Association of Behavior With Noise-Induced Hearing Loss Among Attendees of an Outdoor Music Festival: A Secondary Analysis of a Randomized Clinical Trial

Key Points

Question  What factors are associated with temporary noise-induced hearing loss after music exposure during a music festival?

Findings  In this post hoc secondary analysis of 51 participants in a randomized clinical trial, a temporary threshold shift across 3.0 and 4.0 kHz was associated with the following participant-related factors: not using earplugs, use of alcohol and/or drugs, and male sex.

Meaning  Male attendees of music festivals who do not use earplugs and simultaneously use alcohol and/or drugs are more likely to develop temporary noise-induced hearing loss.

Importance  To date, factors associated with noise-induced hearing loss at music festivals have not yet been analyzed in a single comprehensive data set. In addition, little is known about the hearing loss–associated behavior of music festival attendees.

Objectives  To assess which factors are associated with the occurrence of a temporary threshold shift (TTS) after music exposure and to investigate the behavior of music festival attendees.

Design, Setting, and Participants  This prospective post hoc analysis gathered data from a randomized, single-blind clinical trial conducted on September 5, 2015, at an outdoor music festival in Amsterdam, the Netherlands. Adult volunteers with normal hearing were recruited via social media from August 26 through September 3, 2015. Intention to use earplugs was an exclusion criterion. Of 86 volunteers assessed, 51 were included. This post hoc analysis was performed from October 3, 2016, through February 27, 2017.

Interventions  Music festival visit for 4.5 hours.

Main Outcomes and Measures  The primary outcome was a TTS on a standard audiogram for the frequencies 3.0- and 4.0-kHz. Multivariable linear regression was performed to determine which factors are associated with a TTS. A questionnaire on behavior, hearing, and tinnitus was distributed to the participants before and after the festival visit.

Results  A total of 51 participants were included (18 men [35%] and 33 women [65%]) with a mean (SD) age of 27 (6) years. Mean (SD) threshold change across 3.0 and 4.0 kHz was 5.4 (5.7) dB for the right ear and 4.0 (6.1) dB for the left ear. Earplug use (absolute difference in the left ear, −6.0 dB [95% CI, −8.7 to −3.2 dB]; in the right ear, −6.4 dB [95% CI, −8.8 to −4.1 dB]), quantity of alcohol use (absolute difference per unit in the left ear, 1.1 dB [95% CI, 0.5 to 1.7 dB]; in the right ear, 0.7 dB [95% CI, 0.1 to 1.4 dB]), drug use (absolute difference in the right ear, 6.0 dB [95% CI, 0.9 to 11.1 dB]), and male sex (absolute difference in the right ear, 4.1 dB [95% CI, 0.3 to 5.9 dB]) were independently associated with hearing loss, with earplug use being the most important factor. Unprotected participants reported significantly worse subjective hearing performance and tinnitus after the festival visit than did participants using earplugs (Cramer V, 0.62 [95% CI, 0.47-0.79] and 0.39 [95% CI, 0.16-0.62], respectively). In the earplug group, the perceived loudness (r = −0.72; 95% CI, −1.00 to −0.43) and appreciation (r = 0.53; 95% CI, 0.29 to 0.78) of music and speech perception (r = 0.21; 95% CI, 0.09 to 0.35) were correlated with the duration of earplug use.

Conclusions and Relevance  The present study identified nonuse of earplugs, use of alcohol and drugs, and male sex as associated with a TTS at an outdoor music festival. Physicians should consider these factors to raise awareness about the combined risk of attending music festivals without using earplugs while consuming alcohol and/or drugs. The intention to use earplugs was correlated with the loudness and appreciation of music with earplugs, which may advocate for the use of personalized earplugs.

Trial Registration  trialregister.nl Identifier: NTR5401

During the past 2 decades, the prevalence of hearing loss among young people has increased, partly owing to the increasing popularity of visiting music concerts, clubs, and festivals.^1,2 Noise-induced hearing loss (NIHL) due to recreational noise exposure may be reduced by using earplugs that decrease the loudness of the noise.³ Recently, a randomized clinical trial (RCT) on the effect of earplugs on recreational NIHL⁴ found that significantly fewer temporary threshold shifts (TTSs) after a 4.5-hour festival visit were objectified in participants who used earplugs compared with participants who did not.

Development of NIHL due to recreational noise exposure depends on factors concerning the noise, including the duration of exposure, the intensity and frequency of the noise and how fast the sound pressure level increases.^5,6 In addition, inner ear vulnerability to noise after equivalent noise exposure varies greatly, suggesting that additional factors are associated with individual susceptibility to noise.^7,8 The first factor that plays a significant role in the development of NIHL is increasing age.^9-12 This association is partly biased by the cumulative noise exposure inherent to an increasing age. Second, several studies on occupational NIHL^9,10,12-14 have shown that men are more likely to develop NIHL than are women. For the same amount of occupational noise, Kovalova et al¹³ observed significantly more NIHL in men than in women. Third, alcohol intake is correlated with NIHL.^15,16 As early as 1978, an experiment was conducted that revealed that alcohol reduces the protective action of the acoustic reflex in persons with normal hearing.¹⁵ In a controlled experiment in 2007, alcohol consumption correlated with a TTS in the lower frequencies of normal-hearing participants.¹⁶ Other substances are described to influence susceptibility to NIHL as well; 2.4-methylenedioxymethamphetamine (MDMA) is a popular party drug in young adults and known for its hallucinatory, euphoric, and stimulant effect.¹⁷ In 2001, Sharma¹⁸ described a case of sensorineural hearing loss after the use of MDMA and presented ototoxicity as an adverse effect of MDMA. MDMA is known to exhaust brain neurotransmitters dopamine and serotonin, which have a protective function against acoustic trauma in the cochlea.^19-22 Similar to MDMA, cocaine blocks the reuptake of dopamine and serotonin at the presynaptic membranes.²³ A few cases of temporary severe sensorineural hearing loss after the use of cocaine or a combination of drugs are described in the literature.^24-26 Finally, smoking combined with noise exposure is hypothesized to correlate with hearing thresholds and NIHL.^27-30 A similar association between smoking cannabis and NIHL is suggested, but no corroborating studies were found.

The association of these possible factors with recreational NIHL has, to our knowledge, not been investigated in a single comprehensive data set. The aim of this study was to identify factors associated with a TTS after music exposure at an outdoor music festival. To answer this research question, data from the previous RCT on the effectiveness of earplugs in preventing recreational NIHL⁴ were used.

Despite the significant increase in NIHL, the general willingness to use earplugs, the reported use of earplugs, and knowledge of the risks of developing NIHL are low in music festival attendees.^31,32 A secondary aim of this study was therefore to analyze self-reported outcomes that may influence earplug use during a music festival. We intended to gain insights in the behavior of music festival attendees during a festival visit, including earplug use and the time spent near stages and loudspeakers as well as alcohol and drug use.

This study contains prospectively gathered data from a single-blind RCT (NTR5401) on the effect of earplugs on the occurrence of TTS.⁴ This post hoc analysis of the RCT was performed from October 3, 2016, through February 27, 2017. The medical ethics committee of the University Medical Centre Utrecht granted an exemption of full review. All participants signed an informed consent before participating.

Location of the study was an outdoor music festival in Amsterdam, the Netherlands, on September 5, 2015. Participants of the study were recruited from August 26 through September 3, 2015, via social media advertisements and offered a free ticket to the festival. After completing the study they were offered a €50 stipend. An important exclusion criterion was the intention to use earplugs because randomizing volunteers with such an intention to the unprotected group would be unethical. Other exclusion criteria included no Dutch or English language proficiency, being younger than 18 years, past ear surgery (except ventilation tubes), and present ear diseases or hearing loss.

The setup of the RCT is described in detail elsewhere.⁴ All participants attended a music festival for 4.5 hours. Half of them were instructed to use earplugs (MTV Soundkeepr; Standt BV). The time when participants left the festival terrain and the time of hearing evaluations were registered. All participants were advised to limit the use of alcohol and drugs in a way that they would be able to complete hearing evaluations after the festival visit.⁴

Before and after the festival visit, hearing evaluations took place in an adjacent studio. Air conduction audiograms for the frequencies 0.5, 1.0, 2.0, 3.0, 4.0, 6.0, and 8.0 kHz were performed, and the presence of a TTS (≥10 dB) calculated as a mean across 3.0 and 4.0 kHz was used as the primary outcome measure for NIHL.³ The threshold shift was assumed to be temporary; however, no follow-up audiometry was performed to confirm this assumption. Audiometry was completed, in compliance with international standards, by the same audiologist or audiology assistant for both ears before and after exposure in the same mobile audio cabin (350 Series Maxi Audiology Booth; IAC Medical) using an audiometer (AVANT A2D+; MedRx Inc) with a headphone (HDA200; Sennheiser Electronic Corp). Background sound level in the audio cabins was beneath maximum tolerated levels.

After the outdoor festival visit, participants completed a Dutch questionnaire concerning their behavior during the festival visit. The questionnaire included questions regarding alcohol and drug use, time spent near stages and loudspeakers, loudness of music, subjective hearing loss, and tinnitus. Participants allocated to the earplug group were asked to judge their music appraisal, understanding of speech, earplug comfort, wearing time, and intention to use earplugs again.⁴ The English translation of the questionnaire is found in the eMethods in the Supplement.

To identify factors associated with a TTS after music exposure, we performed a multivariable linear regression analysis of the influence on TTS of the following 6 factors: use of earplugs, use of alcohol, use of drugs, sex, age, and the interval from the festival to the evaluation. The independent influence of each factor was expressed as the unstandardized Pearson correlation coefficient (B), representing the influence of a 1-unit change in the factor on a 1-dB change in TTS while controlling for the effect of other variables. Furthermore, the standardized correlation coefficient (β) was provided, in which the influence of a 1-U change in the factor was standardized to range from −1 to 1 to compare the independent influence of multiple factors. The 95% CIs around the correlation coefficients are provided to describe the precision of the estimates and the plausible range for the true effect. The data were normally distributed. A stepwise design with manual backward selection procedure was chosen. Owing to the post hoc design, investigators were not blinded for the independent variables investigated.

To identify associations between outcomes on the questionnaire, we used the Spearman correlation coefficient test, for which we reported r values (range, −1.00 to 1.00) for the comparison of 2 ordinal variables and the Fisher exact test for the comparison of 1 ordinal and 1 nominal variable, for which we reported the Cramer V correlation coefficient (range, 0 [no correlation] to 1.00 [strong correlation]). The 95% CI was calculated by bootstrapping technique. All statistical analyses were performed using SPSS Statistics software (version 21; IBM Corp).

Of 86 individuals assessed for eligibility, 51 were included in the study.⁴ Twenty-five participants were assigned to use earplugs. Eighteen participants (35%) were male and 33 (65%) were female. Mean (SD) age of participants was 27 (6) years. Mean (SD) alcohol consumption was 4 (2) U (1 U represents 1 glass approximately 200-250 mL). Eleven participants used drugs during the festival visit. The mean time-averaged, equivalent A-weighted sound pressure level was 100 dBA, with outliers as high as 145 dBA.⁴ The Figure shows the audiograms before and after the festival for the earplug users and nonusers. The mean threshold shift across 3.0 and 4.0 kHz was 5.4 (5.7) dB for the right ear and 4.0 (6.1) dB for the left ear.

As a result of an audiology assistant's failure to follow study protocol, the 3.0-kHz threshold baseline data were missing. The missing 3.0-kHz threshold data were substituted by the mean of 2.0- and 4.0-kHz thresholds at baseline.³³ One participant reported having consumed alcohol but did not report the amount of units. This missing value was replaced with the mean units of the other participants who consumed alcohol. Time of hearing evaluation was missing for 1 participant and replaced with the mean time of the other participants.

As shown in Table 1, in univariable regression analysis, the use of earplugs was negatively correlated with a TTS in both ears (B = −5.78 [95% CI, −8.81 to −2.74] and −5.97 [95% CI, −8.69 to −3.24]), whereas units of alcohol (B = 1.03 [95% CI, 0.30 to 1.76] and 0.90 [95% CI, 0.20 to 1.58]) and male sex (B = 1.03 [95% CI, 0.30 to 1.76] and 4.00 [95% CI, 0.85 to 7.17]) were positively correlated with a TTS in both ears. As shown in Table 2, using a multivariable regression analysis, use of earplugs was negatively correlated (B = −5.97 [95% CI, −8.73 to −3.24] and −6.44 [95% CI, −8.80 to −4.09]) and alcohol intake positively correlated (B = 1.09 [95% CI, 0.46 to 1.72] and 5.98 [95% CI, 0.87 to 11.08]) with a TTS in both ears. Use of earplugs was associated with reduced TTS (absolute difference in the left ear, −6.0 dB [95% CI, −8.7 to −3.2 dB]; in the right ear, −6.4 dB [95% CI, −8.8 to −4.1 dB]), whereas alcohol use was associated with increased TTS (absolute difference per unit in the left ear, 1.1 dB [95% CI, 0.5 to 1.7 dB]; in the right ear, 0.7 dB [95% CI, 0.1 to 1.4 dB]) in both ears. Male sex (absolute difference, 4.1 dB [95% CI, 0.3 to 5.9 dB]) and use of MDMA (absolute difference, 6.0 dB [95% CI, 0.9 to 11.1 dB]) were positively correlated with a TTS in the right ear only. The model explained 39% of the variance for the left ear and 53% for the right ear.

Associations between questions answered by all study participants regarding their behavior during the music festival are reported in Table 3. A decrease in subjective hearing performance was related to an increase in subjective tinnitus (Cramer V, 0.40; 95% CI, 0.20-0.66). In addition, subjective hearing performance and tinnitus were correlated with earplug use (Cramer V, 0.62 [95% CI, 0.47-0.79] and 0.39 [95% CI, 0.16-0.62], respectively). Use of earplugs did not have a strong association with the reported time spent near stages and loudspeakers or with drug use. However, earplug use was correlated with increased alcohol intake (Cramer V, 0.40; 95% CI, 0.35-0.70). In addition, increased alcohol intake was positively correlated with the amount of time spent near loudspeakers (r = −0.41; 95% CI, −0.64 to −0.14]) and with drug use (Cramer’s V, 0.42; 95% CI, 0.29 to 0.72).

The associations between questions answered by the participants allocated to the earplug group are reported in Table 4. In this group, perceived loudness (r = −0.72; 95% CI, −1.00 to −0.43) and appreciation (r = 0.53; 95% CI, 0.29 to 0.78) of music and speech perception (r = 0.21; 95% CI, 0.09 to 0.35) were correlated with the duration of earplug use. The intention to wear earplugs again moderately increased when speech perception with earplugs increased (r = 0.41; 95% CI, 0.11-0.66). The intention to use earplugs again increased when the duration of earplug use during the study increased (r = 0.44; 95% CI, 0.16-0.68). Speech perception with earplugs and intention to use earplugs again was moderately correlated (r = 0.41; 95% CI, 0.11-0.66). The intention to wear earplugs again was reduced when the music was perceived as too soft while wearing earplugs (r = −0.38; 95% CI, −0.68 to −0.06). Loudness of music and comfort of earplug use could be correlated, but the CI was large (r = −0.40; −0.70 to −0.02).

The present study identified nonuse of earplugs, use of alcohol and drugs, and male sex as associated with a TTS at an outdoor music festival. Not using earplugs was correlated with reported subjective hearing loss and tinnitus. With increasing intake of alcohol, the amount of time spent near loudspeakers increased. The intention to use earplugs was associated with the loudness and appreciation of music and the speech perception with earplugs.

Not using earplugs and consumption of alcohol were identified as associated with a TTS in both ears. Male sex and use of MDMA were also identified as associated, although weaker correlations were seen in the right ear. This discrepancy between ears can be explained by the right ear having been affected more severely by the high sound pressure levels than the left ear. Our results are in accordance with previous cohort studies and case reports^10-30 on the influence of earplugs, sex, and alcohol in NIHL. The effectiveness of earplugs was examined in a systematic review³ in which 1 RCT was described that also showed a positive effect of earplugs in reducing postconcert threshold shifts. The effect of sex on NIHL was first observed in 1981, when male visitors of a pop music event exhibited larger TTSs on all frequencies than did female visitors.³⁴ With regard to alcohol consumption, Upile et al¹⁶ observed a positive association between breath alcohol concentration and the magnitude of hearing thresholds when exposed to recreational noise. Apart from the previously mentioned case report,¹⁸ the association between MDMA and NIHL was studied only in animals; a study in rats³⁵ showed that the combination of MDMA and noise enhances the effect of noise on NIHL.

Alcohol and drug use are known to occur at music festivals.^36,37 Their influence on the development of TTSs and permanent threshold shifts at a younger age enhance the effect of music on NIHL. Thus, music venue attendees are more likely to develop NIHL at a noisy music venue when using alcohol and drugs than are attendees who do not simultaneously use these substances. In the present study, 11 of 51 participants (22%) reported the use of drugs and 49 of 51 participants (96%) reported to have consumed alcohol. Because participants were advised to limit the use of substances to be able to undergo audiometry and complete the questionnaire after the festival visit, the accuracy of self-reported alcohol and drug use may be questioned. In a study on the accuracy of self-reported consumption of alcohol,³⁸ an underestimation of alcohol consumption occurred when the intake increased beyond 6 U, whereas it was reasonably accurate for light to moderate alcohol intake (<6 U). Considering the mean amount reported by our participants (4 U), we expect this possible bias to be limited and the association between alcohol and TTSs to be a significant one. As physicians, it is vital to inform patients of the combined risk of using alcohol and/or drugs and not using earplugs at music venues and strongly advise against such behavior.

The secondary aim of this study was to investigate the behavior of music festival attendees. In particular, we were interested to see whether participants who used earplugs would exhibit dangerous behavior in reference to their location at a festival, for example, near stages and loudspeakers, because of a sense of protection against the high sound pressure levels while using earplugs. We did not find an association based on the questionnaire findings. Alcohol consumption, however, was positively correlated with wearing earplugs, the amount of time spent near loudspeakers, and drug use. Thus, when participants consumed more alcohol, they exhibited more dangerous behavior. How well participants were able to estimate their location at the festival in reference to stages and loudspeakers may be questioned. In addition, earplug use was related to subjective hearing performance. Furthermore, subjective tinnitus was related to subjective hearing performance; participants who experienced newly induced tinnitus also reported worse subjective hearing performance after the festival visit. Thus, participants seem to rate hearing and tinnitus complaints equivalently.

In the earplug group, loudness and appreciation of music and speech perception while using earplugs were associated with the duration of earplug use. In previous studies,^32,39 loud music, awareness of loud music, and the appreciation of music were associated with use of earplugs. These findings may advocate the use of personalized earplugs. In addition, personal noise injury in the past was associated with earplug use.^32,39 In this study, eligible participants who intended to use earplugs were excluded. Therefore, we cannot draw conclusions on the effect of a previous noise injury on the intention to use earplugs from our study data. When assigned to the earplug group, participants were asked to use the earplugs for the entire visit. Only 3 participants who were assigned to the earplug group admitted that they did not use them for the entire festival visit but for most of the festival visit. We expect participants to have given socially desirable answers to questions from the questionnaire; therefore, this number is probably an underestimation. Assuming more participants in the earplug group did not use the earplugs for the entire festival visit, the protective effect of earplugs might be even stronger than the effect that we found in our study.

One limitation of this study is that we used a self-designed questionnaire that was not validated. Recent studies on animal models have shown that noise exposure not leading to permanent threshold shifts cause cochlear synaptopathy.⁴⁰ Cochlear synaptopathy has been described as hidden hearing loss because it is not detectable using standard audiometry. Because no standardized test is available to measure hidden hearing loss,⁴¹ we used standard audiometry in our study to detect a TTS. Therefore, we were not able to detect hidden hearing loss in our study participants. Another limitation of this study is that audiometric data at 3.0 kHz were missing in 12 participants. Using the mean of 2.0- and 4.0-kHz data to replace these missing data might have reduced the possible bias that resulted from these missing data.

These variables explain only part of the variance of the TTS outcomes in our participants. No correlation between time until evaluation and TTS was found, indicating that a (partial) recovery of the TTS before participants underwent evaluation was unlikely. We presume that genetic susceptibility and environmental differences can explain the individual differences in susceptibility to noise that are still unexplained by our model.^7,8,42,43 Furthermore, one might argue that the noise reduction rate of the earplugs may have differed per participant because these rates were not personalized. In addition, the exact level of noise exposure per participant was unknown because localization on the festival terrain was unknown. This variability between participants would contribute to the unexplained variance in the model. Furthermore, our questionnaire did not include a question concerning smoking habits. Previous studies have shown that cigarette smokers are more likely to develop NIHL when exposed to high sound pressure levels.^27-30 In addition, race could not be analyzed in our study owing to too little variance in our data. Literature suggests that white persons are more susceptible to noise than are African American persons.^9-11,44 Analysis of these factors in future research on predictors of recreational NIHL would be of interest.

The present study identified factors associated with NIHL at an outdoor music festival. Nonuse of earplugs was the most important factor, followed by alcohol and drug use during the festival and male sex. Considering these factors, physicians could raise more awareness about the combined risk of attending music festivals without using earplugs while consuming alcohol and/or drugs. Secondarily, we investigated the behavior of music festival attendees. The association between earplug use and time spent near stages and loudspeakers was not strong. Attendees not using earplugs reported significantly worse subjective hearing performance and more tinnitus after the festival visit than did attendees who used earplugs. In the earplug group, the perceived loudness and appreciation of music as well as speech perception were associated with the duration of earplug use.

Accepted for Publication: February 23, 2018.

Corresponding Author: Véronique J. C. Kraaijenga, MD, Department of Otorhinolaryngology–Head and Neck Surgery, University Medical Center Utrecht, PO Box 85500, Heidelberglaan 100, 3584CX Utrecht, the Netherlands (v.j.c.kraaijenga@umcutrecht.nl).

Published Online: April 19, 2018. doi:10.1001/jamaoto.2018.0272

Author Contributions: Dr Kraaijenga had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Kraaijenga, van Munster.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: All authors.

Critical revision of the manuscript for important intellectual content: Kraaijenga, van Zanten.

Statistical analysis: All authors.

Administrative, technical, or material support: Kraaijenga.

Study supervision: van Zanten.

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Additional Contributions: Geerte Ramakers, MD, Guido Cattani, MS, and Wilko Grolman (Department of Otorhinolaryngology-Head and Neck Surgery, University Medical Center Utrecht, and Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, the Netherlands) helped set up the experiment for this study, for which they were not compensated. MTV Soundkeepr provided earplugs; MTV Europe, the use of their studio; and van Boxtel Hoorwinkels and Oticon Medical, the audio boxes and audiometers used for the hearing evaluations. We thank all the people of the research and audiological departments of the University Medical Center Utrecht for their help, and the organization of Valtifest for providing the free tickets to the festival.