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.
The research was funded by the Stanley Medical Research Institute, Bethesda, MD, USA, the Swedish Research Council, and the Swedish Council for Working Life and Social Research.