The factors associated with persistent delirium, in contrast to resolved delirium, have not been studied well. The aim of our present study was to identify the factors associated with delirium resolution as measured by the Memorial Delirium Assessment Scale (MDAS) and functional improvement as measured by the Karnofsky Performance Status (KPS) scale.

All subjects were recruited from psychiatric referrals at the Memorial Sloan Kettering Cancer Center (MSKCC). The two study instruments were performed at baseline (T1), at 2–3 days (T2), and at 4–7 days (T3). Subjects with persistent delirium were compared to those with resolved delirium in respect to sociodemographic and medical variables.

Overall, 26 out of 111 patients had persistent delirium. These patients were older, predominantly male, and had more frequently preexisting comorbid dementia. Among cancer diagnoses and stage of illness, brain cancer and terminal illness contributed to persistent delirium or late response, whereas gastrointestinal cancer was associated with resolved delirium. Among etiologies, infection responded late to delirium management, usually at one week. Furthermore, delirium was more severe in patients with persistent delirium from baseline through one week. At baseline, MDAS scores were 20.1 in persistent delirium compared to 17 to 18.8 in resolved delirium (T2 and T3), and at one week of management (T3), MDAS scores were 15.2 and 4.7 to 7.4, respectively. At one week of management, persistent delirium manifested in more severe impairment in the domains of consciousness, cognition, organization, perception, psychomotor behavior, and sleep–wake cycle. In addition, persistent delirium caused more severe functional impairment.

In this delirium sample, advanced age and preexisting dementia, as well as brain cancer, terminal illness, infection, and delirium severity contributed to persistent delirium or late response, indicating a prolonged and refractory course of delirium, in addition to more severe functional impairment through one week of management.