Severe cystitis, pneumonia or tooth decay could increase the risk of dementia. A study of hundreds of thousands of people across Finland has found that people who were treated in hospital for these infections were significantly more likely to develop dementia – including an early-onset form of the condition – within the next six years. We increasingly think that dementia, including Alzheimer’s disease, could be prevented or delayed through brain-training games, steadfast lifestyle changes and even saunas. Now, the latest research adds to the mounting evidence supporting infection avoidance to further reduce the odds of developing the condition. “It suggests that dementia risk may be partially modifiable,” says Kuan-Ching Wu at Emory University in Atlanta, Georgia, who wasn’t involved in the study. In 2021, Pyry Sipilä at the University of Helsinki and his colleagues noticed that people who were hospitalised with severe infections were more likely to develop dementia. But it was unclear whether this was because they had other conditions like diabetes, which increases both the risk of dementia and infection susceptibility. To untangle …