  The ubiquity of smartphone usage in many people's lives make it a rich source
of information about a person's mental and cognitive state. In this work we
analyze 12 weeks of phone usage data from 113 older adults, 31 with diagnosed
cognitive impairment and 82 without. We develop structured models of users'
smartphone interactions to reveal differences in phone usage patterns between
people with and without cognitive impairment. In particular, we focus on
inferring specific types of phone usage sessions that are predictive of
cognitive impairment. Our model achieves an AUROC of 0.79 when discriminating
between healthy and symptomatic subjects, and its interpretability enables
novel insights into which aspects of phone usage strongly relate with cognitive
health in our dataset.
