Dietary supplement comprised of β-carotene, vitamin C, vitamin E, and magnesium: failure to prevent music-induced temporary threshold shift

Abstract

This study examined potential prevention of music-induced temporary threshold shift (TTS) in normal-hearing participants. A dietary supplement composed of β-carotene, vitamins C and E, and magnesium was assessed using a randomized, placebo-controlled, double-blind study design. Dosing began 3 days prior to the music exposure with the final dose consumed approximately 30-min pre-exposure. There were no group differences in post-exposure TTS or music-induced decreases in distortion product otoacoustic emission (DPOAE) amplitude. Transient tinnitus was more likely to be reported by the treatment group, but there were no group differences in perceived loudness or bothersomeness. All subjects were monitored until auditory function returned to pre-exposure levels. Taken together, this supplement had no effect on noise-induced changes in hearing. Recommendations for future clinical trials are discussed.

Keywords: digital audio player; distortion product otoacoustic emission; magnesium; temporary threshold shift; tinnitus; vitamin C; vitamin E; β-carotene.

Figures

Figure 1

A-1F. Change from the baseline threshold (mean+SEM) measured immediately prior to music exposure was measured at 15 min post-music (1A), 1 hour and 15 min post music (1B), 2 hours and 15 min post music (1C), 3 hours and 15 min post music (1D), 1 day post music (1E), and 1 week post music (1F). Subjects that had threshold differences outside of the expected test-retest reliability criteria were retested 1 week later. All subjects were confirmed to return to their pre-study functional baseline. *Asterisks indicate statistically significant group difference (p

Figure 2

Variability from test 1, completed at screening, to test 2, completed prior to the music exposure, is shown in Figure 2A. Negative values indicate performance was better on the second pre-music test; the green line indicates the conventional −5 dB reliability assumption. Positive values indicate performance was poorer on the second pre-music test; the red line indicates the conventional +5 dB reliability assumption. Reliability of the 70 subjects shown here was consistent with that reported for 66 subjects tested by Spankovich et al. [2014] (Fig. 2B) and that of the 33 subjects tested by Le Prell et al. [2012] (Fig. 2C). Because some symbols are hidden behind others, data value frequencies are listed in table 1. The average test-retest difference is near zero (Fig. 2D) as there are equal numbers of subjects that perform better, versus those that perform more poorly, on the second test. The average of the absolute value of the test to test difference is ~3-dB with standard deviations indicating that the majority of subjects are consistent within 5–6 dB from test to test.

Figure 3

Distortion product otoacoustic emission (DPOAE) amplitude was assessed before and after music exposure for subjects; screening, pre-music baseline, 15 min-post music, 1 hour and 15 min post music, 2 hours and 15 min post music, 3 hours and 15 min post music, 1 day post music, and 1 week post music, are shown for the placebo and the supplement groups at 2 kHz (3A, 3B), 3 kHz (3C, 3D), 4 kHz (3E, 3F), 6 kHz (3G, 3H), and 8 kHz (3I, 3J). Noisefloor data are averaged across all subjects and all test times with a single noise floor value shown for each frequency. There was no effect of treatment assignment on the change in DPOAE amplitude.

Figure 4

Among participants reporting tinnitus, there was no reliable difference in the average tinnitus loudness rating (4A) or bothersomeness rating (4B). There were a total of 19 participants (54.3%) in the treatment group who reported tinnitus at one or more test times after the music exposure, compared to a total of 9 participants (25.7%) in the placebo group; there were significantly more participants reporting tinnitus in the supplement group than in the placebo group.