. Mean age was 79.8 ± 7.7 years with 56% female. Meta-analysis revealed substantial variability across studies, with pooled prevalence estimates demonstrating high heterogeneity. The prevalence of newly suspected cognitive impairment/dementia using the Diagnostic and Statistical Manual of Mental Disorders and/or validated screening tools was 38% (95% CI: 33%-42%). The prevalence of pre-diagnosed cognitive impairment/dementia documented from medical records was 24% (95% CI: 19%-29%). The prevalence of dementia was higher in Western countries than Eastern countries [41% (95% CI: 32%-50%) vs 27% (95% CI: 21%-33%)].

Cognitive impairment is prevalent among older medical inpatients. The variability in prevalence was dependent on assessment method and geographic region. Given the substantial heterogeneity and low to very low certainty of the evidence available, these prevalence estimates should be interpreted with caution.