Joint impact of dementia and frailty on healthcare utilisation and outcomes: a retrospective cohort study of long-stay home care recipients

Objectives: To examine the associations between dementia and 1-year health outcomes (urgent hospitalisation, long-term care (LTC) admission, mortality) among long-stay home care recipients and the extent to which these associations vary by clients' frailty level.

Design: A retrospective cohort study using linked clinical and health administrative databases.

Setting: Home care in Ontario, Canada.

Participants: Long-stay (≥60 days) care clients (n=153 125) aged ≥50 years assessed between April 2014 and March 2015.

Main outcome measures: Dementia was ascertained with a validated administrative data algorithm and frailty with a 66-item frailty index (FI) based on a previously validated FI derived from the clinical assessment. We examined associations between dementia, FI and their interactions, with 1-year outcomes using multivariable Fine-Gray competing risk (urgent hospitalisation and LTC admission) and Cox proportional hazards (mortality) models.

Results: Clients with dementia (vs without) were older (mean±SD, 83.3±7.9 vs 78.9±11.3 years, p<0.001) and more likely to be frail (30.3% vs 24.2%, p<0.001). In models adjusted for FI (as a continuous variable) and other confounders, clients with dementia showed a lower incidence of urgent hospitalisation (adjusted subdistribution HR (sHR)=0.84, 95% CI: 0.83 to 0.86) and mortality rate (adjusted HR=0.87, 95% CI: 0.84 to 0.89) but higher incidence of LTC admission (adjusted sHR=2.60, 95% CI: 2.53 to 2.67). The impact of dementia on LTC admission and mortality was significantly modified by clients' FI (p<0.001 interaction terms), showing a lower magnitude of association (ie, attenuated positive (for LTC admission) and negative (for mortality) association) with increasing frailty.

Conclusions: The strength of associations between dementia and LTC admission and death (but not urgent hospitalisation) among home care recipients was significantly modified by their frailty status. Understanding the public health impact of dementia requires consideration of frailty levels among older populations, including those with and without dementia and varying degrees of multimorbidity.