Gender Differences and Occupational Risk Factors in Noise-Induced Cardiovascular Responses Among Grain Milling Machine Operators in Nigeria

Abstract

Occupational noise is one of the most widespread yet least regulated hazards facing informal-sector workers in low- and middle-income countries, and its cardiovascular consequences are increasingly difficult to ignore. While the auditory harm caused by loud machinery is well recognised, far less is known about how sustained occupational noise reshapes blood pressure and heart rhythm, and whether that reshaping differs between men and women who share the same working environment. This study set out to answer that question among grain milling machine operators in Nigeria, a workforce that operates almost entirely outside formal occupational-health oversight. A cross-sectional design was used to examine 120 operators (80 men and 40 women), with data gathered on age, years of work experience, use of ear protection, systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse rate. Male operators recorded consistently higher mean SBP and DBP than their female counterparts, although women who had spent many years at the mill showed a comparable rise in cardiovascular strain, suggesting that sex differences narrow with cumulative exposure. Work experience emerged as the strongest correlate of cardiovascular strain (SBP: r = 0.62; DBP: r = 0.58; pulse rate: r = 0.49, all p < 0.05), pointing to a clear cumulative-dose relationship. Operators without ear protection showed measurably higher blood pressure and pulse rate than those who used it. Taken together, the findings position occupational noise as a significant, modifiable cardiovascular risk factor within Nigeria's informal milling sector, with sex acting as a moderating rather than protective influence.