Research shows that poor health and stress in your 20s takes its toll in your 40s with lower cognition

Higher inflammation in early life is associated with lower performance on skill testing in middle age. Young adults with higher levels of inflammation, which are linked to obesity, physical inactivity, chronic disease, stress and smoking, may experience decreased cognitive function in midlife, a new study from UC San Francisco shows.

Researchers previously linked higher inflammation in older adults to dementia, but this is one of the first studies to link inflammation in early adulthood to lower cognitive skills in middle age.

“We know from long-term studies that changes in the brain that lead to Alzheimer’s disease and other forms of dementia can take decades to develop,” said first author Amber Bahorik, Ph.D., of the UCSF Department of Psychiatry and Behavioral Sciences and the Weill Institute for Neuroscience. “We wanted to see whether health and lifestyle habits in early adulthood could play a role in cognitive skills in middle age, which in turn could influence the likelihood of dementia later in life.”

In their study published in Neurology on July 3, researchers found that only 10% of those with low inflammation performed poorly on tests of processing speed and memory, compared to 21% and 19%, respectively, of those with moderate or higher levels of inflammation.

When researchers adjusted for factors such as age, physical activity and total cholesterol, differences in processing speed remained; and the researchers also found differences in executive functioning, including working memory, problem solving and impulse control.

The study followed 2,364 adults in the CARDIA study, which aims to identify the factors in young adulthood that lead to cardiovascular disease two to three decades later.

Participants were 18 to 30 years old when they entered the study and were tested for the inflammatory marker C-reactive protein (CRP) four times over an 18-year period. They took the cognitive tests five years after their last CRP measurement, when most participants were between their forties and fifties.

About half of the participants were women; just under half were black and the rest were white. About 45% had lower stable inflammation, while 16% had moderate or increasing inflammation; 39% had higher levels.

A link between inflammation and health risks

The researchers also linked higher levels of inflammation to physical inactivity, higher BMI and current smoking.

“Inflammation plays an important role in cognitive aging and can begin as early as early adulthood,” says senior author Kristine Yaffe, MD, professor of psychiatry and behavioral sciences, neurology and epidemiology and biostatistics at UCSF. “There is likely a direct and indirect effect of inflammation on cognition.”

Yaffe is a member of the first team of experts to determine that 30% of the risk of dementia is preventable. Her recent research has looked at the link between midlife fragmented sleep and lower cognition and the effects of personalized health and lifestyle changes in preventing memory loss in higher-risk older adults.

“Fortunately, there are ways to reduce inflammation — such as by increasing physical activity and quitting smoking — that may be promising avenues for prevention,” Yaffe said.