Screen time modalities and neurocognition in older adults: multi-cohort and Mendelian randomization evidence

Abstract Screen-time activities may have divergent cognitive implications in older adults. Among 8996 participants from four aging cohorts, each additional hour/day of television viewing was associated with lower global cognition ( β range, −0.047 to −0.034), mainly reflected in memory-related outcomes and largely linear inverse dose–response patterns. Conversely, computer use was associated with higher global cognition ( β range, 0.047 to 0.076), especially processing speed and delayed recall, with clearest positive associations at low-to-moderate use. Mendelian randomization analyses supported these opposing patterns: genetically predicted television viewing time was associated with poorer cognitive performance and lower left insula volume, with two-step MR suggesting 14.8% mediation through the left insula and exploratory signals of weaker insula/anterior cingulate–frontal control connectivity. Genetically predicted computer use time was associated with better cognitive performance and exploratory signals of higher parietal-frontal connectivity. These findings support activity-based screen-time assessment for cognitive risk stratification and targeted digital health interventions in cognitive aging.