Up to 25% of intensive care unit (ICU) survivors experience cognitive impairment comparable in severity to mild Alzheimer's disease and related dementias after hospital discharge. Older ICU survivors (ages 60 and older) are at highest risk for delirium and subsequent cognitive impairment, which contribute to higher risk for cognitive decline related to Alzheimer's disease and related dementias. Sleep and activity are essential for recovery from critical illness, yet ICU survivors experience both sleep deficiency and profound inactivity. About 75-80% of ICU patients experience circadian dysrhythmia, which contributes to cognitive decline and increases likelihood of developing Alzheimer's disease and related dementias. The scientific premises of the proposed study are: 1) a combined sleep promotion and cognitive training intervention will have synergistic effects to mitigate the risk of cognitive impairment and development of Alzheimer's disease and related dementias in older ICU survivors; and 2) chronotherapeutic timing of interventions (i.e., adjusting timing of interventions according to circadian rhythm) may improve intervention efficacy.