HEALTH NEWS

Study Title:

Inflammation, Intelligence, and Premature Death

Study Abstract

Objective
To investigate if signs of inflammation are associated with performance on a contemporaneous IQ-test in males aged 18–20.

Design
Cohort study using data from the conscript register on performance on an IQ-test and on erythrocyte sedimentation rates (ESR) measured in 1969/70. Data on cardiovascular risk factors measured at conscription and national register data on childhood circumstances at age 10 were considered as potential sources of confounding. Data from national registers was linked to the cohort in order to explore long term associations between ESR at age 18–20 and mortality between the years 1971–2006.

Setting
49,321 Swedish males aged 18–20, screened for general health and for mental and physical capacity at compulsory conscription examination before military service.

Results
We found an inverse correlation between ESR and performance on an IQ-test. While an association was observed across IQ bands and ESR ranges, independent of cardiovascular risk factors or childhood circumstances, the association was slightly attenuated by adjustment for childhood socioeconomic position (SEP). An association between childhood SEP and ESR was detected that remained after adjusting for IQ. The ESR was also associated with future mortality following adjustment for childhood SEP.

Conclusions
Low-grade inflammation, as indicated by the ESR, is associated with reduced cognitive abilities already at age 18–20.

From press release:

Inflammation is associated with lower intelligence and premature death, according to Swedish scientists from the Karolinska Institute in Stockholm, Sweden. "Those with low-grade inflammation performed more poorly on standardised intelligence tests, even after excluding those with signs of current illness. Inflammation also predicted an increased risk of premature death," said lead researcher Dr Hakan Karlsson.

The research, recently published in Brain, Behavior and Immunity, used large population-based registers containing data collected over several decades. Inflammation and intelligence were measured at 18-20 years of age in nearly 50,000 young men, and deaths over the following 35 years were recorded.

"Although we knew that inflammation associated with infection or cardiovascular disease could impair brain function, this is the first time that similar associations have been shown in healthy young people," said Dr Karlsson. "This suggests that even low levels of inflammation can have detrimental consequences for health and brain function," he added.

"Since low-grade inflammation appears to be hazardous, it is also important to determine its causes," affirmed Dr Karlsson. "One interesting possibility is the role of environmental factors during childhood," he added. In the current study, childhood socio-economic status predicted the level of inflammation seen in young adulthood. For example, children of farmers had higher levels of inflammation than those whose fathers were non-manual workers. "It's possible that these boys were exposed to more toxins, allergens or infectious agents in childhood, leading to greater inflammation and its negative effects later in life," he remarked.

"This is an important finding because it is the largest study to date to show that low-grade inflammation in young adulthood is associated with intelligence and mortality," said Dr Michelle Luciano, from the Centre for Cognitive Ageing and Cognitive Epidemiology at the University of Edinburgh. "An interesting question now is whether the effects of a less healthy childhood environment on inflammation persist into middle age and beyond," she commented

Study Information

1.Håkan Karlsson, Björn Ahlborg, Christina Dalman, Tomas Hemmingsson.
Association between erythrocyte sedimentation rate and IQ in Swedish males aged 18–20
Brain Behavior and Immunity
2010 August
Karolinska Institute in Stockholm, Sweden.