Hospital delirium linked to higher later dementia risk in a long-running Mayo aging study

What the study did

The Mayo Clinic Study of Aging is a population-based study of cognitive aging among residents of Olmsted County, Minnesota, with expert cognitive evaluations about every 15 months. Researchers looked at 3,501 participants without dementia who were hospitalized at least once between 2004 and 2023. Their median age was 74.1 years and about 48% were women.

Delirium, a sudden state of confusion with poor attention, was identified from hospital and follow-up clinical notes using a validated natural language processing tool. The team then compared later rates of mild cognitive impairment (MCI) and dementia, adjusting for age, sex, education and APOE e4 status, the best-known genetic risk factor for Alzheimer’s disease.

What it found

Over a median of 7.2 years, 75 participants (2.1%) had documented delirium within 30 days of a hospital stay. Delirium was associated with a higher risk of MCI (adjusted hazard ratio 3.67, 95% CI 2.19 to 6.15) and dementia (adjusted hazard ratio 5.39, 95% CI 2.94 to 9.85). People who had delirium also declined faster on repeated cognitive testing, including those whose thinking was normal before the hospital stay.

What it does not prove

This is an observational study, so it shows an association, not cause and effect. Delirium may be an early sign of brain vulnerability that was already present, rather than a cause of later decline. Only 75 people had delirium, so the estimates are imprecise, and an algorithm reading clinical notes will miss some cases. The population was largely from one Minnesota county, which may limit how well the results apply elsewhere.

The study also cannot tell us whether preventing delirium would lower dementia risk. That question needs intervention trials, which are still limited.

The Youthful take

Protecting the brain is central to living youthful, and hospital stays are a vulnerable moment. Many hospitals already use simple, non-drug measures to lower delirium risk, such as keeping glasses and hearing aids in use, supporting sleep, staying mobile, staying hydrated and reviewing medications with the care team. Families of older adults can ask about these steps before a planned surgery or admission.