# Frailty and loneliness among community-dwelling older adults: examining reciprocal associations within a measurement burst design

## TL;DR

This study examines how frailty and loneliness are related in older adults, finding that they tend to increase together but not in a direct cause-and-effect way.

## Contribution

The study uses a measurement burst design to disentangle within- and between-person effects in the relationship between frailty and loneliness.

## Key findings

- No causal reciprocal relationship was found between frailty and loneliness over short time periods.
- Higher levels of frailty were weakly associated with higher levels of loneliness at the within-person level.
- Frailty and loneliness were significantly correlated at the between-person level in each measurement burst.

## Abstract

Previous research indicates that frailty and loneliness are interrelated. The aim of this study is to analyze their possible reciprocal relationship while disentangling between- and within-person effects. The separation of these sources of variance is vital for a better understanding of potential causal mechanisms.

Within the FRequent health Assessment In Later life (FRAIL70+) project, participants aged 70 and over completed two measurement bursts spread one year apart with seven biweekly assessments each. The final sample consisted of 426 individuals at baseline (Mage=77.0; SD = 5.4; 64.6% female). A latent curve model with structured residuals was used to examine the potential reciprocal relationship between frailty (37-item deficit accumulation approach) and loneliness (3-item UCLA scale).

No relevant cross-lagged effects over repeated 2-week periods were found between frailty and loneliness at the within-person level, but increases in frailty co-occurred with increases in loneliness. At the between-person level, higher levels of frailty correlated with higher levels of loneliness in each burst.

The findings do not support the assumption that frailty and loneliness share a causal reciprocal relationship over weeks and months. Nonetheless, higher levels of frailty were weakly associated with higher levels of loneliness at the within- and considerably associated at the between-person level, which may indicate a common source of both domains.

The online version contains supplementary material available at 10.1186/s12877-025-05808-w.