Investigating speech and language impairments in delirium: a preliminary case-control study
Introduction\n\nLanguage impairment is recognized as a diagnostic feature of delirium, yet there is little neuropsychological research on the nature of this dysfunction. Here we hypothesized that patients with delirium show impairments in language formation, coherence and comprehension.\n\nMethods\n\nThis was a case-control study in 45 hospitalized patients (aged 65-97 years) with delirium, dementia without delirium, or no cognitive impairment (N=15 per group). DSM-5 criteria were used for delirium. Speech was elicited during (1) structured conversational questioning, and (2) the \"Cookie Theft\" picture description task. Language comprehension was assessed through standardized verbal and written commands. Interviews were audio-recorded and transcribed.\n\nResults\n\nDelirium and dementia groups scored lower on the conversational assessment than the control group (p<0.01, moderate effect sizes (r) of 0.48 and 0.51, resp.). In the Cookie Theft task, the average length of utterances (i.e. unit of speech), indicating language productivity and fluency, distinguished patients with delirium from those with dementia (p<0.01, r=0.50) and no cognitive impairment (p<0.01, r=0.55). Patients with delirium performed worse on written comprehension tests compared to cognitively unimpaired patients (p<0.01, r=0.63), but not compared to the dementia group.\n\nConclusions\n\nProduction of spontaneous speech, word quantity, speech content and verbal and written language comprehension are impaired in delirious patients compared to cognitively unimpaired patients. Additionally, patients with delirium produced significantly less fluent speech than those with dementia. These findings have implications for how speech and language are evaluated in delirium assessments, and also for communication with patients with delirium.