# All‐Cause Acute Illness Hospitalisations in the Preceding Two Years Are Associated With Cognitive Decline in Older Adults: The Sydney Memory and Ageing Study

## TL;DR

Hospital stays in older adults are linked to faster cognitive decline, especially recent ones, suggesting a need for better care strategies.

## Contribution

This study shows that recent all-cause hospitalizations are independently linked to accelerated cognitive decline in older adults.

## Key findings

- Recent hospitalizations were associated with a steeper decline in global cognition compared to non-recent ones.
- The cognitive decline was dose-dependent, with more days in hospital correlating with greater decline.
- The association was independent of illness severity, suggesting hospitalization itself may be a reversible risk factor.

## Abstract

Emerging evidence suggests all‐cause acute hospitalizations are associated with cognitive decline, rather than being associated only with specific inpatient contexts (surgery, critical care and delirium). This study clarifies this association in an Australian context.

This study is a secondary analysis of four biennial waves of prospective population‐based neuropsychological measures from 1026 functionally independent Sydney Memory and Ageing Study participants aged 70–90 years at baseline, and contemporaneous probabilistically‐linked hospitalization data. The outcome measures were global cognition baseline (intercept) and change (slope) and their associations with hospitalization episodes and cumulative length of stay (cLOS) variables in five consecutive 2‐year time intervals.

One thousand twenty‐six individuals had a mean age of 78.8 years, a mean Mini‐Mental State Examination score of 28.7, a mean of 3.3 hospitalizations and 18.9 days in hospital over 10 years. Mean global cognition z‐score change/year was −0.133, adjusted for age, sex and education. Hospitalizations and cLOS in the final time interval were associated with a change in slope of −0.012 global cognition z‐score/hospitalization/year (Standard Error [SE] = 0.005, p = 0.014) and −0.002 z‐score/day‐in‐hospital/year (SE = 0.001, p < 0.001). Further investigation of these associations with time‐lagged models showed that pooled recent hospitalizations were associated with accelerated cognitive decline of −0.036 change in cognition/year/episode‐of‐hospitalization (SE = 0.012, p = 0.004) and −0.008 change in cognition/year/day‐in‐hospital (SE = 0.002, p < 0.001) rather than non‐recent hospitalizations (Wald test for difference between pooled recent and non‐recent effects had p‐values of 0.011 and < 0.001 for hospitalization episodes and days respectively).

This study confirms and adds nuance to international findings that overnight hospitalization is associated with accelerated cognitive decline. This association was dose‐dependent, had a recency effect and was independent of illness severity in the case of cLOS. These findings suggest that all‐cause acute hospitalization may be a reversible risk factor for cognitive decline. This needs further clarification and the development of interventions to minimise the impact of acute illness hospitalization on cognitive trajectory. To this end, broadening the scope of acute care in the home and the prevention and treatment of neuroinflammation are priorities for further investigation.