Micronutrients to Prevent Noise-induced Hearing Loss

Phase 2

Completed

Interventions: Other: Placebo
Drug: beta-carotene, vitamins C and E, magnesium

Brief Summary: Noise-induced hearing loss (NIHL) is a significant clinical, social, and economic issue. Studies in animals have allowed us to identify mechanisms contributing to NIHL, including direct mechanical trauma, free radicals formed in association with metabolic stress, and reduced blood flow. A combination of antioxidant vitamins (beta-carotene, and vitamins C and E) and the mineral magnesium (which acts in part as a vasodilator but also as an antioxidant) is highly effective in preventing NIHL in animals. These studies evaluate efficacy of this intervention in humans.

Hypothesis: Treatment with these micronutrients provides safe, effective attenuation of acute hearing changes induced by exposure to real-world sounds producing temporary (non-permanent) or permanent hearing changes induced by exposure to real-world sounds.

Experiment 1: "Digital Audio Player" studies (University of Florida, Gainesville). Prevention of \*temporary\* elevations in hearing thresholds, induced by exposure to moderately loud music, will be measured. Subjects will be 70 young adults with equal numbers of male and female participants.

Detailed Description: This study assessed the potential for prevention of the temporary changes in hearing that can occur after use of a music player device for 4 hours. All participants listened to one of two playlists (pop or rock) set at the same volumes to provide equivalent and consistent exposures across participants. Participants received either a dietary supplement or a placebo once/daily for three days prior to the day of music exposure, and also on the day of music exposure. The fourth and final dose was consumed immediately prior to music listening and consumption was observed by a member of the study team. Changes in hearing were assessed 15-min post-music, and then 1, 2, and 3 hours later, as well as the following day and 1 week later.

Recruitment & Eligibility

Inclusion Criteria

Hearing inclusion criteria are as follows for all studies:

subjects must have a normal audiologic assessment at baseline consisting of:
1. symmetric hearing with air conduction thresholds no worse than 25 dB HL at tested frequencies between .25 - 8 kHz;
2. no significant threshold asymmetry (i.e., greater than 15 dB) between the ears at any test frequency;
3. no significant air-bone gaps (i.e., greater than 10 dB); and
4. Type A tympanograms bilaterally, defined as a range of -140 to +40 daPa based on the 90% range for adults (Margolis & Hunter 2000).

Additional criteria are as follows:

No history of ear disease, able to provide informed consent, agree to follow study procedures, normal health screening at study entry

Exclusion Criteria

Arm && Interventions

Group	Intervention	Description
Placebo for nutrients	Placebo	Subjects in University of Florida music player study who are assigned to control (placebo) condition. Placebo tablets are consumed for 4 days.
Nutrients	beta-carotene, vitamins C and E, magnesium	Subjects in University of Florida music player study who are assigned to nutrient condition(beta-carotene, vitamins C and E, magnesium). Nutrient tablets are consumed for 4 days.

Primary Outcome Measures

Name	Time	Method
Average Threshold Shift at 4 kHz in Both Ears	15 min, 1 hr intervals for 3 hours to measure temporary changes; additional tests at 1 day and 1 week post-exposure.	The study measures the quietest decibel level the participants can hear before the 4 hour music exposure The first post-music test to measure shift is 15 minutes after the music exposure is completed and again at 1 hour intervals. The shift represents the mean change in quietest decibel volume detected between baseline (pre-music) and post music.

Secondary Outcome Measures

Name	Time	Method
Threshold Shift at Individual Frequencies, Including 0.25, 0.5, 1, 2, 3, 6, and 8 kHz, 15 Min Post-music	15 min	The study measures the quietest decibel level the participants can hear before the 4 hour music exposure The first post-music test to measure shift is 15 minutes after the music exposure is completed and again at 1 hour intervals. The shift represents the mean change in quietest decibel volume detected between baseline (pre-music) and post music.
Tinnitus	immediate, repeated measures at 1 hr intervals for 3 hours to measure temporary changes; additional tests at 1 day and 1 week post-exposure.	Presence of tinnitus was assessed using yes/no question. If tinnitus was reported, perception was assessed using survey.