This longitudinal study in the Health and Retirement Study investigated how immune cell composition and aging biomarkers relate to cognitive and physical decline beyond standard inflammation markers. While it is known that inflammation influences aging, the specific impact of different immune cells on the brain versus the body over time has remained unclear due to a lack of long-term data. Analyzing data from over 7,500 participants tracked from 2016 through 2020, researchers found that cognitive and physical aging follow distinct biological paths. Higher albumin levels were associated with better outcomes for both, but other markers were more specialized: high NLR and certain “naive” CD8+ T-cells specifically predicted lower cognitive scores, whereas physical disability was primarily linked to the accumulation of “memory” CD8+ T-cells. These findings suggest that because the brain and body have different immune drivers, clinicians may need to monitor specific cell types rather than general inflammation to accurately assess a patient’s unique health risks during aging.