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Cognitive skills decrease with history of severe infections

A history of severe infections may be associated with impaired general cognitive ability, according to recently published data.

“Infections have previously been associated with both depression and schizophrenia, and [they have] also been proven to affect the cognitive ability of patients suffering from dementia,” Michael Eriksen Benrós, MD, PhD, of the mental health center at the University of Copenhagen, Denmark, said in a press release. “This is the first major study to suggest that infections can also affect the brain and the cognitive ability in healthy individuals.”

Benrós and colleagues examined the cognitive ability test data of 161,696 adult men available through multiple Danish national registries. Participants were born in Denmark from 1976 to 1994 and had information regarding infection-related hospital contacts, psychiatric disorders, parental education and intelligence available. Cognitive ability was measured using the Børge Prien’s Prøve Danish intelligence test administered from 2006 to 2012, but converted to parallel conventional IQ scaling for analysis (mean = 100, standard deviation = 15).

The mean age of included men was 19.4 years, and 34.79% had records of prior hospital contact with infection. Scores from this population were on average 1.76 units lower (95% CI, –1.61 to –1.92) than those with no recorded hospital contacts for infection.

This reduction increased if infection was more recent (P < .001) and if it required more days hospitalized (P < .001). Further decreases also were observed among those with frequent or diverse infection histories, and they were greatest among those with 10 or more hospital contacts for infection (mean = –5.54; 95% CI, –3.89 to –7.2) or those hospitalized for five or more different types of infection (mean = –9.44; 95% CI, –5.69 to –13.2).

“The study thus shows a clear dose-response relationship between the number of infections, and the effect on cognitive ability increased with the temporal proximity of the last infection and with the severity of the infection,” Benrós said in the release. “Therefore, it is important that more research is conducted into the mechanisms which lie behind the connection between a person’s immune system and mental health.” – by Dave Muoio

Disclosure: The researchers report no relevant financial disclosures.