Predominantly perceived as something that subtly progresses over time, much like the unfurling of fog, dementia is often associated with advancing age, dictated by genetic and lifestyle factors, alongside existing health conditions like hypertension and diabetes. A new research study from Finland, however, suggests the likelihood of another contributing factor hidden away in hospital records — the link between severe infections and increased dementia risk.
This extensive Finnish study, published in PLoS Medicine in March 2026, delved into the health records of 62,555 individuals, aged 65 or older, suffering from ‘late-onset’ dementia, contrasting their medical history with 312,772 dementia-free control subjects. An intriguing trend surfaced, indicating that severe infections necessitating hospital treatment showcased a correlation with higher odds of developing dementia in later years.
In the pursuit of eliminating any confounding factors, the researchers analyzed data meticulously against prevalent medical conditions like Parkinson’s disease or alcohol abuse, and other chronic illnesses. Despite these adjustments, the connection between infections and dementia remained tangible, suggesting a potential linkage between diverse infections and cognitive dysfunction. On average, individuals who were treated for severe urinary tract infections were diagnosed with dementia around six years later, while other severe bacterial infections showed a pattern of occurring approximately five years before a dementia diagnosis.
Connecting such a long gap between an infection and the development of dementia is not conventional, but a related published article draws a connection between chickenpox caused by the varicella-zoster virus and later dementia development. This article also reveals how the shingles vaccine potentially reduces the risk of developing Alzheimer’s disease or vascular dementia, emphasizing the importance of preventive measures for dementia.
Persistent and severe inflammation, a common bodily response to infections, can inflict damage on delicate brain cells. Scientists have speculated for quite some time that neuroinflammation contributes to dementia and other infections, such as pneumonia, sepsis, and gum disease, are being studied for their potential links to cognitive decline. Even herpes simplex viral infections have been examined for their potential contribution to Alzheimer’s disease.
As part of the study findings, it was observed that individuals diagnosed with early-onset dementia (before age 65) displayed a stronger connection between infections and dementia risk. Complications from additional infections, including bacterial pneumonia, gastrointestinal infections, and dental decay, were linked to an increased risk of dementia.
Although the exact link between preventing infections early in life and protecting the brain from dementia in the future is unclear, it poses a compelling argument for further investigation. A prevalent belief among medical researchers dwells on the accumulation of amyloid plaque in the brain as the leading cause behind dementia. However, there is growing evidence indicating that amyloid may have strong anti-infective properties and its buildup might be the body’s mechanism of fighting off infections.
While the observations from the Finnish study cannot conclusively establish a cause-effect relationship between infections and dementia risk, it does open up the possibility that mitigating and promptly treating infections can play a pivotal role in dementia prevention. Although dementia is a complex disorder with no single cause or prevention strategy, the findings extend our understanding of its multifaceted nature and the potential role severe infections could play in its development.