Short-term exposure to noise on stroke volume and left ventricular contractility: A repeated-measure study

Prolonged exposure to noise has been associated with cardiovascular disease, but the possible mechanism for its influence on cardiac activity is unknown. This study investigated the acute effects of noise exposure on 24-h ambulatory cardiac parameters among male workers. We recruited 75 volunteers in an aviation-industry cohort in 2009. Personal noise-exposure levels and individual cardiac parameters, including stroke volume (SV) and left ventricular contractility (LVC), were measured simultaneously over 24 h on working and nonworking days. Linear mixed-effects regression models were used to estimate transient and sustained effects on ambulatory SV and LVC among high-noise-exposure (≥80 A-weighted decibels [dBA]), low-noise-exposure (<80 dBA) and office workers. Every 1-dBA increase in noise exposure was significantly associated with transient changes of -1.50 (95% confidence interval [CI]: -2.18, -1.03) ml/beat in SV and -1.76 (-2.99, -1.03) L/sec in LVC at work on working days only among high-exposure workers. The 1-dBA increase in nocturnal noise exposure was also significantly associated with transiently decreased SV among high-exposure (-1.62 [-2.15, -1.22] ml/beat), low-exposure (-1.27 [-1.57, -1.03] ml/beat) and office workers (-1.09 [-1.18, -1.00] ml/beat), but only the high-exposure group had the transiently reduced LVC (-1.70, [-2.37, -1.22] L/sec) after the current noise exposure on nonworking days. Such decreasing effects persisted to become sustained decreases in 24-h ambulatory SV in high-exposure (-1.10 [-1.20, -1.01] ml/beat) and office workers (-1.13 [-1.22, -1.05] ml/beat) on working days and in all three groups (-1.19 [-1.36, -1.04]; -1.15 [-1.31, -1.02]; -1.08 [-1.13, -1.02] ml/beat, respectively) on nonworking days. No significant effect on 24-h ambulatory LVC was found in any group on working or nonworking days. Occupational and nocturnal noise exposure may have acute effects on 24-h ambulatory SV among male workers, directly influencing the cardiac function related to cardiovascular disease.