Hearing loss in space

Background. Temporary and, in some cases, permanent hearing loss has been d ocumented after long-duration spaceflights. Methods. We examined all existi ng published data on hearing loss after space missions to characterize the losses. Results. Data from Russian missions suggest that the hearing loss, when it occurs, affects mainly mid to high frequencies and that using heari ng protection often might prevent the loss. Several significant questions r emain about hearing loss in space. While the hearing loss has been presumed to be noise-induced, no clear link has been established between noise expo sure and hearing loss during spaceflight. In one documented case of tempora ry hearing loss from the Shuttle-Mir program, the pattern of loss was atypi cal for a noise-induced loss. Continuous noise levels that have been measur ed on the Mir and previous space stations, while above engineering standard s, are not at levels usually associated with hearing loss in ground-based s tudies (which have usually been limited to 8-10 h exposure periods). Attemp ts to measure hearing in space using threshold-based audiograms have been u nsuccessful in both the American and Russian programs due to noise interfer ence with the measurements. Conclusions: The existing data highlight the ne ed for reliable monitoring of both hearing and noise in long-duration space flight.