Occupational Noise Exposure, Cardiovascular Risk, and Biological Stress Mediators Among Industrial Workers in South West Nigeria: A Pathway Analysis Study

The biological pathways linking chronic occupational noise exposure to cardiovascular disease risk are incompletely characterized in African populations, where genetic and environmental effect modifiers may produce different pathway dynamics than those documented in European cohorts. This doctoral study examined the relationships between occupational noise exposure, cardiovascular risk markers, and biological stress mediators among industrial workers in Ogun and Lagos States, South West Nigeria, using structural pathway analysis. An analytical cross-sectional study with biological sampling enrolled 450 industrial workers with documented high noise exposure and 200 unexposed controls. Noise exposure was quantified using personal dosimetry and noise exposure history reconstruction. Cardiovascular risk markers included blood pressure, fasting lipids, fasting glucose, high-sensitivity CRP, and carotid intima-media thickness measured by ultrasound. Biological stress mediators assessed included salivary cortisol, urinary catecholamines, interleukin-6, and oxidative stress markers (8-isoprostane). Structural equation pathway modeling demonstrated that noise-induced sympathoadrenal activation (elevated catecholamines) mediated 44.7 percent of the noise-blood pressure association, while neuroendocrine-inflammatory pathway mediation via cortisol and IL-6 accounted for an additional 22.3 percent. Oxidative stress moderated pathway magnitude at high exposure doses. The study provides original biological pathway evidence for the noise-cardiovascular risk relationship in a Nigerian industrial cohort, addressing a significant gap in global occupational cardiology literature. Recommendations include biological noise stress monitoring programs, engineering noise controls, and cardiovascular surveillance for high-noise exposed workers. Keywords: noise exposure, cardiovascular risk, stress mediators, biological pathways, South West Nigeria.