Comparing changes in late-life depressive symptoms across aging, disablement, and mortality processes

Area of Science:

• Gerontology
• Developmental Psychology
• Psychiatry

Background:

• Developmental processes are often studied in relation to time, using various metrics to understand change.
• Depressive symptoms are a significant concern in late life, with their underlying drivers requiring further investigation.

Purpose of the Study:

• To investigate whether depressive symptoms in individuals aged 70+ are primarily driven by aging, disablement, or mortality processes.
• To compare the efficiency of different time metrics (time-from-birth, time-to/from-disability-onset, time-to-death) in describing developmental trajectories of depressive symptoms.

Main Methods:

• Utilized data from four Swedish studies with 453 individuals aged 70-100+, measured over five waves every two years.
• Employed Akaike weights and compared linear and multiphase growth models to assess developmental trajectories of depressive symptoms.
• Defined disablement by the first reported impairment in Personal Activities of Daily Living (PADL).

Main Results:

• Two-phase models provided a better fit than single-phase models for depressive symptom trajectories across all time metrics.
• Time-to-death and time-to/from-disability-onset metrics offered more efficient descriptions of depressive symptom changes than time-from-birth.
• Time-to-death metrics demonstrated the best overall fit, indicating mortality processes as a key driver.

Conclusions:

• Late-life changes in depressive symptoms are significantly influenced by disablement and mortality processes, not merely chronological aging.
• Time-to-death and time-to/from-disability-onset metrics are valuable for modeling late-life depressive symptom changes and identifying risk factors.
• Researchers should consider non-age time metrics to better understand developmental changes in various constructs.