May 2024
Delirium a risk factor for death and dementia, finds Australian study
By Rebecca Jenkins
Delirium is a strong risk factor for death and incident dementia among older adults, a large Australian retrospective cohort study finds.
Observational studies had found an association between delirium and dementia, but the strength and nature of the link remained unclear, researchers wrote in the BMJ.
To further examine the association they used large-scale hospital administrative data from public and private hospitals in New South Wales between July 2001 and March 2020, extracting data for 650,590 hospital patients aged 65 years or older.
Patients with dementia at baseline were excluded, with researchers then identifying delirium and no delirium pairs by matching personal and clinical characteristics.
The study included 55,211 matched pairs with a mean age of 83.4 years, with men making up 48% of the cohort.
Collectively, 58% of patients died and 17% had a newly reported dementia diagnosis during 5.25 years of follow up. Patients with at least one episode of delirium had a 39% higher risk of death and a three times higher risk of incident dementia, the researchers reported.
There was a dose-response relationship with each additional episode of delirium increasing the risk of dementia by 20%.
In addition, the association between delirium and incident dementia seemed to be stronger among men than women.
‘These associations were observed in a large scale dataset and were robust to several tests of bias and confounding, supporting the hypothesis that delirium has a strong independent effect on dementia risk in this clinical population,’ the researchers concluded.
‘The clinical implications of delirium as a potentially modifiable risk factor for dementia are substantial.’
Study senior author Dr Emily Gordon, Geriatrician and Senior Research Fellow at the Centre for Health Services Research at the University of Queensland, Brisbane, said previous research had shown patients with delirium faced a higher risk of hospital complications, longer hospital stays and death.
‘But we, as clinicians, have also observed that many of our patients do not return to their previous level of cognitive function after an episode of delirium,’ she told Medicine Today.
‘In fact, the cognitive function of some patients just seems to keep deteriorating.’
Dr Gordon said the strength of the study findings and the dose-response effect were consistent with her clinical experience and she urged clinicians to consider delirium as a significant clinical event that carried important, long-term risks.
‘If a patient has had one episode or more of delirium, it is pertinent to monitor for cognitive decline, to optimise cognitive health (i.e. identify and treat other risk factors for dementia such as hypertension, diabetes, physical inactivity and so forth) and to be prepared to make a diagnosis of dementia if/when it occurs,’ she said.
Dr Gordon said she would like to see further research into the treatment of delirium as well as its prevention.
‘We often apply the same principles of care to treatment as to prevention, but the effectiveness of this is not quite clear,’ she added.