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.
Experiment 2: "Urban warfare" military studies (Karolinska Institutet, Sweden). Prevention of *temporary* elevations in hearing thresholds, induced by automatic gunfire sound inside a concrete bunker, will be measured. Subjects will be 31 adult male or female officers in the Swedish army required to participate in urban combat training regardless of study participation. All subjects are required to wear standard hearing protection during combat exercises.
Estimated Enrollment: 101
Study Start Date: October 2008
Estimated Primary Completion Date: June 2013 (Final data collection date for primary outcome measure)