Relationship between cognitive status at admission and incident delirium in older medical inpatients.

To evaluate the relationship between cognitive status and incident delirium, 291 geriatric patients on internal medicine wards were evaluated on admission with the Mini-Mental State Examination (MMSE) and Confusion Assessment Method-Spanish. Those with incident delirium were assessed using the Delirium Rating Scale-Revised-98 (DRS-R98). Delirium incidence was 11.7%, and 82 patients (28.2%) had cognitive deficits on MMSE. As cognitive impairment worsened, the risk for delirium increased linearly, and for each unit of MMSE worsening the DRS-R98 severity score worsened 0.4 points (F=5.39, df=1, p=0.027). Optimal MMSE cutoff score from receiver-operating characteristic curve analysis was 24.5. Even mild cognitive deficits increase delirium risk and severity.