Game-Based Cognitive Aging Assessment: Toward a Digital Biomarker of Cognitive Health.

Introduction: Cognitive performance declines with age and predicts important life outcomes, making it a promising - yet underutilized - biomarker of aging. In this study, we aimed to establish the feasibility and value of game-based digital biomarkers of cognitive aging using data from a home-based cognitive assessment game. Methods: Participants (N = 871; age 18-75) completed Tunnel Runner, a 20-25 min cognitive game measuring reaction speed, response inhibition, interference control, response-rule switching, and decision-making. To assess the game's out-of-sample predictive accuracy, we trained machine learning models to predict participants' chronological age based on 17 game-based cognitive metrics and evaluated their performance using nested cross-validation. Cognitive aging scores were calculated as out-of-sample prediction errors from the best-performing model, and then adjusted for age-dependence using generalized additive models. These aging scores were then considered alongside three other variables: depression, ADHD, and gamer identity. Results: The best-performing model, stacked ensemble from the automated machine learning framework AutoGluon, predicted out-of-sample chronological age with a mean absolute error of 6.97 years, a correlation of 0.626, and concordance of 0.698. No evidence of bias in predictive accuracy was found for gender or gaming identity. Prediction patterns and cognitive aging values met several expectations based on previous research: reduced cognitive aging in participants with self-reported ADHD, negative association between cognitive aging and gamer identity, and limited predictive differentiation under age 30. Findings regarding self-reported depression were inconclusive, though consistent with prior work. Conclusion: Game-based assessment can produce accessible digital biomarkers of cognitive aging that reflect meaningful individual differences. This approach enables scalable and low-burden cognitive aging assessment, with potential applications for early detection of cognitive decline, longitudinal tracking, and intervention evaluation.