New research indicates that severe infections, such as cystitis, pneumonia, and dental issues, could elevate dementia risk. A comprehensive study in Finland involving hundreds of thousands of participants revealed that hospitalizations for these infections were linked to a higher probability of developing dementia, including early-onset dementia, within six years.

Current findings suggest that dementia, particularly Alzheimer’s disease, may be preventable or delayed through brain-training activities, lifestyle changes, and even sauna use. Further evidence now supports that minimizing infections may significantly lower dementia risk. “This indicates that the risk of dementia may be partially modifiable,” says Quantin Wu from Emory University in Atlanta, Georgia, who was not part of the study.

In 2021, researchers including Piry Sipila from the University of Helsinki observed that hospitalized individuals with severe infections exhibited higher rates of dementia. However, it remains unclear if this correlation arises from underlying conditions like diabetes, which can heighten vulnerability to both dementia and infections. Dementia and infections susceptibility are critical topics of discussion.

To explore this further, researchers analyzed health records from 62,555 individuals aged 65 and older, all of whom were free from dementia in 2016 but diagnosed between 2017 and 2020. This cohort was compared with 312,772 dementia-free individuals matched by age, gender, education, and marital status, highlighting a two-decade span of diagnoses and hospitalization records.

The team identified 29 symptoms linked to an approximately 20% increased risk of developing dementia within the following five to six years. Notably, while most symptoms were non-infectious and concerned other health issues, cystitis and nonspecific bacterial infections specifically contributed to heightened dementia risk. Subsequent evaluations indicated that infections primarily drove this increase compared to 27 other health conditions.

While inflammation is a crucial immune response to infections, it also plays a role in certain dementia types, including Alzheimer’s disease. Infection-induced inflammation can damage the brain’s circulatory system, leading to microbleeds and the infiltration of toxins through the blood-brain barrier, according to Shipira. Moreover, there is increasing evidence that vaccines targeting infections like shingles and influenza may lower dementia risk.

In another segment of the research, a focus was placed on early-onset dementia, identified in individuals under 65. Although conditions such as Parkinson’s disease and head trauma pose significant risks, multiple infections—including gastroenteritis, colitis, pneumonia, and dental infections—were found to have associations with early-onset dementia.

The variation in which specific infections affect either early-onset or standard-onset dementia remains unclear. The researchers noted differing causes and genetic susceptibilities associated with these dementia types in their findings.

Despite the robust correlations observed, it’s uncertain if these infections are direct causative agents of dementia or if mere correlations arise from confounding variables. “To clarify, intervention trials are essential to assess whether improved infection prevention can effectively lower or delay dementia onset,” Cipila asserts.

“Gil Livingston,” a professor at University College London, expressed openness to the possibility that such studies may affirm causal links. “This high-quality research aligns with other evidence, and when considering the timeline and biological plausibility, it seems likely,” she states.

This insight could significantly enhance strategies for preventing, managing, and monitoring serious infectious diseases, according to Wu. For instance, preventing cystitis involves maintaining adequate hydration and administering appropriate incontinence care. “Timely treatment is vital as UTIs in older adults often manifest unusually, such as through confusion or delirium, which can lead to missed or delayed diagnoses,” she emphasizes. “This study is both concerning and motivating.”