Obesity and aging: Baycrest study links inflammation to cognitive decline

Obesity and older age are strongly associated with low-grade inflammation in the body, a condition that appears closely linked to cognitive decline and dementia.

A new Baycrest study found that participants with elevated inflammation levels make up roughly two‑thirds of those with cognitive impairment, compared with only about one‑third of cognitively healthy adults, suggesting that systemic inflammation may play an important role in the cognitive changes that often accompany aging. The findings point to lifestyle factors that influence inflammation as potential targets for early risk reduction.

Often referred to as “inflammaging,” chronic low-grade inflammation gradually increases with age and contributes to vulnerability to age-related diseases, including dementia. While inflammation tends to rise naturally over time, its severity is strongly influenced by factors such as body weight, cardiovascular health and other aspects of physical health. Over time, this persistent inflammation, even when it occurs outside the brain, may contribute to changes in brain function.

“This study provides new evidence that systemic inflammation, shaped by lifestyle and overall health, may be a key mechanism connecting physical health to long-term brain function,” says Dr. Bruna Seixas-Lima, Scientific Associate at Baycrest’s Rotman Research Institute and lead author of the study, titled “Peripheral inflammation in a Canadian cohort of neurodegenerative conditions: Occurrence, determinants, and impact,” recently published in the Journal of Alzheimer’s Disease.

This is the first study to examine inflammation levels across a large and diverse group of older adults living with different forms of dementia, mild cognitive impairment and no cognitive impairment. Participants were drawn from the Comprehensive Assessment of Neurodegeneration and Dementia Study (COMPASS-ND), part of the Canadian Consortium on Neurodegeneration in Aging (CCNA).

This uniquely diverse cohort allowed researchers to examine how lifestyle and health factors contribute to inflammaging across a wide range of real-world cognitive and medical conditions. While diet quality and sleep also influenced inflammation, obesity emerged as the strongest contributor.

Extensive data were collected from 514 participants and included measures of systemic inflammation, age and sex, cardiovascular and medical history, lifestyle factors such as diet, sleep, smoking and body weight, cognitive assessments and changes in brain white matter observed through magnetic resonance imaging (MRI).

Main study findings:

• Elevated inflammation was more common and more pronounced in participants with cognitive impairment.
• Obesity was the strongest lifestyle-related contributor to inflammation, exceeding the influence of diet and sleep quality.
• Among individuals living with dementia, those with vascular conditions showed higher levels of inflammation.
• Many contributors to inflammation in aging adults are modifiable through changes in habits and lifestyle.

COMPASS-ND is one of the world’s most detailed collections of health and brain data, comprising nearly 1,200 Canadians between the ages of 50 and 90 who are living with or at risk of developing dementia. The study includes individuals with mixed dementia, multiple health conditions, complex diagnoses and frailty, reflecting real-world aging and cognitive decline. COMPASS-ND is the signature observational cohort study of the CCNA, Canada’s largest dementia research initiative, headquartered at Baycrest.

While it remains unclear whether directly treating inflammation can prevent dementia, these findings may help inform strategies for earlier identification of risk and prevention. The research team is currently conducting follow-up studies to further explore the relationship between inflammation and cognitive decline.

Reference:

Seixas-Lima B, Rosa-Neto P, Phillips NA, et al. Peripheral inflammation in a Canadian cohort of neurodegenerative conditions: Occurrence, determinants, and impact. Journal of Alzheimer’s Disease. 2025;109(2):1020-1035. doi:10.1177/13872877251401611