Relations of residential greenness with immunity and inflammation.
Level 4 - case-series / case-control
Cross-sectional analysis of baseline observational cohort data
PubMed 41831756 · doi:10.1016/j.envres.2026.124256
What was done
Researchers analyzed baseline cross-sectional data from 624 adult participants (aged 25–70 years) in Louisville, Kentucky, enrolled in the Green Heart Study (2018–2019). Residential greenness around homes was quantified via leaf area index and NDVI within 100-m and 500-m buffers. Linear regression models adjusted for sociodemographic and behavioral factors were used to evaluate associations between greenness and circulating immune cell counts and cytokines.
What was found
The sample was 77.4% White and 59% female. Leaf area within a 100-m buffer was negatively associated with circulating levels of B cells (-11.6% per IQR; 95% CI: -16.6 to -6.3), monocytes (-4.7% per IQR; 95% CI: -8.9 to -0.3), and natural killer cells (-5.1% per IQR; 95% CI: -9.3 to -0.6). Greenness was positively associated with interleukin-4 (IL-4) (9.8% per IQR; 95% CI: 3.3 to 16.7). Other cytokines showed no consistent associations.
Why it matters
This study links residential greenness directly to alterations in circulating immune cell populations and immunoregulatory cytokines, identifying potential biological pathways for the health benefits associated with natural environments.
Limits
The analysis is cross-sectional and cannot establish causality. The study population was from a single geographic location and predominantly White (77.4%), limiting generalizability. Residual confounding from unmeasured environmental or lifestyle factors cannot be ruled out.
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