# In a prospective population-based study, the degree of mobility impairment during hospitalisation is associated with higher degrees of frailty

## TL;DR

Hospital immobility is linked to increased frailty in older adults, suggesting that mobility during hospital stays could influence health outcomes.

## Contribution

This study identifies immobility during hospitalization as a modifiable risk factor for increased frailty in older patients.

## Key findings

- High immobility burden during hospitalization is associated with increased frailty scores.
- Immobility burden remains a significant predictor of frailty even when controlling for initial mobility and illness severity.
- High immobility burden is also prognostic of subsequent death.

## Abstract

Hospitals pose a high risk for frailty to develop or accelerate. Still, few community-based cohort studies follow patients before, during, and after hospitalisation. We investigated the degree of immobility during hospitalisation and its impact on subsequent frailty.

In a prospective population-based cohort of individuals aged ≥ 70 from a London UK borough, we performed comprehensive community assessments at baseline and after two years. At each hospitalisation, we measured daily mobility and other clinical variables. Acute immobility burden, a summative level of poor mobility for all hospitalisations, was calculated for each participant and operationalized as low/high based on the population median. A frailty index was calculated for all participants during baseline and follow-up assessments. We estimated the effect of these exposures on follow-up frailty index scores using linear regression.

We included 1177 participants. Those admitted (N = 114) were assessed over 1999 bed-days. The degree of baseline frailty had the largest association with subsequent frailty. However, a high immobility burden during hospitalisation was consistently related to additional increases in frailty (low burden: β = 0.02 per unit increase in FI (95%CI: -0.002-0.04), high burden: β = 0.07, (95%CI: 0.041-0.10)). Immobility burden remained associated with subsequent frailty even when limiting the analysis to: those who were independently mobile; the first seven days of hospitalisation; and accounting for illness severity. High immobility burden was prognostic of subsequent death.

The degree of immobility during hospitalisation, a potentially modifiable risk factor, may determine whether hospitalisation contributes to increasing frailty.

The online version contains supplementary material available at 10.1007/s40520-025-03178-2.