Obesity and aging are both linked to chronic, low-grade inflammation in the body. A new study suggests that this inflammation may help explain why poorer metabolic health is often associated with cognitive decline later in life.
In research published in the Journal of Alzheimer’s Disease, scientists analyzed data from more than 500 older adults enrolled in Canada’s Comprehensive Assessment of Neurodegeneration and Dementia study. Participants included people with dementia, mild cognitive impairment and no cognitive impairment, allowing researchers to examine how inflammation varied across different stages of brain health.
They found that elevated inflammation was far more common among participants with cognitive impairment than among those who were cognitively healthy. Roughly two-thirds of people with cognitive impairment showed higher inflammation levels, compared with about one-third of cognitively healthy adults.
The study also found that obesity was the strongest lifestyle-related factor associated with higher inflammation. While diet quality and sleep played roles, excess body weight had a larger influence on inflammatory levels than either factor alone.
Chronic low-grade inflammation, sometimes called “inflammaging,” tends to increase with age and is influenced by metabolic health, cardiovascular disease and body composition. Although the inflammation measured in this study occurred outside the brain, researchers suggest it may still contribute to changes in brain structure and function over time.
The researchers emphasize that their findings do not prove inflammation causes dementia. Instead, inflammation may serve as an early warning signal, reflecting broader metabolic strain that also affects the brain. Among participants living with dementia, those with vascular conditions showed especially high inflammation levels, further highlighting the overlap between metabolic and cognitive health.
Because many contributors to inflammation are modifiable, including obesity and cardiometabolic health, the findings may help guide earlier identification of people at higher risk for cognitive decline. Whether directly targeting inflammation can slow or prevent dementia remains unclear and will require further study.
This research was supported by the Canadian Institutes of Health Research through its funding of the Canadian Consortium on Neurodegeneration in Aging, with additional support from Brain Canada, the Alzheimer’s Society of Canada, the Women’s Brain Health Initiative, the Picov Family Foundation, the New Brunswick Health Research Foundation and the Ontario Brain Institute.