Mild behavioral impairment and risk of dementia: a prospective cohort study of 358 patients.

Background: Mild cognitive impairment (MCI) is a transitional state between normal aging and dementia, at least for some patients. Behavioral symptoms in MCI are associated with a higher risk of dementia, but their association with dementia risk in patients without MCI is unknown. Mild behavioral impairment (MBI) refers to a late-life syndrome with prominent psychiatric and related behavioral symptoms in the absence of prominent cognitive symptoms that may also be a dementia prodrome. This study sought to compare MCI and MBI patients and to estimate the risk of dementia development in these 2 groups.

Method: Between January 2001 and January 2006, a consecutive series of 358 elderly (>or= 65 years old) patients (239 with MCI and 119 with MBI) presenting to an outpatient general hospital specialty clinic were followed for up to 5 years until conversion to dementia or censoring.

Results: Thirty-four percent of MCI patients and over 70% of patients with MBI developed dementia (log-rank p = .011). MBI patients without cognitive symptoms were more likely to develop dementia (log-rank p < .001). MBI patients were more likely to develop frontotemporal dementia (FTD) than dementia of the Alzheimer's type (DAT).

Conclusion: MBI appears to be a transitional state between normal aging and dementia. MBI (specifically in those without cognitive symptoms) may confer a higher risk for dementia than MCI, and it is very likely an FTD prodrome in many cases. These findings have implications for the early detection, prevention, and treatment of patients with dementia in late life, by focusing the attention of researchers on the emergence of new behavioral symptoms.