Chronic inflammation in middle age may lead to memory and thinking problems later in life.

Unlike acute inflammation, which arises in response to injury, chronic inflammation persists over months or years. Autoimmune disease, lingering infection, exposure to polluted air, psychological stress and other conditions can all promote chronic inflammation.

Researchers conducted blood tests on 12,336 men and women with an average age of 57. They assigned participants an “inflammation composite score” based on white blood cell count, clotting factors and other tests.

They also assessed their cognition with standardized tests of memory, processing speed and verbal fluency. Participants were tested at the beginning of the study, six to nine years later, and at the end of the study, which was published in Neurology, the medical journal of the American Academy of Neurology.

After controlling for age, education, blood pressure, cholesterol, heart disease and other factors, they found that the greater the number of inflammatory factors, the steeper the cognitive decline over 20 years of follow-up. Inflammation was most strongly associated with declines in memory rather than other aspects of thinking such as language and executive functioning.

“Chronic inflammation is tough on the body, and can damage joints, internal organs, tissue and cells,” said study author Keenan A. Walker, a postdoctoral researcher at Johns Hopkins University in Baltimore, Md. “It can also lead to heart disease, stroke and cancer.”

He said other studies have concentrated on the effects of chronic inflammation on older people, but this 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.”

“We know that dementia starts earlier than the appearance of symptoms,” he said, “and we’ve shown that levels of inflammation matter for dementia risk.”

“Many of the processes that can lead to a decline in thinking and memory skills are believed to begin in middle age, and it is in middle age that they may also be most responsive to intervention,” he said.

Ways to reduce chronic inflammation include regular exercise, having a healthy diet, avoiding excessive weight gain and getting enough sleep.

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