- the first (lower) action level set at LEX,8h = 80 dBA;
- the second (upper) action level set at LEX,8h = 85 dBA; and,
- the maximum exposure limits set at LEX,8h = 87 dBA.
1.1. Leisure Activities
1.2. Aircraft, Road and Rail Noises
1.3. Impulse Noise
2. Materials and Methods
- High quality—Further research is very unlikely to change our confidence in the estimate of effect;
- Moderate quality—Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate;
- Low quality—Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate; and,
- Very low quality—Any estimate of effect is uncertain.
3.1. This Study Selection and Characteristics
3.2. Risk of Bias within Studies
- Feder et al. (2013) —Low participation rate (only 11% of out of 237 invited subjects);
- Sulaiman et al. (2013) —The selection of participants was most likely not random and the response rate was not provided;
- Lévesque et al. (2010) —No inclusion or exclusion criteria were specified. No confounding factors were included. A lack of randomization. The diagnostic criteria of tinnitus were not specified;
- Vogel et al. (2014) —No direct measurement of noise levels; lack of randomization. It is not clear what proportion of subjects with “permanent hearing-related symptoms” experienced permanent tinnitus. No validated method of tinnitus assessment;
- Sulaiman et al. (2014) —No information provided about blinding the health outcome and/or exposure assessment.
3.3. Results of Individual Studies
3.3.1. Permanent Hearing Loss
3.3.2. Permanent Tinnitus
3.4. Synthesis of Results
3.4.1. Permanent Hearing Loss
3.4.2. Permanent Tinnitus
3.4.3. Risk of Bias across Studies
4.1. Summary of Evidence
- While using very strict inclusion criteria, there is low quality GRADE evidence that prolonged listening to loud music through PLDs increases the risk of hearing loss and results in worsening standard frequency audiometric thresholds.
- Specific threshold analyses focused on risk stratification of permanent hearing loss according to clearly defined levels of exposure to music through the PLDs are missing. This is due to many restrictions of conducting such research that are related to the long latency time from exposure to effect, the problems to correctly estimate the exposure, and the lack of sensitive measures to detect early signs of hearing loss.
- Available, yet very limited, data contradict any positive association between prolonged listening to loud music through PLDs and the risk of permanent tinnitus. Future studies are needed to provide actionable guidance for PLDs users.
- No studies fulfilling the inclusion criteria related to other isolated or combined exposures to environmental noise were identified.
- Since measurable audiometric hearing loss requires long exposure periods and individual dosimetry is preferable to overcome the methodological and practical drawbacks in exposure assessment, such cohort studies would be very challenging.
Conflicts of Interest
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|Action Level||LEX,8h||Equivalent Levels for Time Indicated (Trade-Off 3 dB)|
|First Action level (minimum) provide protection||80 dB(A)||83 dBA-4 h *; 86 dBA-2 h; 89 dBA-1 h;|
|92 dBA-30 min **; 95 dBA-15 min; 98 dBA-8 min;|
|101 dBA-4 min; 104 dBA-2 min; 107 dBA-1 min|
|Second Action level mandatory protection||85 dB(A)||88 dBA-4 h; 91 dBA-2 h; 94 dBA-1 h;|
|97 dBA-30 min; 100 dBA-15 min; 105 dBA-5 min;|
|111 dBA-1 min|
|Maximum Exposure limit value||87 dB(A)||90 dBA-4 h; 93 dBA-2 h; 96 dBA-1 h;|
|99 dBA-30 min; 102 dBA-15 min; 107 dBA-5 min;|
|113 dBA-1 min|
|No||Author, Year||Population||Exposure||References Group||Confounding||Outcome|
|1.||Keith et al. (2011) ||248 Canadian individuals aged 10–18, 110 males and 138 females, 29 subjects excluded, random school and student selection.||Individual LEX was calculated according to ISO 1999, open-ended question about the hours per week listening to music, weekly allowable listening duration time was divided by seven to derive an estimate of average daily listening duration, measurement made in classrooms, for 32 s listening of music at the typical and “worst-case” volume levels, background noise between 40 and 52 dBA.||ISO 1990||All uncertainty estimates were based on the ISO/IEC guide (ISO/IEC, 1995).|
Low participation rate of 11%.
|3.2% of subjects were estimated to exceed the level limit of 85 dBA LEX of the typical volume settings. 77.5% of listeners were exposed to the level for which there is no known risk of permanent noise induced hearing loss, i.e., ≤75 dBA LEX.|
|2.||Portnuff et al. (2013) ||52 US individuals, aged 18–29, hearing threshold no worse than 20 dB HL, at least 10 h use of PLD a week, 24 from this group were chosen at random for dosimetry.||An earphone data logging system connected with the dosimeter was developed in order to record the real-world use of PLD, dose calculation: self-reported chosen listening level (CLL) (Dose usual), the CLL by volume control increments (Dose vol) and the measured dose from the logg in system (Dose measured).||NIOSH, OSHA||Bias due to participants selection (listening for at least 10 h a week).||Weekly damage risk criteria were exceeded in 16.7% subjects and 8.3% of subjects according to NIOSH and OSHA standards, respectively.|
|3.||Portnuff et al. (2011) ||29 US individuals (12 males and 17 females), aged 13–17, using MP3 players at least two hours per week, normal hearing thresholds (no worse than 15 dB HL).||Individual noise doses calculated based on self-reported listening time and self-reported volume control setting (based on translation of volume control settings to diffuse-field equivalent output levels).||EPCEU, NIOSH and OSHA criteria||No direct SPL measurement.||Doses of noise higher than damage risk criteria in 0%—OSHA, in 6.9%—NIOSH, 13.8%—EPCEU of subjects.|
|4.||Lee et al. (2014) ||1928 Singapore university freshman, aged 16–21 years, different races, 129 students excluded, 95.8% regular PLD users.||Based on volume setting and questionnaire. Pre-calibrated MP3 players, so the equivalent A-weighted SPL of the different volume settings was known||TWA 8 h > 85 dBA||No direct SPL measurement||16.4% students were exposed at TWA 8 h > 85 dBA. Differences between races—Chinese less exposed.|
|5.||Muchnik et al. (2012) ||74 Israeli individuals (26 males and 48 females), aged 14–16 year, regular PLDs users, no history of hearing problems and middle ear pathologies.||Preferred listening levels of six types of PLDs. Volume control setting transformed to SPLs which were in turn converted to equivalent diffuse field A-weigthed levels, ambient noise 61–70 dBA. LAeq 85 dBA were calculated.||NIOSH||No direct SPL measurement.|
Measurement done in the presence of background noise.
|Mean preferred listening level 89 (SD—9) dBA. 26% of the participants in the noisy condition were found to be at risk according to occupational damage risk NIOSH criteria (NIOSH 1998).|
|6.||Vogel et al. (2011) ||1687 Dutch students from 15 Dutch secondary schools invited, response rate 89.9% (1512 subjecrts, 89.9% of tjose PLD users)||Average weekly exposure time to MP3 players was estimated by referring the volume of the device to dB(A) value and multiplying days per week and hours per day to calculate (weekly) Permissible Exposure Limits (PELweek = music level of 89 dBA listen for 56 h a week).||89 dBA for ≥1 h per day.|
Reffered to the safe level of 80 dBA (like in SCENIHR report) converted to LEX,w of 56 h.
|No direct SPL measurement.||28.6% of risk 89 dBA ≥ 1 h.|
|Source||Leisure Steady-State Noise/Music||Impulse Noise||Aircraft/Traffic Noise and Other Exposures||Total|
|Number of Studies||PLD||Bars||Concerts||Sport Events||Toys, Firearms & Firecrackers|
|Excluded studies||116||15||68||6||37||12||215 *|
|No||Author and Year||Study Design and the Number of Subjects||Age of Subjects (Year)||Exposure Assessment||Health Outcome and the Method of Measurement||The Number (Percent) of Subjects with Hearing Loss/Tinnitus||Data Analysis||Main Results and Conclusions||Risk of Bias|
|1.||Feder et al. (2013) ||Cross-sectional (n = 237)||10–17||Individual Leq(32 s) and LEX,8h estimates||Permanent hearing loss; PTA||Data not reported||Multivariate models for audiometric frequencies (estimate (SE), p-value from t-test based on multivariate model).||Positive correlation between Lex(8 h) and hearing threshold at 4 kHz and LFPTA (low frequency pure-tone average for frequencies 0.5, 1 and 2 kHz)|
Subjects reporting using their player for >5years and those reporting using their player for 1 to <3 years both had higher HT than those using their player for <1 year
|High, due to low subject participation rate (only 11%) and no information provided about blinding the health outcome and/or exposure assessment|
|2.||Sulaiman et al. (2013) ||Cross-sectional (n = 177)||13–16||Individual LAeq8h||1. Permanent hearing loss; standard PTA and extended high frequencies PTA|
2. Tinnitus (possibly permanent)
|Hearing loss found in 13 (7.3%) of subjects in entire population.|
Tinnitus reported by 30 (16.9%) subjects exposed to music at LAeq8h ≤ 75 dBA and by 7 (4.0%) of those exposed to music at LAeq8h >75 dBA.
|Pearson correlation test, Chi-squared test||No significant association between subjects’ LAeq8h exposure levels and the incidence of hearing loss (defined as HT ≥ 25 dB at one or more standard frequencies), or the occurrence of notched audiograms.|
Weak significant correlation between individual LAeq8h and HT at 11.2 and 14 kHz.
No relationship between individual LAeq8h and tinnitus.
|High, the response rate was not provided, neither the information about blinding the health outcome and/or exposure assessment.|
|3.||Sulaiman et al. (2014) ||Cross-sectional (35 exposed subjects and equal number of age and sex matched not exposed subjects)||18–30||Individual LAeq8h||Permanent hearing loss; standard PTA and extended high frequencies PTA, otoacoustic emissions||Hearing loss (defined as HT ≥ 25 dB at one or more standard frequencies) in 12 (34.3%) of users and 4 (11.4%) of control subjects.||Descriptive analysis, unpaired Student t test, Pearson correlation test, Fisher’s exact test.||Significant association between the incidence of hearing loss and PLDs usage.|
Weak but significant correlation between users’ LAeq8h exposure levels and their PTA thresholds pooled from 3, 4 and 6 kHz in the right ear only.
Hearing thresholds of PLDs users at extended high frequencies significantly higher than in non-users.
Otoacoustic emissions amplitudes in users significantly reduced compared with controls.
|High, no information provided about blinding the health outcome and/or exposure assessment.|
|4.||Lévesque et al. (2010) ||Cross-sectional (n = 124)||14–17||Individual LAeq8h||Tinnitus (possibly permanent); questionnaire||Tinnitus reported by 2 (4.1%) of subjects exposed to music at LAeq8h ≤ 80 dBA and by 12 (16.0%) of those exposed to music at LAeq8h > 80 dBA.|
Tinnitus reported by 5 (6.9%) of subjects exposed to music at LAeq8h ≤ 85 dBA and by 9 (17.3%) of those exposed to music at LAeq8h > 85 dBA.
|Binary outcome, chi2 test||Significant difference in prevalence of tinnitus between groups when the LAeq8h reference value set at 80 dBA.|
No significant difference in prevalence of tinnitus when the LAeq8h reference value set at 85 dBA.
|Very high, due to the lack of specification of inclusion/exclusion criteria, participation rate 63.3%, diagnostic criteria of tinnitus not specified, no confounding factors included, no information provided about blinding the health outcome and/or exposure assessment.|
|5.||Vogel et al. (2014) ||Cross-sectional (n = 943)||16–25||Individual sound levels in dBA for 56 h per week, estimated based on PLD volume setting (Permissible Exposure Limits (PELweek = music level of 89 dBA listen for 56 h a week)||Permanent hearing-related symptoms; questionnaire (not clear what proportion of subjects with “permanent hearing-related symptoms” experienced permanent tinnitus)||Permanent hearing-related symptoms reported by 101 (10.7%) of subjects not at risk (<80 dBA), 93 (9.9%) of subjects at low risk (80–85 dBA), 97 (10.3%) of subjects at moderate risk (85–90 dBA) and 41 (4.4%) of subjects at high risk (≥90 dBA).||Multiple logistic regression; ORs: 0.86 (0.49–1.46), 0.93 (0.50–1.75) 0.39 (0.18–0.86) for low risk (80–85 dBA), moderate risk (85–90 dBA) and high risk (≥90 dBA) group of listeners.||Students not experiencing permanent hearing-related symptoms listen > 2.5 times more often to high-risk sound levels (equivalent to ≥ 90 dBA for 56 h per week).||High, because of the lack of direct measurement of sound pressure levels, health outcome assessment leading to information bias.|
|No||Author and Year||Health Outcome||Reference Values (LAeq8h)||OR||(95% CI)||Number of Participants||Risk of Bias|
|1.||Sulaiman et al. (2013) ||Tinnitus||≤75 dBA||1.00||177||High|
|>75 dBA||1.13 1||(0.44—2.89) 1|
|2.||Levesque et al. (2010) ||Tinnitus||≤80 dBA||1.00||124||Very high|
|>80 dBA||4.48 1||(0.94–21.29) 1|
|>85 dBA||2.80 1||(0.87–9.04) 1|
|3.||Vogel et al. (2014) ||Permanent hearing related symptoms (tinnitus)||<80 dBA||1.00||943||High|
|4.||Sulaiman et al. (2014) ||Permanent hearing loss *||non users||1.00||70||High|
|Users **||4.04 1||(1.13–14.49) 1|
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