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Timely recognition of cognitive impairment such as Alzheimer's disease is of great significance. Many smart systems, developed to continuously monitor older adults' health and cognition, use a number of predefined measures associated with the older adults' activity in their homes. However, this approach has been demonstrated to focus on idiosyncratic nuances of the individual subjects, and thus could potentially not perform as well when tested on new subjects. In this paper, we address this problem by building proper statistical models of older adults' in-home walking speed. Using the data pertaining to 15 older adults monitored for an average period of 3 years, we used linear regression with a Gaussian likelihood to model the subjects' in-home walking speed, and we used dynamic time warping to demonstrate significant difference between the walking speed distributions of the subjects when cognitively intact and when having mild cognitive impairment (MCI). Using a simple thresholding approach of the dynamic time warping costs, we were able to detect MCI in older adults with areas under the ROC curve and the precision-recall curve of 0.906 and 0.790, respectively, using a time frame of 12 weeks.

With a globally aging population, the burden of care of cognitively impaired older adults is becoming increasingly concerning. Instances of Alzheimer's disease and other forms of dementia are becoming ever more frequent. Earlier detection of cognitive impairment offers significant benefits, but remains difficult to do in practice. In this paper, we develop statistical models of the behavior of older adults within their homes using sensor data in order to detect the early onset of cognitive decline. Specifically, we use inhomogenous Poisson processes to model the presence of subjects within different rooms throughout the day in the home using unobtrusive sensing technologies. We compare the distributions learned from cognitively intact and impaired subjects using information theoretic tools and observe statistical differences between the two populations which we believe can be used to help detect the onset of cognitive decline.