In Dementia, Infections Significantly Raise Mortality Risk


Short-term and long-term mortality are significantly higher among people with dementia who acquire infections, according to new findings presented at the Alzheimer’s Association International Conference.

These findings emerged from a nationwide registry-based prospective cohort study (N = 1,496,436 over 12,739,135 person-years). Data were obtained from Danish national registries, and follow-up occurred from January 1, 2000 or the participants’ 65th birthday (whichever occurred later) until death, immigration, or December 31, 2015.

The researchers defined the primary exposure as incident dementia and a first infection after the beginning of follow-up, and defined the primary outcome as all-cause mortality. They calculated mortality rate ratios (MRR) for the following exposure groups, which were stratified by sex and infection site categories:

  • Dementia/Infection (infection before or after dementia)
  • Dementia/No Infection
  • No Dementia/Infection (reference group)

The researchers also calculated MRRs based on time since first infection and according to infection site.

Results of the study indicated that 575,260 patients died over the course of follow-up, of whom 82,573 had dementia. The MRR for the Dementia/Infection group was 6.52 times higher than that of the reference group, and was also found to be higher in men. Among patients with dementia, MRRs were significantly higher among those with infections in all site categories compared with patients without dementia. The highest and lowest ratios were observed for sepsis and ear infections, respectively.

Notably, MRRs were found to be highest during the first 30 days following onset of the first infection among patients with dementia, and MRRs for patients with dementia remained higher than those for patients without dementia until 10 years after the first infection. The researchers noted that similar trends occurred in all of the infection site categories that were assessed.

“Our findings identify people with dementia and infections as a vulnerable group who need clinical attention,” the researchers concluded.

—Christina Vogt

Janbek J. Increased excess short- and long-term mortality following infections in dementia: A prospective nationwide and registry-based cohort study. Paper presented at: Alzheimer’s Association International Conference; July 27-31, 2020; Virtual.