Effects of Hypoxia on the Characteristics of Auditory Perception in Humans

Auditory function in humans at high altitude. A scoping review

“…The six studies measuring PTA in this scoping review [ 10 , 11 , 36 , 37 , 42 , 43 ] almost consistently showed that HA induced alterations in hearing thresholds, although with differences in magnitude and frequency-dependence. Among variability factors, the six studies included either simulated [ 10 , 36 , 37 ] and real HA conditions [ 11 , 42 , 43 ], with consequent differences in the exposure duration, magnitude, and in the pattern of exposure (e.g., single sessions versus intermittent hypoxia).…”

“…The six studies measuring PTA in this scoping review [ 10 , 11 , 36 , 37 , 42 , 43 ] almost consistently showed that HA induced alterations in hearing thresholds, although with differences in magnitude and frequency-dependence. Among variability factors, the six studies included either simulated [ 10 , 36 , 37 ] and real HA conditions [ 11 , 42 , 43 ], with consequent differences in the exposure duration, magnitude, and in the pattern of exposure (e.g., single sessions versus intermittent hypoxia). Focusing on in-field studies [ 43 ], prolonged exposure (1 year) to an altitude higher than 3000 m induced a statistically significant deterioration in hearing thresholds at frequencies in the range 500Hz—4 kHz, with one third of participants showing an hearing threshold augment > 5 dB.…”

“…In five studies conditions of HH were simulated, while the remaining four studies were performed under NH. Three studies (two in HH [ 10 , 36 ] and one in NH [ 37 ]) used PTA, one study in HH analyzed OAE [ 13 ], and five studies (two in HH [ 12 , 14 ] and three in NH [ 2 , 38 , 39 ]) analyzed AER. All these studies had an exposure time of less than six hours.…”

“…A significant reduction of ear sensitivity (i.e., increase of the hearing threshold) was detected at the 4000 Hz frequency in both HH (p<0.001) and HN (p<0.03) versus MSL for non-corrected data, but statistical significance was lost (p = 0.08) when corrected data were considered. Ogorodnikova et al analyzed the effects of NH on PTA as well as on psychophysical properties of auditory analysis and short auditory memory [ 37 ]. In the study, 33 healthy subjects were alternatively exposed to control conditions, a single 15 min session of NH at 10.9–11.2% oxygen concentration (~5000 m), or to sessions of interval hypoxic training (IHT) over a period of 1.5 months.…”

“…Although the available evidence does not allow to perform a punctual comparison of HH versus NH effects on PTA, the studies in the present review consistently reported an increase in hearing threshold in both conditions. The sole exception was the condition of IHT in NH in [ 37 ], where the authors reported a decrease of hearing threshold and a tendency toward improved auditory sensitivity. However, this result is likely related to the spatio-temporal pattern of IHT instead of to the normobaric condition, since normobaric SSH in the same study produced an increase (albeit non-significant) in auditory threshold.…”