The relationships between apathy, depression and functional impairment in questionable dementia (QD) and Alzheimer's disease (AD) are complex. This study aimed to explore the interactions between severity of apathy, depression and functional performance; and to investigate the effects of apathy alone, depression alone and coexistence of apathy and depression on the functional performance in subjects with QD and AD.
One hundred ninety-five subjects with QD and 96 subjects with mild AD were recruited. Apathy and depression were rated using the Neuropsychiatric Inventory and functional disability was measured using the Disability Assessment for Dementia (DAD).
Severity of apathy and depression symptoms were associated with poorer functional performance in QD and apathy was associated with poorer functional performance in AD. In QD, subjects with apathy, depression, or coexistence of apathy and depression had poorer functional performance than those with neither apathy nor depression. The coexistence of apathy and depression did not produce more severe functional disability than apathy alone or depression alone. In AD, subjects with apathy had poorer functional performance than those without apathy. Depression in the absence of apathy was not associated with more severe functional disability.
Apathy and depression symptoms are common in the early course of AD. Apathy and depression had different effects on functional performances in the subjects with QD from those with AD. Copyright © 2006 John Wiley & Sons, Ltd.