Are hospitalizations with infection associated with dementia incidence?

By Dr. Sanchari Sinha Dutta, Ph.D.Jan 10 2023Reviewed by Danielle Ellis, B.Sc.

A recent study published in JAMA Network Open suggests that hospitalized patients with infection are at higher risk of developing dementia.

Background

Dementia is a group of conditions related to impaired memory, thinking, and social abilities. According to recent estimates, about 50 million people are affected by dementia worldwide. The number of affected people has been predicted to be 152 million by 2050.

Alzheimer’s disease is the most common form of dementia. Studies involving Alzheimer’s disease patients have identified neuroinflammation as a potential causative factor for dementia. Hyperactivation of brain immune cells is responsible for neuroinflammation. Recent evidence suggests that systemic inflammation caused by peripheral infection might also be associated with neuroinflammation.

In the current study, scientists have evaluated whether hospitalization with infection increases the risk of incident dementia.

Study design

The current study data was obtained from a US-based study on atherosclerosis risk in communities over more than 32 years. The current study included a follow-up period of 2017 to 2019.

A total of 15,688 participants who did not have dementia at baseline were included in the analysis. Medical records of the participants were reviewed to identify hospitalization with infection.

Dementia cases occurring less than three years or more than 20 years after hospitalization with infection were excluded for the sensitive analysis to remove cases that might not be directly related to any infection events.

Important observations

During the follow-up period of 32 years, dementia was diagnosed in 19% of participants, giving rise to an incidence rate of 8.2 events per 1000 person-years. Older participants, female participants, members of the Black ethnic group, or APOE-ε4 (genetic risk factor for Alzheimer’s disease) carriers were found to be more susceptible to develop dementia.

Considering various vascular parameters at baseline, high blood pressure and previous incidence of stroke or transient ischemic attack were identified as risk factors for dementia.

About 38% of participants were identified to have a hospitalization with infection. The most common infections were respiratory tract (19%) and urinary tract (12%) infections.

Association between infection exposure and risk of dementia

The incidence rate of dementia among participants with infection exposure was estimated to be 23.6 events per 1000 person-years. In contrast, unexposed participants had a dementia rate of 5.7 events per 1000 person-years.

Specifically, participants with hospitalization with infection had almost 2-fold higher risk of developing dementia. The sensitive analysis findings revealed that participants exposed to infection had almost 6-fold higher risk of incident dementia.

The comparison between the type of infection and risk of dementia revealed that participants with respiratory, urinary tract, skin, blood, circulatory or hospital-acquired infection had a higher risk of incident dementia.

Further statistical analysis identified blood and circulatory system, urinary tract, and hospital-acquired infections as the highest risk factors for incident dementia. The findings of subgroup analysis revealed a significant association between hospitalization with infection and the risk of dementia.

Furthermore, hospitalization with infection was found to associate with older age, current or former smoking, lower education, APOE-ε4 noncarrier status, and several vascular factors.

Study significance

This large-scale observational study suggests that individuals with any hospitalization with infection have approximately 70% higher risk of developing dementia. The risk is highest among individuals with blood and circulatory, urinary, or hospital-acquired infection.

Infections increase the risk of vascular and metabolic diseases, including coronary heart disease, heart failure, stroke, and diabetes. These diseases are known risk factors for dementia.

As mentioned by the scientists, further studies are required to establish the link between infection and dementia. Future studies should evaluate the impact of hospitalization without infection, frailty, or comorbidities on dementia risk. Moreover, the relationship between infections and known biomarkers of dementia should be investigated.