To explore the bidirectional relationship between depression symptoms and physical functional impairment trajectories in Chinese elderly individuals.

Utilizing data from four waves of the China Health and Retirement Longitudinal Study (CHARLS) conducted in 2011, 2013, 2015, and 2018, we employed group-based trajectory modeling to identify distinct trajectory groups for depression symptoms and physical functional impairment among the elderly. A dual trajectory model was then used to assess the degree of association between these trajectory groups.

The group-based trajectory model categorized depression symptoms into four groups: consistently low depression symptoms, decreasing depression symptoms, increasing depression symptoms, and consistently high depression symptoms. Physical functional impairment was classified into four groups: no physical functional impairment, worsening physical functional impairment, improving physical functional impairment, and high physical functional impairment. Dual trajectory analysis revealed that 44.86% of individuals in the decreasing depression symptoms group followed the improving physical functional impairment trajectory; conversely, 37.58% of individuals in the increasing depression symptoms group followed the worsening physical functional impairment trajectory. Among those in the worsening physical functional impairment group, 47.8% followed the increasing depression symptoms trajectory, while 41.9% of individuals in the improving physical functional impairment group followed the decreasing depression symptoms trajectory.

In most cases, there is a positive correlation between the trajectories of depression symptoms and physical functional impairment. A decrease in depression symptoms is typically associated with an improvement in physical functional impairment, while an increase in depression symptoms corresponds with a worsening of physical functional impairment, and vice versa.