Infection Ups Mortality Risk in Patients With Dementia

Megan Brooks

July 27, 2020

Infection increases mortality risk among patients with dementia, new research suggests.

A large, registry-based cohort study showed that those with dementia had a greater than sixfold increased risk of dying after acquiring any infection than those without dementia or an infection.

"This is the first study to our knowledge to show that increased mortality is observed across all infection types in people with dementia and that increased mortality is seen both short and long term," coinvestigator Janet Janbek, PhD student, Danish Dementia Research Center, Rigshospitalet, University of Copenhagen, Denmark, told Medscape Medical News.

The findings were presented at the Alzheimer's Association International Conference (AAIC) 2020, which was held online this year because of the COVID-19 pandemic.

Large Danish Cohort

The investigators analyzed data from Danish national health registries for nearly 1.5 million individuals aged 65 and older who had visited the hospital with an infection. There were 575,260 deaths during more than 12.7 million person-years of follow-up.

Patients with dementia who also had a hospital visit for infection died at a 6.5 times higher rate than participants without dementia or an infection. Those with either dementia alone or infection-related contacts alone had a threefold increased rate of death.

Table. Mortality With Any Infection

Exposure groups Mortality rate ratio (95% CI)
Dementia + infection 6.52 (6.43 – 6.60)
Dementia/no infection 3.12 (3.08 – 3.16)
No dementia/infection 3.19 (3.17 – 3.21)
No dementia/no infection 1 (reference)


The mortality rate was highest within the first 30 days following the hospital visit for infection. However, the rate remained elevated for 10 years after the initial infection-related hospital visit.

Mortality rates from all infections, including major infections, such as sepsis, down to minor ear infections were elevated in patients with dementia compared with people who did not have dementia or an infection-related hospital visit.

Janbek said there are several possible explanations for the association of infection and increased mortality risk in those with dementia.

"After a hospital contact with a severe infection, people with dementia may become more reliant on external care, become more frail, and have declined functional levels, which might explain the observed association," she said.

It might also be that patients with dementia have more severe infections than those without dementia at the time of hospital contact, possibly because of delayed diagnosis, which could explain the higher mortality rates, said Janbek.

"It is also plausible that infections play a role in worsening dementia and subsequently lead to increased mortality," she noted.

"Clinicians and healthcare personnel need to pay closer attention to infections of all types in people with dementia, and steps towards better clinical management and improved post-hospital care need to be explored and undertaken. We need to identify possible preventive measures and targeted interventions in people with dementia and infections," Janbek said.

"Interesting Observation"

Commenting on the study for Medscape Medical News, Rebecca M. Edelmayer, PhD, director of scientific engagement for the Alzheimer's Association, said it presents "an interesting observation."

However, "we can't make any direct assumptions from this research per se about infections and dementia and whether they're causative in any way," noted Edelmayer, who was not involved with the study.

Instead, the study highlights the importance of "taking care of our overall health and making sure that individuals that might be vulnerable to infection, like those who are already living with dementia, are getting the best care possible," she said.

Janbek and Edelmayer have reported no relevant financial relationships.

Alzheimer's Association International Conference (AAIC) 2020: Poster 38941, presented July 27, 2020.

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