Make Listening Safe Loss Due to Exposure to Loud Sounds in WHO Recreational Settings

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Estimation of the risk of developing hearing Make Listening Safe loss due to exposure to loud sounds in WHO recreational settings

The objective of this meta-analysis is to comprehensively assess the existing evidence on the levels of risky exposure to loud sounds among young people who listen to music through personal audio devices or frequently attend entertainment venues, and to provide July 2019 an estimated number of young people who are at risk of developing hearing loss due to unsafe listening practices. The document has been prepared by WHO.

Estimation of the risk of developing hearing loss due to exposure to loud sounds in recreational

settings

Authors Dr Shelly Chadha Dr Ricardo Martinez Dr Kaloyan Kamenov

Contents Introduction ...... 1 Objectives ...... 2 Methodology ...... 2 Systematic literature review ...... 2 Inclusion criteria for studies on exposure to loud sounds through the use of personal audio devices ...... 2 Inclusion criteria for studies on exposure to loud sounds in entertainment venues ...... 3 Meta-analysis ...... 3 Results ...... 4 Exposure to loud music through personal audio devices and systems ...... 5 Exposure to loud music through personal audio devices and systems ...... 6 Estimation of the number of young people at risk of developing hearing loss due to recreational loud sounds ...... 7 WHO response ...... 8 References ...... 9

Introduction

Hearing loss affects millions of people around the world and it is anticipated that unless action is taken the number of people with hearing loss could double from its current level by 2050 (1). One of the key contributors to hearing loss is recreational noise. Studies show that more and more young people are at high risk of hearing loss due to exposure to loud sounds in recreational settings, such as bars, discotheques, clubs or sporting events (2,3). On the other hand, most adolescents and young adults listen to music (over personal audio systems) in a way that puts them at risk of hearing loss (4,5). Such hearing loss is of great concern as it is irreversible, while being preventable through safe listening.

Evidence shows that during their leisure time, people seem to expose themselves to loud levels of sound. A typical listener has the volume at a range between 75-100 dB(A) and individuals who listen to 15 minutes of music at 100 dB(A) using personal music players may be exposed to the same level of loudness as industrial workers exposed to 85 dB(A) in an 8-hour day (6). The sound level of personal devices may range between 75 and 105 dB(A); ear-bud type inserted ear phones produce maximum levels ranging from 88 to 113 dB(A) across different devices (7,8). The maximum sound level of available listening devices currently in the market can reach 78 to 136 dB(A) (9). When it comes to recreational venues, many young people are exposed to high-volume music in discotheques, where mean sound levels range from 104 to 112 dB(A), whereas at pop concerts sound levels can often be even higher (10).

Existing occupational safety standards determine sound levels which, if exceeded, are assumed to be potentially damaging for the hearing of a person. For Europe, these limits are 80 dB(A) for 40 hours per week (56 hours including weekends) (11), whereas for Australia, United Kingdom, and Canada the workplace noise limit is set at 85 dB(A) for 40 hours week (56 hours including weekends) (2). Since the sound pressure levels are measured on a logarithmic scale and adding two sounds of equal pressure levels and duration results in a total pressure that is 3 dB(A) higher than each individual sound pressure level (12), it can be assumed that listening to a music level of 80 dB(A) for 56 hours a week is equal to listening to 89 dB(A) for seven hours per week (13). Therefore, the EU’s Scientific Committee on Emerging and Newly Identified Health Risks states

that listening for 1 hour a day to a sound level of more than 89 dB(A) is potentially damaging (14). If this rule is applied also to the standards available in Australia, UK and Canada, then listening to a music level of 94 dB(A) for more than one hour a day could be potentially damaging. Given the existing sound limits and the steady increase in the use of personal audio devices by young people as well as the wide exposure to loud sounds in entertainment venues, it is important to estimate the number of people who are at risk of developing hearing loss due to recreational loud sounds.

Objectives

The objective of this literature review and meta-analysis was to comprehensively assess the existing evidence on the levels of risky exposure to loud sounds among young people who listen to music through personal audio devices or frequently attend entertainment venues, and to provide an estimated number of young people who are at risk of developing hearing loss due to unsafe listening practices.

Methodology

Systematic literature review

Firstly, a literature review was carried out to identify published studies that explore 1) exposure of young people to loud sounds through listening to personal audio devices defined as a risk for developing hearing loss and 2) attendance of people to entertainment venues such as bars of clubs with a frequency defined as a risk for developing hearing loss.

Inclusion criteria for studies on exposure to loud sounds through the use of personal audio devices

• Studies with data gathered between 2003 (year of explosion of mp3 players sales) and 2014.

• Age of participants from 12 to 34 years. This age group was selected as primary users of listening devices • Cross-sectional and retrospective case studies • Exposure to personal listening devices with a frequency defined as a risk of hearing loss by the author of the study. When the frequency was not explicitly defined, Henderson et al. (15) criteria of listening to a device using headphones at least 3 times a week or 3 hours a week defined as risky behavior was used. • No language restrictions were applied.

Inclusion criteria for studies on exposure to loud sounds in entertainment venues

• Studies published from 2000 to 2014 • Age of participants from 12 to 34 years. • Cross-sectional and retrospective case studies • Attendance to entertainment venues such as clubs or discotheques with a frequency defined as a risk of hearing loss by the author of the study. If frequency was not defined, attendance more often than once a month was applied as risky behavior (15). • No language restrictions were applied

In addition, studies investigating exposure to loud sounds in arenas and sports events were included in the search.

Meta-analysis Meta-analysis was carried out with the included studies to estimate the percentage of people who were exposed to unsafe levels of sound through personal audio devices or entertainment venues. Analysis was conducted with MetaXL v2 software as an add-in to Excel, and Comprehensive Meta- Analysis (CMA 3.3). Heterogeneity was measured with Cochrane Q and I2 statistics. Due to the expected significant heterogeneity between studies in terms of different study groups and outcome measures, a random effects model was chosen for the meta-analysis. In a random-effects meta-analysis, it is assumed that each study is estimating a study-specific true effect. The 3

observed heterogeneity in the estimates is normally attributed to two sources - between-study heterogeneity in true effects, and within-study sampling error.

Subgroup analyses by age category, region and country income level were undertaken to see whether the percentage of exposure varied in different subgroups. In the case of income groups, two categories of income were applied - more or equal than $35,000 GNI per capita (named High Income), and less than $35,000 GNI per capita (named Middle-High Income). Sensitivity analyses were also carried out to identify potential outliers among the studies.

Results

Initially, 25 studies were identified as meeting the inclusion criteria. However, due to heterogeneous methodologies, only 15 could be included in the meta-analyses. Nine studies were included in the meta-analysis on exposure to loud sounds through personal audio devices and 11 in the meta-analysis on exposure to loud sounds in recreational settings. All studies were carried out in high- or middle-income countries. Very few studies were found on exposure to loud sounds in arenas and sports events; therefore, performing meta-analysis was not possible. Table 1 shows characteristics of the included studies.

Table 1. Characteristics of the included studies SAMPLE COUNTRY YEAR AUTHORS AGE SIZE UK 2000 Smith PA et al. (2) 356 18-25 Sweden 2004 Olsen W et al. (16) 1285 13-19 USA 2005 Chung JH et al. (3) 3310 13-34 Finland 2005 Jokitulppo J et al. (17) 1054 19-27 Korea 2009 Kim MG et al. (18) 490 13-18 Brazil 2009 Zocoli Am et al. (4) 245 14-18

Netherlands 2010 Vogel I et al. (8) 1512 12-19

USA 2011 Henderson E et al. (19) 2288 12-19

Belgium 2012 Gilles A et al. (11) 145 19-26 Israel 2012 Muchnik C et al. (20) 289 13-16 Netherlands 2012 Vogel I et al. (12) 944 15-25 Taiwan 2013 Tung CH et al. (21) 1787 18.9 * Australia 2013 Beach EF et al. (5) 1000 18-35 Argentina 2014 Serra MR et al. (22) 172 14-15 USA 2013 Le Prell CG et al. (23) 87 18-31 *mean age

Exposure to loud music through personal audio devices and systems

The overall exposure to loud sounds by listening to music through headphones among teenagers and young people (12-34 years) is 48.97% (95% CI 40.28%, 57.70%). Initially, the study by Oghu et al., 2012 (24) carried out in Nigeria was included in the analysis and the overall prevalence was slightly higher – 52.3%, but after applying a sensitivity analysis the study was considered an outlier and excluded. Subgroup analyses by age category and regions were not meaningful due to the scarcity of data. Subgroup analysis by country income, however, was possible and carried out. The results show that the prevalence of exposure to loud sounds through listening to personal audio devices in high-income countries is significantly lower compared to middle-income countries – 33% vs. 61%, respectively. Figure 1 shows the results of the meta-analysis.

Figure 1. Meta-analysis of studies on exposure to loud music through use of audio devices

PLD Random effects by Level of Income Study or Subgroup Prev (95% CI) % Weight High Income 2010_Vogel 0.32 ( 0.30, 0.35) 11.49 2011_Henderson 0.35 ( 0.33, 0.37) 11.53 2012_Vogel 0.30 ( 0.27, 0.33) 11.44 2014_Prell 0.41 ( 0.31, 0.51) 9.94

High Income subgroup 0.33 ( 0.30, 0.36) 44.40 Q=8.96, p=0.03, I2=67%

Middle-High Income 2009_Kim 0.61 ( 0.56, 0.65) 11.27 2009_Maria 0.71 ( 0.65, 0.77) 11.04 2012_Muchnik 0.69 ( 0.64, 0.74) 11.10 2013_Tung 0.46 ( 0.43, 0.48) 11.50 2014_Serra 0.58 ( 0.50, 0.65) 10.69

Middle-High Income subgroup 0.61 ( 0.49, 0.72) 55.60 Q=124.73, p=0.00, I2=97%

Overall 0.49 ( 0.40, 0.58) 100.00 Q=471.00, p=0.00, I2=98%

0.3 0.4 0.5 0.6 0.7 Prev

Exposure to loud music through personal audio devices and systems

The overall exposure to loud sounds due to frequent attendance of entertainment venues among teenagers and young people (12-34 years) is 41.46% (95% CI 26.68% - 57.73%). Data allowed the performance of a subgroup analysis by region, more specifically – dividing the studies carried out in Europe and other regions. Results showed no difference in the estimates – 42% vs 41%, respectively. Sensitivity analysis revealed that the study by Jokitulppo et al., 2005 (17) can be considered as an outlier. After removing it from the analysis, the estimate for the European region drops to 34.1%. Figure 2 shows the results of the meta-analysis.

Figure 2. Meta-analysis of studies on exposure of loud sounds due to attendance of recreational venues

Forest Plot - Disco / Clubs Random effects Disco/clubs Random effects by Region Study or Subgroup Prev (95% CI) % Weight Europe 2000_Smith 0.11 ( 0.08, 0.15) 9.14 2004_Widen 0.35 ( 0.32, 0.38) 9.15 2005_Jokitulppo 0.83 ( 0.81, 0.85) 9.16 2010_Vogel 0.40 ( 0.38, 0.43) 9.16 2012_Gilles 0.37 ( 0.29, 0.45) 8.96 2012_Vogel 0.48 ( 0.45, 0.51) 9.14

Europe subgroup 0.42 ( 0.21, 0.64) 54.70 Q=1531.73, p=0.00, I2=100%

Other Regions 2005_Chung 0.23 ( 0.22, 0.24) 9.17 2013_Beach 0.14 ( 0.12, 0.16) 9.16 2013_Tung 0.69 ( 0.67, 0.71) 9.16 2014_Serra 0.63 ( 0.56, 0.71) 8.99 2014_Prell 0.41 ( 0.31, 0.51) 8.81

Other Regions subgroup 0.42 ( 0.18, 0.66) 45.30 Q=1715.61, p=0.00, I2=100%

Overall 0.42 ( 0.27, 0.58) 100.00 Q=3603.15, p=0.00, I2=100%

0.2 0.4 0.6 0.8 Prev

Estimation of the number of young people at risk of developing hearing loss due to recreational loud sounds

There is no evidence on the overlap of people who listen to music through personal audio systems and attend entertainment venues frequently. Therefore, both estimates could not be applied together for the estimation of the number of young people at risk of developing hearing loss due to recreational loud sounds. A compromise decision was taken to use the higher prevalence (in this case the 48.97% exposure of young people to loud sounds through personal audio devices) as an indicator of risky behaviour that might lead to hearing loss. When this percentage was applied to the 2015 population of people between 12-34 living in middle- and high-income countries (25),

it was revealed that an estimated 1,14 billion young people were at risk of developing hearing loss due to exposure to loud sounds in recreational settings.

Only population living in high- and middle-income countries was considered as all studies included in the analyses were carried out in middle- and high-income settings. Low-income countries were not considered as the behaviour of young people living in those countries might be different. It has to be noted that the 1.14 billion is an underestimation, since 1) people can risk their hearing through attending entertainment venues frequently without being users of personal audio devices and 2) there are many more people living in low-income settings that are possibly exposed to loud sounds putting their hearing in danger. If actions are not taken, this number will increase significantly in the upcoming decades.

WHO response

WHO is working extensively towards promoting safe listening practices among young people. In collaboration with the International Telecommunications Union, a standard for the manufacture and use of personal audio devices such as smartphones and MP3 players was developed and launched (read more here: https://www.who.int/deafness/make-listening-safe/standard-for-safe- listening/en/ ). The standard offers recommendations on safe listening features to be included in such devices. The implementation of this standard would allow for safe listening. Furthermore, communication campaign for safe listening is undergoing with the aim to raise awareness about safe listening practices especially among young people and highlight the need for safe listening to policy-makers, health professionals, parents and others. Lastly, WHO, in collaboration with partners, is currently developing a regulatory framework for control of exposure to sound in entertainment venues.

References

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