A Study Of 53,000 People Found This Surprising Link To Dementia Risk

Dementia affects millions of people worldwide, yet there are still no treatments that can stop or reverse the disease. That's why researchers continue to search for lifestyle and health factors that may lower risk—and new research points to one that often flies under the radar: severe bloodstream infections.

In a large study of more than 53,000 adults in Wales, people who experienced a bloodstream infection were significantly more likely to develop dementia over the following decade than similar adults who never had one.

While the findings don't prove infections cause dementia, they add to growing evidence that severe infections (and the inflammation they trigger) may have lasting effects on brain health.

About the study

Researchers in Wales drew from a population of 2.5 million people to identify 26,792 individuals who had a confirmed bloodstream infection and matched them 1:1 to people who hadn't.

Bloodstream infections (where bacteria enter the bloodstream directly) are already known to cause acute cognitive effects like delirium, but their long-term impact on brain health has been less studied. Both groups were followed for up to 10 years to see who went on to develop dementia.

People who had a bloodstream infection developed dementia at a significantly higher rate

Compared to matched controls, people who experienced a bloodstream infection had a substantially higher risk of developing dementia over the next decade.

Ten years after infection, bloodstream infections were associated with approximately 160 additional dementia cases per 1,000 people compared to those without an infection. The same increase wasn't seen among people hospitalized for knee replacement surgery, suggesting the elevated risk wasn't simply due to being hospitalized or having a major medical event.

Researchers did observe a small increase in lung cancer risk after bloodstream infections, indicating some residual confounding may still exist. However, that increase was much smaller than the dementia association, suggesting it likely doesn't fully explain the findings.

Why might severe infections affect the brain?

This study shouldn't cause alarm—bloodstream infections are relatively uncommon, and most people who experience one won't necessarily develop dementia.

Instead, the findings reinforce an important message: protecting your overall health may also protect your brain.

Preventing infections through everyday habits like staying up to date on recommended vaccines, practicing good hand hygiene, promptly treating infections, and managing chronic conditions may have benefits that extend beyond short-term health.

Researchers say future studies should investigate whether preventing or aggressively treating severe infections could become another strategy for reducing dementia risk.

The takeaway

This study is observational, meaning it shows a connection rather than direct cause and effect. But the signal is strong, the mechanism is plausible, and the research is building. Bloodstream infections, it turns out, may be one of the more overlooked factors in long-term dementia risk, and that's worth knowing.