Infections Tied to Increased Mortality in Dementia Patients

Post-infection mortality was higher in older adults with dementia than others in both the short- and long-term, an analysis of Danish national registry data showed.

Among 1.5 million adults followed for a total of nearly 13 million years, people who had both dementia and infection-related hospital visits died at a 6.5 times higher rate than people with neither (MRR 6.52, 95% CI 6.43-6.61) said Janet Janbek, MSc, of the Danish Dementia Research Centre, Rigshospitalet at the University of Copenhagen, and colleagues.

They also had a three-fold increased mortality rate over dementia-free older adults with infection-related hospital visits (MRR 3.19, 95% CI 3.17-3.21), they reported at the virtual Alzheimer's Association International Conference (AAIC).

The analysis builds on previous research that has linked pneumonia and sepsis to increased mortality in people with dementia, Janbek noted. A 2019 meta-analysis showed that risk of pneumonia-associated death in dementia patients was twice as high as among people without dementia. An observational study in Spain recently showed that sepsis was tied to higher in-hospital mortality in dementia patients than in their dementia-free counterparts. To date, no other infections or long-term mortality associated with infections overall have been investigated, the researchers said.

"Our nationwide study expands that knowledge and reports increased mortality in people with dementia across all types of infections," Janbek told MedPage Today. "We also report that increased mortality was both short and long-term -- 10 years after an infection -- which has not been shown before."

In their analysis, Janbek and colleagues looked at 1,496,436 people from Danish national registries who had been followed for a total of 12,739,135 person years, from January 2000 or the year they turned 65 (whichever came later) until death, immigration, or December 2015. A total of 575,260 people died during follow-up, including 82,573 individuals with dementia.

Primary exposure was incident dementia and first infection after start of follow-up. Incident dementia was determined by ICD codes or first redeemed anti-dementia drug. First infection was determined by ICD codes indicating first hospital contact with infection.

Mortality rate ratios in all infection sites were higher in the dementia group than in the no-dementia group. They were highest with sepsis and lowest with ear infections.

In the dementia group, MRRs were highest the first 30 days after onset of first infection. They remained higher than MRRs in the no-dementia group until after 10 years post-first infection.

"The study sheds light on the need for better clinical management and post-hospital care for people with dementia following infections," Janbek said. "It encourages research to further our understanding into which risk factors can explain the increased mortality following infections in people with dementia."

The study is limited by its observational nature. Comorbidities and unmeasured confounders may have influenced results.

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