By Daniel Davis
Taking an elderly friend or relative to hospital is a painful experience for most people, and is often made worse when they become confused and disorientated during their stay.
This acute confusional state is called delirium. Long thought to be thought to be little more than a temporary side effect of other illness, ground-breaking new research suggests that delirium in fact has long-lasting negative impacts on the brain.
Delirium is extremely common, affecting around 120 people in a typical 1000-bedded hospital. People with delirium can lose their bearings, forgetting where they are. They may even become very distressed because they imagine that hospital staff or even visiting relatives are part of a conspiracy to harm them. Delirium is also associated with an increased risk of new and permanent admission to a nursing home, and death. But less than a quarter of cases are formally detected in hospitals.
Delirium is the result of illness – often an infection, a reaction to medications, or an operation – but it has generally been assumed that it is short-lived and benign. This assumption is wrong. Though delirium usually ends when the underlying causes are treated, this new study suggests that it may in fact be associated with new damage to brain, accelerating the path to dementia.
The personal and societal costs of dementia are enormous. In the UK, we spend 23bn annually across health and social care – already more than expenditure on cancer and heart disease combined. There are no proven methods of preventing dementia, and treatments are only modestly effective. So any knowledge of methods of reducing the risk of dementia is extremely valuable. This study implies that delirium prevention might actually prevent or delay the onset of dementia. Importantly, delirium prevention has been well-studied, and has been shown to work.
This study from the University of Cambridge and the University of Eastern Finland investigated how delirium affected the risk of future dementia in a study of persons aged 85 and older; the study was named Vantaa85+ after the city where it was carried out.
Cognition was assessed at regular intervals over 10 years, before and after episodes of delirium. This was a major advantage, because other studies of hospital patients were unable to establish a person’s cognitive function prior to delirium and therefore be confident that the delirium was indeed associated with new changes.
Vantaa85+ reliably determined that delirium was associated with worse cognition in every way: increased risk of dementia, worsening severity if already diagnosed with dementia, and faster trajectory of cognitive decline. Delirium was also associated with greater levels of physical dependence following an episode.
The study is remarkable for specifically involving persons aged 85 and older because very old individuals are hardly ever represented in research on ageing and dementia. Another strength was that everyone of this age in the town was recruited – even if they were in institutional care, or already had dementia – so the results are generalisable to the wider population of older persons. Exceptionally, over half the participants agreed to donate their brains for autopsy. There is a continuing gratitude to the brain donors and their families for the scientific legacy they provided.
The findings from the autopsy studies were the first attempt to understand brain changes in relation to a population known to have had delirium. We know that dementia can result from a number of aberrant processes (e.g. deposition of abnormal proteins, blockages in blood vessels). However, when individuals had a history of delirium and dementia, these standard neuropathological markers were not enough to explain the dementia, raising the possibility that completely novel process led to dementia after delirium.
The work should spur on basic science research investigating the mechanisms underlying the relationship between delirium and long-term cognitive impairment.
Returning to the idea that delirium prevention may lead to dementia prevention, this should have a clinical impact on how delirium is managed in hospital. This should start with hospitals introducing formal programmes for delirium detection and prevention. On a personal note, family members should urge doctors responsible for their relatives’ care to be aware of, and try to control, delirium as a real threat to long-term health rather than a passing inconvenience.
Daniel H.J. Davis MB ChB is based at the Institute of Public Health, University of Cambridge. Brain: A Journal of Neurology has granted free access to the full paper on this topic, “Delirium is a strong risk factor for dementia in the oldest-old: a population-based cohort study“, which is co-authored by Daniel Davis.