Do JST-IC Trajectories Truly Capture Aging Processes? A Need to Reconsider What the Trajectories Represent.

JST-IC trajectory patterns may reflect enduring life-course capacities rather than aging-related decline.

• The authors argue that trajectory patterns may represent 'mixed trait-change constructs' rather than pure aging processes.
• Cognitive reserve is identified as a factor shaping the observed trajectory patterns.
• The letter questions whether JST-IC-based trajectories 'primarily reflect aging-related decline or enduring life-course capacities and contextual adaptation.'
• This distinction has 'important implications for interpretation and intervention.'

Digital literacy is identified as a factor that may shape JST-IC trajectory patterns.

• Digital literacy is listed alongside cognitive reserve and cohort-specific exposures as a construct potentially influencing observed trajectories.
• The authors suggest these factors contribute to the 'mixed trait-change constructs' reflected in trajectory patterns.
• Cohort-specific exposures are also identified as contributors to trajectory pattern formation.

The authors argue that current JST-IC trajectory interpretation requires reconsideration.

• The letter calls for a 'need to reconsider what the trajectories represent.'
• The concern centers on whether trajectories capture genuine aging processes or confounded constructs.
• The authors suggest the ambiguity in what trajectories represent has implications for how interventions are designed and targeted.