A fascinating study tracking thousands of people for 20 years has revealed an intriguing association between signs of chronic inflammation in middle age, and the development of memory and thinking problems in older age. Alongside offering an important new risk factor for cognitive decline later in life, the research suggests treating chronic inflammation at a younger age may act as a preventative measure for future neurodegeneration.

A growing body of research is beginning to suggest interesting correlations between autoimmune diseases and psychological conditions. The hypothesis is that long-term inflammation can influence the neurodegeneration that results in everything from Alzheimer's to suicidal thoughts.

"Chronic inflammation is tough on the body, and can damage joints, internal organs, tissue and cells," explains Keenan A. Walker, one of the authors on the new research. "While other studies have looked at chronic inflammation and its effects on the brain in older people, our large study investigated chronic inflammation beginning in middle age and showed that it may contribute to cognitive decline in the decades leading up to old age."

So, to better understand the relationship between chronic inflammation and its potential long-term effects on the brain, the study tracked over 12,000 subjects for 20 years. At the beginning of the study the subjects reported an average age of 57, and blood samples analyzed the levels of four known inflammatory biomarkers. Thinking and memory skills were tested at three points in the study: at the beginning, six to nine years in, and at the end.

The ultimate results were small but statistically significant. Those with the highest level of inflammatory biomarkers at the beginning of the study revealed an 8 percent greater decline in cognitive skills over the 20-year period, compared to those with low inflammatory biomarkers. Higher levels of one inflammatory marker in particular, C-reactive protein, represented even higher degrees of cognitive decline, with those displaying the highest levels of this biomarker at the start of the study displaying a 12 percent greater decline in cognitive measurements.

"Our results show that chronic inflammation may be an important target for intervention," says Walker. "However, it's also possible that chronic inflammation is not a cause and instead a marker of, or even a response to, neurodegenerative brain diseases that can lead to cognitive decline."

It is important, as Walker notes, to point out this study makes no causal conclusion between inflammation and cognitive decline. Further research will certainly home in on this relationship, looking more specifically into specific inflammatory markers and how they could be resulting in longer-term neurodegeneration.

The new research was published in the journal Neurology.