 Sleep patterns normally change with age. Sleepwake cycles appear to be compromised in people suffering from dementia. Most research involving sleep in dementia has involved community dwelling or nursing home residents. Relatively little is known about the sleep patterns of patients with dementia who develop acute behavioral and psychiatric symptoms and necessitate hospitalization. The relationship between sleep disturbances in these patients and behavioralpsychiatric symptoms is also insufficiently studied. The current study will examine these two sets of data sleepwake cycles and clinical symptoms in a population of elderly subjects with Dementia of the Alzheimers type DAT or vascular dementia VD during their hospitalization period. We will compare the sleep outcome measures primarily sleep efficiency and clinical outcome measures in subjects treated with Zolpidem CR or Placebo. We will utilize a double-blind, randomized, placebo-controlled design to test our hypothesis that targeting sleep disturbances in hospitalized elderly subjects with DAT or VD leads to improvement in sleep and clinical outcomes. 