People who suffer from high inflammation go on to experience more cognitive decline in later life, a study has found.
After following the same group of adults through middle age, researchers found that those with signs of chronic or increasing inflammation at the start of a study were more likely to perform poorly in tests of processing abilities 18 years later. The findings match similar work in older groups of adults.
Writing in the journal Neurology, the scientists who uncovered the link said this suggested that we should protect our cognitive health throughout life. “Inflammation is important for cognitive ageing and may begin much earlier than previously known,” the team, from University of California San Francisco, said. They added that the work underscored “the need to also target cognitive brain health in middle age”.
However, other scientists cautioned that the study, which involved more than 2,000 people aged 24 to 58, could not prove definitively that it was inflammation — a measure of immune activity — causing the decline in thinking skills. It may be instead, for instance, that illness or unhealthy habits lead to both cognitive effects and inflammation. They also said we would need a longer study to determine whether this then helped predict dementia risk.
Inflammation is associated with the body’s immune response. It rises in response to infection, but can also be kept at elevated levels through illness, stress, obesity, poor diet and lack of exercise. Persistent inflammation has been linked to a range of conditions, including heart disease and dementia, possibly due to cellular damage.
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The study found that those with high inflammation, or a trajectory of increasing inflammation, were about twice as likely to perform poorly on tests of processing speed and executive function, although not on other tests looking at, for instance, memory and verbal fluency. The results add to similar findings in other older cohorts that have also linked inflammation to declining brain function.
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In an editorial written alongside the paper Eleanor Conole, a neuroscientist at the University of Edinburgh, said that it makes the case for an earlier monitoring of inflammation. “As we age, we become less effective at resolving inflammation and are more prone to adopting a chronic, low-level inflammatory state. Understanding how early this process starts and how this relates to later-life cognition is key,” she said.
She added, though, that while it may be an indicator of a risk of cognitive decline, the precise nature of inflammation’s role in ageing was still to be properly worked out. “Understanding whether chronic inflammation is a cause, consequence or concomitant of evolving health status is key to elucidating its relationship with cognitive ageing.”
