Severe infections may have long-lasting effects, causing long-term brain damage and reduced IQ, according to new research. (Photo: Colourbox)

Infections can damage your intelligence

Serious infections damage your cognitive abilities and can lead to fatigue, headaches, and stress.

Severe infections may have lasting effects and can cause long-term brain damage. No matter where in the body it attacks, an infection could even impair intelligence, shows new research.

"We’ve examined whether intelligence is affected by serious infections that resulted in hospitalisation. We’ve seen that there is an effect, and that it's not limited to infections in the brain—infections elsewhere in the body can impair cognitive abilities," says Ph.D. Michael Eriksen Benrós, MD, from the Psychiatric Centre in Copenhagen.

Benrós is one of the researchers behind a new study which demonstrates that people, who at some stage in their life have been hospitalised with an infectious disease, on average have a lower IQ than their peers. The study was recently published in PLOS One.

Neuropsychologists should monitor patient recovery

The study's results should have consequences, says Peter Leutscher, head of research at the Regional Hospital of Randers, Denmark.

According to Leutscher, the study results suggest introducing a new approach in hospitals, where neuropsychologists are present on the wards treating serious infections.

"This study clearly shows that the brain can be subjected to long-term damage from an infection. It must be taken seriously and [we should] begin to follow up on the patients’ cognitive development after they have been discharged from the hospital," says Leutscher. He was not involved with the new study.

"Hospitals in the USA already have neuropsychologists affiliated with infection departments. We should consider doing the same in Denmark, "he says.

Severe infections lead to lower IQ

In the new study, Benrós and colleagues examined registry data for 190,000 young Danes born between 1976 and 1994 who had their IQ measured when they entered the enlistment process for military service.

Around 35 per cent of these young people had been hospitalised with one or more infections before enlisting and their IQ was on average lower than those who had not suffered such an infection.

The researchers found that serious infections throughout the whole body are associated with lower IQ, though infections in the brain are particularly harmful.

IQ was particularly lower in those who had suffered multiple infections and in those who had been infected most recently—indicating that the brain eventually heals, and that intelligence improves over time.

Other brain-related complications

This is the first direct evidence that IQ is affected by infections. Although researchers have known for some time that severe infections, especially in the brain, are associated with memory problems, headaches, fatigue, and stress long after patients have recovered and are discharged from hospital.

Leutscher has previously published a study which shows that meningitis patients suffer from brain-related problems even after they are declared healthy.

"A neuropsychologist followed the patient’s recovery for twelve months after they’d been hospitalised with meningitis. The follow-up showed that the patients were tired, had headaches, and had trouble when surrounded by too many people. They found it difficult to return to work and many suffered from stress," says Leutscher.

Infection triggers a harmful cytokine storm

Scientists are not sure how intelligence is damaged by severe infections but they suggest that infections may trigger a violent immune response, a so-called cytokine storm.

When infection strikes, the body sends messenger proteins called cytokines into the blood. Cytokines ensure that the immune system is activated to fight infections but they can also damage the body's cells.

"If the infection is severe and difficult to deal with the immune system goes into high alert. It’s likely that a cytokine storm can become so violent that the cytokines are carried with the blood and penetrate the brain barrier even though the infection is occurring somewhere else in the body, "said Leutscher.


Read the original story in Danish on

Translated by: Catherine Jex

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