Sudden confusion in the hospital may signal higher dementia risk later in life
· Medical Xpressby Sanjukta Mondal, Medical Xpress
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Hospitalized older adults can suddenly become disoriented and struggle to make sense of their surroundings. This condition, known as delirium, disrupts attention, awareness and clear thinking. The confusion can set in abruptly or come and go, sometimes changing in severity over time. It is far from rare, as it affects up to 30% of older hospital patients and as many as 80% of those in intensive care units (ICUs). There are several factors that can trigger such a state, including an infection, surgery or even certain medications.
A recent study set out to explore if delirium during hospitalization could have lasting consequences for memory and thinking. The researchers followed 3,501 older adults enrolled in the Mayo Clinic Study of Aging (MCSA), all of whom had experienced at least one hospital stay between 2004 and 2023, but none had dementia before being hospitalized.
The team kept track of their cognitive health for a median of 7.2 years, putting participants through in-person memory and thinking tests every 15 months. Neurologists and neuropsychologists assessed whether they developed mild cognitive impairment (MCI) or dementia over this period.
According to results published in JAMA Neurology, the consequences of delirium appeared to extend far beyond the hospital walls. Older adults who experienced an episode during or shortly after hospitalization were more likely to face more severe cognitive impairment and faster cognitive decline. Their risk of developing dementia was 5.39 times that of patients who had not experienced delirium.
The lasting imprint
An episode of delirium is not just a temporary disturbance in mental functioning; it does have the potential to impact overall brain health in the long run. Studies have found that it could also increase the risk of dementia and speed up cognitive decline.
However, much of the earlier research had a significant gap. Researchers often had no objective record of how well a person's brain was functioning before delirium set in. Instead, they had to rely on patients recalling their earlier abilities, accounts from family members or caregivers, or information recorded in medical files. This made it difficult to establish how much their cognitive abilities had changed after delirium.
The researchers eliminated recall bias because participants in the MCSA program had been undergoing in-person clinical evaluations every 15 months, long before any of them were hospitalized. So when delirium occurred, the researchers could compare actual test scores from objective measurements of brain function prior to acute illness, without relying on someone's recollection or external medical records.
Analysis of data collected across repeated 15-month follow-ups, spanning 4.1 years for some participants and more than a decade for others, showed that patients who experienced delirium had 3.67 times the risk of developing MCI, an early stage of noticeable memory and thinking difficulties. Memory and thinking test scores dropped much more rapidly over time in patients with delirium.
For example, test scores changed by an average of −2.28 points in those with delirium, compared with −0.43 points in those without, over five years. They also found that delirium remained a strong predictor of cognitive decline, independent of genetics and demographics.
The researchers suggest delirium be treated as a medical emergency due to its lasting effects on the cognitive health of older adults. Doctors' attention to delirium, from preventing episodes to catching them early to tracking patients' recovery after discharge and alerting families about the risks, can make a difference to patients' long-term brain health.
Written for you by our author Sanjukta Mondal, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.
Publication details
Allyson K. Palmer et al., Delirium and Long-Term Cognitive Trajectories in Cognitively Unimpaired Adults, JAMA Neurology (2026). DOI: 10.1001/jamaneurol.2026.4001
Journal information: Archives of Neurology
Key medical concepts
DeliriumDementiaCognitive DeclinesMild Cognitive Impairment
Clinical categories
NeurologyHealthy agingGeriatric palliative carePsychology & Mental health Who's behind this story?
Sanjukta Mondal
Master's in Chemistry. Freelance science journalist and communicator. Published in Chemistry World, BioSpace, and The Hindu. Full profile →
Sadie Harley
BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries. Full profile →
Robert Egan
Bachelor's in mathematical biology, Master's in creative writing. Well-traveled with unique perspectives on science and language. Full profile →
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