Abstract
ObjectiveWe aimed to assess the effect of noise exposure on bottom-up and top-down attention functions in industrial workers based on behavioral and brain responses recorded by the multichannel electroencephalogram (EEG).MethodIn this cross-sectional study, 563 shipyard noise-exposed workers with clinical normal hearing were recruited for cognitive testing. Personal cumulative noise exposure (CNE) was calculated with the long-term equivalent noise level and employment duration. The performance of cognitive tests was compared between the high CNE group (H-CNE, >92.2) and the low CNE group; additionally, brain responses were recorded with a 256-channel EEG from a subgroup of 20 noise-exposed (NG) workers, who were selected from the cohort with a pure tone threshold <25 dB HL from 0.25 to 16 kHz and 20 healthy controls matched for age, sex, and education. P300 and mismatch negativity (MMN) evoked by auditory stimuli were obtained to evaluate the top-down and bottom-up attention functions. The sources of P300 and MMN were investigated using GeoSource.ResultsThe total score of the cognitive test (24.55 ± 3.71 vs. 25.32 ± 2.62, p < 0.01) and the subscale of attention score (5.43 ± 1.02 vs. 5.62 ± 0.67, p < 0.001) were significantly lower in the H-CNE group than in the L-CNE group. The attention score has the fastest decline of all the cognitive domain dimensions (slope = −0.03 in individuals under 40 years old, p < 0.001; slope = −0.06 in individuals older than 40 years old, p < 0.001). When NG was compared with controls, the P300 amplitude was significantly decreased in NG at Cz (3.9 ± 2.1 vs. 6.7 ± 2.3 μV, p < 0.001). In addition, the latency of P300 (390.7 ± 12.1 vs. 369.4 ± 7.5 ms, p < 0.001) and MMN (172.8 ± 15.5 vs. 157.8 ± 10.5 ms, p < 0.01) was significantly prolonged in NG compared with controls. The source for MMN for controls was in the left BA11, whereas the noise exposure group's source was lateralized to the BA20.ConclusionLong-term exposure to noise deteriorated the bottom-up and top-down attention functions even in the absence of threshold shifts, as evidenced by behavioral and brain responses.
Highlights
Noise is one of the most common types of pollution in both occupational and non-occupational environments [1]
When noise-exposed group (NG) was compared with controls, the P300 amplitude was significantly decreased in NG at Cz (3.9 ± 2.1 vs. 6.7 ± 2.3 μV, p < 0.001)
We aimed to evaluate the effect of noise exposure on bottom-up and top-down attention functions in industrial workers in the absence of peripheral hearing loss based on behavioral and brain responses recorded by the multichannel electroencephalogram (EEG)
Summary
Noise is one of the most common types of pollution in both occupational and non-occupational environments [1]. Longterm noise exposure that exceeds certain levels can harm the auditory system, resulting in progressive hearing loss and an increase in hearing sensitivity threshold [2, 3]. Evidence of the non-auditory effects related to noise exposure is growing [4, 5], such as, annoyance [6], disturbed sleep [7], cardiovascular disease [8], and anxiety [9]. In addition to these effects, noise exposure affects a variety of cognitive processes, such as reaction time, memory, perception, and attention [10]. A previous study demonstrated that noise exposure could impair performance on the focused attention task [12], while some studies found that noise could increase arousal levels and accuracy in computerized attention tests [13]. The effect of noise exposure on attention performance remain rather inconclusive [14, 15]
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