Research evaluation and diagnosis of possible Alzheimer's disease over the last two decades: II.

OBJECTIVE: To describe the experience of a research clinic diagnosing possible AD during the last two decades.
BACKGROUND: The National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for possible AD are generally used to indicate that a patient has AD in association with another disease process that could by itself cause dementia. There are no studies describing how these criteria should be applied, and there are no descriptions of functional and cognitive progression or survival in possible AD.
METHODS: The authors examined the clinical characteristics of 267 patients diagnosed with possible AD at the AD Research Center of Pittsburgh from 1983 to 2000 and the likelihood of arriving at four endpoints: Mini-Mental State Examination score of </= 9, Blessed Dementia Rating Scale for activities of daily living score of >/= 12, nursing home admission, and death.
RESULTS: The possible AD classification has been simplified in six categories: possible AD with cerebrovascular disease (CVD) (69%), with history of alcohol abuse (15%), with history of depression (7%), with thyroid disease (4%), with history of head trauma (6%), with vitamin B12 deficiency (6%), and with other disease process that may have affected the clinical presentation of AD (4%). The presence of CVD, history of alcohol abuse, and history of depression concomitant with the onset of dementia were associated with time to death. Neither thyroid disease, history of head trauma, nor vitamin B12 deficiency were associated with any of the four endpoints.
CONCLUSION: This cohort showed that comorbid conditions that can affect cognition delineate clearly defined subgroups in AD. The presence of environmental or other brain disorders sufficient to produce dementia appears to affect physical survival in patients with AD, but not functional and cognitive decline or institutionalization.