Effects of Occupational Noise Exposure on 24-Hour Ambulatory Vascular Properties in Male Workers

BACKGROUND Epidemiologic studies have demonstrated that occupational noise exposure is associated with hypertension, but the related mechanism in vascular structural changes is unclear. OBJECTIVE This panel study aimed to investigate effects of occupational noise exposure on ambulatory vascular structural properties in male workers. METHODS We recruited 20 volunteers and divided them into a high-noise-exposure group of 15 and a low-noise-exposure group of 5 based on environmental noise measurement in an automobile manufacturing company. We determined individual noise exposure and measured personal ambulatory vascular property parameters simultaneously during 24 hr. Linear mixed-effects regression models were used to estimate transient and sustained effects of noise exposure on vascular parameters by adjusting some confounders collected from self-administrated questionnaires and health checkups. RESULTS The high-noise-exposed (85 +/- 8 dBA) workers had significantly higher systemic vascular resistance (SVR) than the low-noise-exposed workers (59 +/- 4 dBA) during work and sleep periods. Contrarily, low-noise-exposed workers had significantly higher brachial artery compliance (BAC), brachial artery distensibility (BAD), and systemic vascular compliance (SVC; marginal, p = 0.07) than high-noise-exposed workers during off-duty periods. We also found that high-noise-exposed workers had significantly lower BAC (1.38 +/- 0.55 %mL/mmHg) and BAD (1.29 +/- 0.51 %/mmHg), as well as lower SVC (0.24 +/- 0.10 mL/L/mmHg), but higher SVR (1.93 +/- 0.67 mL/L/min) compared with low-noise-exposed workers over a 24-hr period. CONCLUSIONS Our findings suggest that in automobile workers, occupational noise exposure may have sustained, not transient, effects on vascular properties and also enhances the development of hypertension.