A new study published in the latest edition of the British Medical Journal shows that patients who had at least one episode of delirium while in hospital went on to develop dementia at triple the rate of patients who had not experienced delirium.
Delirium is a sudden change in a person's mental state and is characterised by disorientation and confusion. It is common in older people during hospitalisation. Previous research has shown it affects more than 40 per cent of people aged 80 and older.
The new retrospective study is a collaboration between researchers from the University of Queensland (UQ) and the Australian Institute of Health Innovation (AIHI) at Macquarie University.
To reach these findings, the research team examined an immense dataset containing millions of public and private hospital records for patients aged 65 and older between 2001 and 2020, before narrowing the date range.
From this, patients were identified who had experienced at least one episode of delirium during hospitalisation. Each was paired with a ‘twin’ who shared characteristics such as age and sex but who had not experienced delirium, giving researchers 55,211 pairs to follow over five years.
These results don’t prove categorically that delirium leads to dementia, but we have found a strong causal relationship between the two, which is a very large smoking gun, you might say.
The delirium cohort was diagnosed with dementia at three times the rate of the non‑delirium cohort, with each additional episode of delirium associated with a 20 per cent increase in the risk of dementia.
In addition to this, the delirium cohort were 39 per cent more likely to die in the period under review.
Clusters revealed
The work arose from a study on frailty being run by the NHMRC Partnership Centre for Health System Sustainability led by AIHI Founding Director, Professor Jeffrey Braithwaite.
Rather than being an inevitable part of aging, frailty has been identified as a medical condition resulting in poorer physical and cognitive reserves and a poorer quality of life.
AIHI Professor of Medical AI, Shlomo Berkovsky, led the Macquarie University team who analysed the enormous dataset.
Huge dataset: Professor Shlomo Berkovsky analysed anonymised hospital records from 110,000 people aged over 65 to find a link between delirium and dementia.
“We requested this information from NSW Health to look at the causes of frailty in elderly people,” Professor Berkovsky says.
“All elderly patients who are admitted to hospital are assessed for frailty and receive a frailty score. This indicates whether they can safely undergo treatments such as heart surgery, but it doesn’t specify exactly what aspect of their health is contributing to their poor physical condition.
"As we analysed the data, we could see different clusters appearing, including dementia. University of Queensland clinician researchers were already looking at potential links between delirium and dementia, and they were able to develop the critical question we needed to direct our analysis.
“These results don’t prove categorically that delirium leads to dementia, but we have found a strong causal relationship between the two, which is a very large smoking gun, you might say."
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Dr Emily Gordon, UQ Centre for Health Systems Research Fellow, and the paper’s lead author, says the findings of the study have major implications for clinical practice.
“We know that delirium is common and dangerous,” she says.
"We also know about 40 per cent of delirium cases are preventable, with readily available interventions such as keeping hydrated, well nourished and mobile.
"So it follows that delirium prevention and treatment are likely to be unrivalled opportunities to reduce the burden of dementia globally."
Shlomo Berkovsky is a Professor of Medical AI at the Australian Institute of Health Innovation, the Macquarie University Lifespan Health and Wellbeing Research Centre and Macquarie University Data Research Centre.
