Elevated Chronic Inflammation May Increase Dementia Risk
Older adults whose levels of chronic inflammation increased during midlife and were sustained through late-life showed visible structural damage in their brains. MRI scans revealed that those with elevated levels of a brain inflammation biomarker that remained high until later in life had similar brain structure damage to people 16 years older. These are the findings of an observational study published in the August issue of Neurobiology of Aging.
Systematic Inflammation and Structural Brain Changes
Structural brain changes are associated with normal aging. In older adults, abnormalities in white matter—the part of the brain responsible for transmitting messages—are common and unrelated to cognitive decline and dementia. Previous research has found an association between systematic inflammation and white matter abnormalities in the elderly, but it's unclear whether it’s due to chronic or sustained inflammation.
Current theories implicate co-existing health problems and systemic inflammation as potential drivers of neurodegenerative disease. Yet, studies that link inflammation to brain abnormalities have not observed the long-term effects of systemic inflammation among an elderly population.
Long-term Effects of Inflammation
To better understand how inflammation affects the brain and cognitive abilities over an extended period of time, a team of researchers from Johns Hopkins University in Baltimore gathered data on 1,532 participants from the Atherosclerosis Risk in Communities (ARIC) study, which assessed cardiovascular risk factors among middle-aged and older people.
The researchers looked at brain structure and integrity, and high-sensitivity C-reactive protein (CRP)—a marker in the liver of systematic inflammation—over a 21-year period, from middle age to late life. Sixty-one percent of participants were women and 28 percent were African-American. By the end of the study, participants were an average age of 76.
Measuring Inflammation
Through the duration of the study, each participant had five visits with ARIC researchers, about one every three years, on average. During visits two, four, and five, researchers drew blood samples to measure CRP levels; those below 3 milligrams per liter (mg/L) were considered low inflammation; 3 mg/L or higher was considered elevated.
On the last visit, each participant underwent an MRI brain scan to assess evidence of white matter damage.
Increasing CRP Levels Linked to White Matter Abnormalities
Participants whose inflammation levels increased from low to high during midlife had the most white matter damage, even after accounting for potentially modifying factors such as age, sex, levels of education, and risk of cardiovascular disease.
Elevating Inflammation Ages Brains
Using a program that measures structural integrity at the microscopic level, researchers estimated the brains of people with elevating CRP in midlife appeared similar to that of people 16 years older.
Participants with consistently high CRP levels at all visits also had greater white matter structural abnormalities, but only after researchers accounted for people who dropped out due to death or other factors.
Important Link
"These results suggest that increasing and persistent inflammation in the decades spanning middle-to late-life may promote white matter disease in older adults," according to the researchers, led by Keenan A. Walker, PhD, postdoctoral fellow in the department of neurology at the Johns Hopkins University School of Medicine.