Environmental Microbial Exposure, Immune Activation, and Mood Variability among Urban vs. Rural Filipino Populations

Yue Hu

doi:10.54097/a2z2ma07

Authors

Yue Hu

DOI:

https://doi.org/10.54097/a2z2ma07

Keywords:

Biodiversity, Psychoneuroimmunology, TNF-α, PHQ-9, PANAS, Urbanicity, Philippines

Abstract

Background: The biodiversity hypothesis and the microbiota–immune–brain (MIB) axis posit that reduced environmental microbial contact in urban settings elevates inflammatory tone and worsens mood. Methods: In a cross-sectional comparison of Filipino adults (n=200; Quezon City [QC] urban=100, Nueva Ecija [NE] rural=100), we quantified standardized air/dust exposure indices (Shannon, Simpson, log10 CFU, EMDE_z), serum cytokines by ELISA (IL-1β, TNF-α; BSL-2), and mood (PHQ-9, PANAS), adjusting for age, BMI, SES quartiles, PSQI, and smoking. Analyses used Welch t tests, Pearson’s r, and OLS with HC3 errors; mediation was tested with 1,000 bias-corrected bootstraps. Results: Microbial diversity was lower in QC than NE (Shannon M=2.59 vs 3.27; t=−14.30, p<.001; g=−2.01), while pro-inflammatory cytokines were higher in QC (lnIL-1β M=1.438 vs 0.793, t=10.87, p<.001, g=1.53; lnTNF-α M=1.933 vs 1.389, t=11.27, p<.001, g=1.59). Diversity inversely correlated with inflammation (e.g., Shannon–lnIL-1β r=−0.719; Shannon–lnTNF-α r=−0.665; all p<.001), and inflammation tracked mood (lnTNF-α with PHQ-9 r=0.776; with PANAS-NA r=0.785; with PANAS-PA r=−0.487; all p<.001). In mediation, Shannon predicted lower lnTNF-α (a=−0.512, p<.001), which predicted higher PHQ-9 (b=4.618, p<.001); the indirect effect was significant (a×b=−2.366, 95% CI −2.945 to −1.800), with a residual direct effect (c′=−0.516, p<.001). Conclusions: Higher environmental microbial diversity is associated with dampened inflammatory activity and lower depressive burden, supporting a bio-ecological pathway linking urbanicity, immunity, and affect. Findings suggest biodiversity-aware urban design as a mental-health–relevant policy lever.

Downloads

Download data is not yet available.

References

[1] Haahtela T, Holgate S, Pawankar R, et al. The biodiversity hypothesis and allergic disease. World Allergy Organ J. 2013;6:3.

[2] Rook GAW. Regulation of the immune system by biodiversity from the natural environment. Proc Nutr Soc. 2013;72(4):497–504.

[3] Hanski I, von Hertzen L, Fyhrquist N, et al. Environmental biodiversity, human microbiota, and allergy are interrelated. PNAS. 2012;109(21):8334–8339.

[4] Dantzer R, O’Connor JC, Freund GG, Johnson RW, Kelley KW. From inflammation to sickness and depression. Nat Rev Neurosci. 2008;9(1):46–56.

[5] Miller AH, Raison CL. The role of inflammation in depression. Nat Rev Immunol. 2016;16(1):22–34.

[6] Kroenke K, Spitzer RL, Williams JBW. The PHQ-9: validity of a brief depression severity measure. J Gen Intern Med. 2001;16(9):606–613. Watson D, Clark LA, Tellegen A. Development and validation of PANAS. J Pers Soc Psychol. 1988;54(6):1063–1070.

[7] Hayes AF. Introduction to Mediation, Moderation, and Conditional Process Analysis. 2nd ed. Guilford Press; 2018.

[8] Twohig-Bennett C, Jones A. The health benefits of the great outdoors: a systematic review and meta-analysis of greenspace exposure and health outcomes. Environ Res. 2018;166:628–637.