Utility of Actimetry to Detect Apathy in Old-Age Depression: a Pilot Study

Apathy is a promising marker of dementia conversion in old-age depression. However, the classical definition of apathy, as a lack of motivation, does not satisfy the criteria of objectivity and validity. The direct measure of subject activity by actigraphy might provide more promising results to characterize patients. In this paper, we evaluate the utility of actimetry to distinguish the activity of apathetic depressed elderly from non-apathetic depressed ones and control population. To this end, six features were extracted to characterize daily activity measured by a wrist-worn actimeter. These features present a statistical significance to discriminate between different groups. Furthermore, the results showed a linear relationship between the physical activity and the clinical severity of apathy. This pilot study suggests that the combination of motion signals parameters provides a promising diagnostic utility in apathetic depressed elderly, with an objective to complete current data with a larger cohort of participants.