# Temporal Dynamics and Bidirectional Longitudinal Association Between Physical Function and Depressive Symptoms in Older Adults

## TL;DR

This study finds that physical function decline and depressive symptoms in older adults are linked in both directions over time, suggesting they influence each other.

## Contribution

The study reveals a bidirectional longitudinal association between physical function and depressive symptoms in older adults using robust statistical models.

## Key findings

- Poor physical function increases the odds of developing depressive symptoms by 81%.
- Depressive symptoms increase the odds of reduced physical function by 70%.
- Bidirectional associations were confirmed using cross-lagged panel models across follow-up waves.

## Abstract

Physical function decline and depression are major challenges of the rapidly growing older population. This longitudinal study aimed to investigate the bidirectional longitudinal association between physical function and depressive symptoms, which are poorly understood in older adults.

We utilised data from the ASPirin in Reducing Events in the Elderly (ASPREE) clinical trial and extended follow‐up cohort between 2010 and 2022. The presence of depressive symptoms was defined as a score of ≥ 8 on the Center for Epidemiologic Studies Depression 10‐item scale. Physical function was assessed using gait speed for physical performance and handgrip strength for muscle strength. Gait speed and handgrip strength were categorised using the European Working Group on Sarcopenia in Older People (EWGSOP2) cut‐off points. The bidirectional association between physical function and depressive symptoms was estimated using generalised estimating equations models. The robustness of the longitudinal bidirectional relationship was assessed using random‐intercept cross‐lagged panel models.

Among 19 114 ASPREE participants, 15 854 (56% females) older adults (mean age 75 years) were included in the analysis. During a median follow‐up of 8.4 years, participants with combined poor physical performance and weak muscle strength had 81% higher odds of developing depressive symptoms compared to those with good performance and strength (OR = 1.81, 95% CI: 1.55–2.11). Conversely, participants with depressive symptoms had 70% higher odds of reduced physical function (combined poor physical performance and weak muscle strength) compared to those with no depressive symptoms (OR = 1.70, 95% CI: 1.61–1.80). The random‐intercept cross‐lagged panel models verified the bidirectional longitudinal associations between physical function and depressive symptoms across the follow‐up waves.

Reduced physical function and depressive symptoms are associated bidirectionally over time of a similar magnitude. Understanding this reciprocal association is crucial for developing effective prevention and treatment strategies for physical and mental health conditions.