<qa>  What is the main cause of the need for increasing levels of care for the patient with AlzheimerAgitation and other behavioral disturbances are a main cause in the need for increasing levels of care for the patient with Alzheimers disease AD. And while the pathology of dementia has been studied in great detail, the etiology is considered multi-factorial. The hypothesis behind this clinical study is that the presence of the apo lipoprotein E4 APO E4 allele will serve to predict which patients with late on-set AD are at greater risk to develop agitation. 