Validation of Smartphone-Derived Digital Phenotypes for Cognitive Assessment in Older Adults

Abstract

As the global burden of dementia continues to plague our healthcare system, efficient, objective, and sensitive tools to characterize cognition and detect underlying neurodegenerative disease increasingly are needed. Digital phenotyping relies on passive, continuous collection of smartphone sensor data during everyday life to measure activities, behaviors, and mood. The present study explored the feasibility, acceptability, and validity of a digital phenotyping protocol as a novel method for characterizing cognition and function among a heterogeneous group of older adults. Validation analyses were based on a recently proposed conceptual model explaining activity level and variability as a function of cognitive ability level. Exploratory analyses aimed to examine and account for a range of participant and environmental factors that may be associated with digital phenotyping data. A total of 22 participants ages 65 - 81 years with either healthy cognition or mild cognitive impairment (MCI) used their own personal smartphones naturally during a four-week study period while a secure software application unobtrusively and continuously obtained Global Positioning System (GPS)-based movement trajectories. Participants completed gold-standard neuropsychological measures and questionnaires of everyday function, mood, and mobility habits at a baseline visit intended to evaluate construct validity. In-depth informed consent and a comprehension of consent quiz also were administered at baseline to inform feasibility of explaining digital phenotyping study procedures to older adults. Debriefing questionnaires were completed at the end of the study period, including questions pertaining to acceptability. Correlation analyses showed that measures of GPS activity and variability were positively associated with validators of cognition, everyday function, mood, and mobility habits. Potential confounding factors included season of study participation, unexpected health changes, and highest lifetime household annual income, whereas participant demographics such as education, sex, and race were not significantly associated with GPS features. Metrics on study withdrawal, comprehension of consent, and satisfaction ratings at study completion revealed good feasibility and acceptability. In sum, digital phenotyping shows promise as a feasible, acceptable, and potentially valid method to efficiently and objectively assess cognition, function, and mood in a cohort of older adults. Future studies will benefit from incorporating these preliminary findings and testing predictions in larger, more diverse cohorts both cross-sectionally and over time in longitudinal designs.