Cognitive reserve and digital lifestyle: Examining How technology engagement moderates age-related executive function decline in adults.

Cognitive reserve the brain's resilience to age-related decline varies widely, yet mechanisms underlying this heterogeneity are incompletely understood. This 24-month longitudinal study tracked 412 adults aged 40-75 across three waves, combining standardized executive function testing with objective smartphone usage metrics. Latent growth curve modeling within a structural equation framework examined whether digital engagement moderates executive function decline beyond traditional cognitive reserve proxies. Results showed age-related decline in executive functions (β = -0.18), with steeper decline after 60 (β = -0.29). High engagement (≥3.5 hours/day of cognitively stimulating technology) attenuated decline by 58%, specifically in cognitive flexibility (β = 0.24) and planning (β = 0.21), whereas passive consumption showed no effect. Cross-lagged analyses indicated bidirectional effects: executive function predicted subsequent engagement, and sustained engagement slowed decline. Findings highlight that quality and type of digital activity, not screen time alone, influence cognitive aging trajectories.