Cognitively normal older adults with elevated levels of chronic inflammation during middle age experienced an 8 percent steeper decline in cognitive ability compared to those who had the lowest levels of inflammation. These are the findings of a prospective study published online in Neurology on February 13.

Pros and Cons of Inflammation

Inflammation occurs in response to an infection or injury to prevent tissue damage. When it becomes chronic, persisting for months and years, due to an autoimmune disorder such as rheumatoid arthritis or lupus, and other conditions such as heart disease and stroke, it can cause damage.

Researchers at Johns Hopkins University in Baltimore analyzed blood samples drawn from 12,336 participants in the Atherosclerosis Risk in Communities (ARIC) study, an ongoing, population-based prospective study that investigates the causes of atherosclerosis—the hardening and narrowing of the arteries caused by plaque buildup. The average age was 57 years at baseline and 76 years at the final assessment. Of the sample size, 56 percent were women and 21 percent were black.

The team conducted in-person evaluations over five visits and assessed cognition, including memory, executive function, and language in three visits over 20 years.

On the first two visits, the researchers collected blood samples to assess inflammatory biomarkers. They measured four blood biomarkers, including three proteins involved in blood clotting and white blood cell counts to develop an “inflammation composite score” on the first visit. On the second visit, they looked at C-reactive protein levels—a measure of inflammation.

During the analysis, the team accounted for age, education, blood pressure, cholesterol, heart disease and a range of factors that may influence cognition.

Inflammation Is Tied to Poor Thinking Skills

Participants with the highest inflammation composite score had an 8.9 percent steeper decline in cognitive ability than those with lower composite scores. Similarly, participants who had the highest C-reactive protein levels had a 12.3 percent steeper decline in mental ability.

Participants with higher levels of inflammatory markers were predominately older, female, and black, and had elevated rates of cardiovascular risk factors and lower cognition at baseline.

Important Link

The researchers suggested that chronic inflammation could be a marker or a response to neurodegenerative brain diseases that may lead to cognitive decline.