Abstract

OBJECTIVES: To describe the motoric subtypes of delirium in critically ill patients and compare patients aged 65 and older with a younger cohort. DESIGN: Prospective cohort study. SETTING: The medical intensive care unit (MICU) of a tertiary care academic medical center. PARTICIPANTS: Six hundred fourteen MICU patients admitted during a process improvement initiative to monitor levels of sedation and delirium. MEASUREMENTS: MICU nursing staff assessed delirium and level of consciousness in all MICU patients at least once per 12‐hour shift using the Confusion Assessment Method for the Intensive Care Unit and the Richmond Agitation‐Sedation Scale. Delirium episodes were categorized as hypoactive, hyperactive, and mixed type. RESULTS: Delirium was detected in 112 of 156 (71.8%) subjects aged 65 and older and 263 of 458 (57.4%) subjects younger than 65. Mixed type was most common (54.9%), followed by hypoactive delirium (43.5%) and purely hyperactive delirium (1.6%). Patients aged 65 and older experienced hypoactive delirium at a greater rate than younger patients (41.0% vs 21.6%, P <.001) and never experienced hyperactive delirium. Older age was strongly and independently associated with hypoactive delirium (adjusted odds ratio=3.0, 95% confidence interval=1.7–5.3), compared with no delirium in a model that adjusted for other important determinants of delirium including severity of illness, sedative medication use, and ventilation status. CONCLUSION: Older age is a strong predictor of hypoactive delirium in MICU patients, and this motoric subtype of delirium may be missed in the absence of active monitoring.