Cochrane method for systematic review and meta-analysis of interventions to prevent occupational noise-induced hearing loss – abridged

Revisão sistemática e metanálise Cochrane de intervenções para prevenção de perda auditiva ocupacional induzida por ruído – abreviada

ABSTRACT

Purpose

Assess the effect of non-pharmaceutical interventions at work on noise exposure or occupational hearing loss compared to no or alternative interventions.

Research strategies

Pubmed, Embase, Web of Science, OSHupdate, Cochrane Central and Cumulative Index to Nursing and Allied Health Literature (CINAHL) were searched.

Selection criteria

Randomized Controlled Trials (RCT), Controlled Before-After studies (CBA) and Interrupted Time-Series studies (ITS) evaluating engineering controls, administrative controls, personal hearing protection devices, and hearing surveillance were included. Case studies of engineering controls were collected.

Data analysis

Cochrane methods for systematic reviews, including meta-analysis, were followed.

Results

29 studies were included. Stricter legislation can reduce noise levels by 4.5 dB(A) (very low-quality evidence). Engineering controls can immediately reduce noise (107 cases). Eleven RCTs and CBA studies (3725 participants) were evaluated through Hearing Protection Devices (HPDs). Training of earplug insertion reduces noise exposure at short term follow-up (moderate quality evidence). Earmuffs might perform better than earplugs in high noise levels but worse in low noise levels (very low-quality evidence). HPDs might reduce hearing loss at very long-term follow-up (very low-quality evidence). Seventeen studies (84028 participants) evaluated hearing loss prevention programs. Better use of HPDs might reduce hearing loss but other components not (very low-quality evidence).

Conclusion

Hearing loss prevention and interventions modestly reduce noise exposure and hearing loss. Better quality studies and better implementation of noise control measures and HPDs is needed.

Keywords:
Noise-Induced Hearing Loss; Occupational Noise; Hearing Protective Devices; Systematic Review; Meta-Analysis

RESUMO

Objetivo

Avaliar o efeito de intervenções no trabalho sobre a exposição ao ruído ou a perda auditiva em comparação com ausência ou intervenções alternativas.

Estratégia de pesquisa

Buscas em Pubmed, Embase, Web of Science, OSHupdate, Cochrane Central e CINAHL.

Critérios de seleção

Incluídos ensaios clínicos randomizados (ECR), estudos controlados pré/pós-intervenção (ECPPI) e estudos de séries temporais interrompidas (SIT) avaliando controles de engenharia, administrativos, equipamentos de proteção auditiva (EPAs) e vigilância auditiva. Coletados estudos de caso de engenharia.

Análise dos dados

Cochrane para revisões sistemáticas, incluindo metanálise.

Resultados

Foram incluídos 29 estudos. Legislação mais rigorosa pode reduzir níveis de ruído em 4,5 dB(A) (evidência de qualidade muito baixa). Controles de engenharia podem reduzir imediatamente o ruído (107 casos). Onze ECR e ECPPI (3.725 participantes) avaliaram EPAs. Treinamento para inserção do EPA reduz a exposição ao ruído no acompanhamento de curto prazo (evidência de qualidade moderada). Protetores tipo concha podem ter desempenho melhor do que protetores de inserção em níveis altos de ruído, mas piores em níveis mais baixos (evidência de qualidade muito baixa). EPAs podem reduzir a perda auditiva no acompanhamento de muito longo prazo (evidência de qualidade muito baixa). Dezessete estudos (84.028 participantes) avaliaram programas de prevenção de perdas auditivas. Um melhor uso do EPA pode reduzir a perda auditiva, mas outros componentes não (evidência de qualidade muito baixa).

Conclusão

As intervenções para prevenção da perda auditiva reduzem modestamente a exposição ao ruído e a perda auditiva. Estudos de melhor qualidade e melhor implementação de medidas de controle de ruído e EPA são necessários.

Descritores:
Perda Auditiva Provocada por Ruído; Ruído Ocupacional; Dispositivos de Proteção Auditiva; Revisão Sistemática; Metanálise

INTRODUCTION

Worldwide millions of workers are exposed to noise levels that increase their risk of hearing disorders⁽¹⁾. While hearing loss prevention programs (HLPPs) are mandatory in many countries, the reportedly continuing high rate of occupational noise-induced hearing loss (NIHL) casts doubt upon their effectiveness⁽²⁾. Moreover, the broad range of interventions included in HLPPs makes it difficult to appraise the most effective strategy. A systematic review of studies that evaluated interventions to reduce occupational exposure to noise or to decrease occupationally induced hearing loss is therefore warranted. This paper summarizes the main results of the second update of the Cochrane review originally published in 2009.

Purpose

To assess the effectiveness of non-pharmaceutical interventions for preventing occupational noise exposure or occupational hearing loss compared to no or alternative interventions.

Research strategy

This is an abridged version of the second update of a Cochrane Review originally published in 2009 based on the methods originally described in the review protocol⁽³⁾. Systematic searches were conducted combining search words for the occupational setting, exposure, interventions, and effects on noise or hearing loss. No restrictions on language were used, publication year or publication status and were searched Pubmed, Embase, Web of Science, OSHupdate, Cochrane Central and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases up until September 2016 (search history in ^{Appendix 1} and ^{Appendix 2}). To determine which studies fulfilled the inclusion criteria, pairs of the review authors independently scanned the titles and abstracts of every record retrieved from the databases. Full articles were retrieved for further eligibility assessment.

Data were independently extracted for each included study and resolved discrepancies by discussion. A standard form to extract information about was used: study design, randomisation methods, setting, participants, interventions, outcome measures, follow-up, and adverse events. To assess whether HLPPs are as good as not being exposed, it had to be made an assumption about the minimal clinically relevant hearing loss. Hearing loss was associated with exposure to 85 dB(A) as the minimum amount of damage that should be avoided by the interventions. Based on International Organization for Standardization (ISO) 1990⁽⁴⁾, the amount of hearing loss after five years of exposure to 85 dB(A) was calculated for the median, 10th and 90th percentile would be 4.2 dB, 2.1 dB and 6.1 dB, respectively. This is equivalent to a mean of 4.2 dB hearing loss and represents clinically relevant hearing loss⁽⁵⁾. This means, the 95% CI from meta-analysis results on hearing loss can include zero, but not 4.2 to assure

that the protected and non-exposed groups are equivalent⁽⁶⁾.

Selection criteria

We included studies that 1) used a randomised controlled, controlled before-after, or interrupted time-series study design, 2) included workers exposed to noise levels greater than 80 dB(A), 3) concerned interventions aimed at reduction of noise exposure to prevent NIHL, and 4) used noise exposure or NIHL as an outcome. Case studies on the effects of engineering control interventions without a control group could be included. The results of case studies for the conclusions of the review, as the study design did not fulfil our inclusion criteria, were not used.

Data analysis

Eight authors of recent studies were contacted regarding missing or unclear information and were obtained additional data from three^(7-9).

When authors reported results separately for participant groups^(10,11) we combined these following the Cochrane Handbook for Systematic Reviews of Interventions guidance⁽¹²⁾. In two studies, multiple interventions were compared with one control group. To avoid using the same control group data more than once, the control group was split into three⁽¹³⁾ or two⁽¹⁴⁾ equal subgroups that were subsequently combined in the meta-analysis.

To evaluate the risk of bias, the quality criteria presented by Ramsay et al.⁽¹⁵⁾ for ITS studies was used. For RCTs and cohort studies, the internal validity items by Downs and Black⁽¹⁶⁾ were used that are mostly congruent with the Cochrane 'Risk of bias' tool⁽¹⁷⁾. We defined studies’ overall risk of bias as low if they scored more than 50% of the maximum score.

Sufficiently homogeneous studies, regarding interventions, participants, settings and outcomes in a meta-analysis, were combined. When results were statistically heterogeneous according to the I² statistic, a random-effects model for the meta-analysis was used. A sensitivity analysis to assess the influence of risk of bias on the pooled effect sizes was conducted.

We deemed change in hearing level at 4 kHz and Standard Threshold Shifts (STS) as similar outcome measures for hearing effects and calculated Standardized Mean Differences (SMD) to enable combination of both measures in the meta-analysis⁽¹⁸⁾. For easing interpretation, we transformed the pooled SMDs back to a mean change in hearing level in dB using the median standard deviation of the included studies.

The Grading of Recommendation, Assessment, Development and Evaluation (GRADE) approach to rate the quality of the evidence for each outcome was followed. The grading is based on study design, risk of bias, consistency, directness (generalisability), precision and publication bias across all studies⁽¹⁹⁾. Overall quality is considered high for RCTs and low for observational studies and can be further reduced or upgraded⁽²⁰⁾ (Table 1).

Table 1
Assessment of quality of evidence (GRADE)

Comparison	N Studies	1. RoB?	2. Inconsistent?	3. Indirect?	4. Imprecise?	5. Pub bias?	6. Large ES?	7. DR?	8. Opp Conf	Quality a
Outcome noise
Legislation vs no legislation	1 ITS	yes	1 study	no	no	1 study	yes	no	no	very low(1)
One HPD vs another HPD	1 RCT 4 CBA	2 yes	no	no	no	not shown	no	no	no	low(1)
HPD+Instruction vs HPD-instruction	2 RCT	2 no	no	no	yes	not shown	na	na	na	moderate(7)
Information vs no information	1 RCT (2 arms)	1 yes	1 study	no	yes	1 study	na	na	na	low(1,7)
Outcome hearing loss
One HPD vs another HPD (TTS)	2 CBA									no data
Earmuffs vs Earplugs	2 CBA	2 yes	no	no	yes	not shown	no	no	no	very low(1,7)
Frequent HPD vs less frequent use	1 CBA	1 yes	1 study	no	yes	1 study	no	no	no	very low(1)
HLPP vs audiometry	1 RCT	1 yes	1 study	no	no	1 study	na	na	na	moderate(1)
HLPP+exposure information vs HLPP-information	1 CBA	1 yes	1 study	no	yes	1 study	no	no	no	very low(1,7)
Frequent HPD in HLPP vs less	5 CBA	5 yes	no	no	yes	not shown	no	no	no	very low(1,7)
HLPP vs no exposure	7 CBA	7 yes	no	no	yes	not shown	no	no	no	very low(1,7)
Follow-up vs no follow-up	1 CBA	1 yes	1 study	no	yes	1 study	no	no	no	very low(1,7)
HLPP+long shifts vs HLPP normal	1 CBA	1 yes	1 study	no	yes	1 study	no	no	no	very low(1,7)

• 1-5 Reasons for downgrading: 1. Risk of bias/Limitations in study design; 2. Inconsistency between studies; 3. Indirectness of PICO; 4. Imprecision of the results; 5. Publication bias; 6-8 Reasons for upgrading: 6. Large effect size. 7. Dose-response relationship 8. Confounding opposes the direction of the effect
• ^a
  Final grading of quality of evidence, between brackets domain that led to down/upgrading the quality
• Caption: N = number of; ITS = interrupted timeseries analysis; RCT = randomized controlled trial; CBA = controlled before after study; na= not applicable; 1 study = only one study available and impossible to assess consistency or publication bias

Ratings are interpreted as: 1) high-quality evidence is unlikely to change, moderate-quality evidence; 2) further research is likely to have an impact and may change estimates, low-quality evidence; 3) further research is very likely to have an important impact, and very low-quality evidence provides very uncertain effects estimates.

The results for the most important comparisons in 'Summary of Findings' (SoF) were presented tables.

RESULTS

29 studies (Figure 1, Table 2, ^{Appendix 1}, ^{Appendix 2})^{(7-11,13,14,21-42)} were included. One study evaluated legislation to reduce noise exposure in a 12-year ITS analysis. Thirteen studies with 3725 participants evaluated effects of personal HPDs (three RCTs and ten CBAs). Fifteen studies with 84,028 participants evaluated effects of HLPPs (two RCTs and thirteen CBAs).

Figure 1
Study flow diagram

Table 2
Overview of study characteristics

Study ID	Design	Participants	Intervention	Outcomes	Follow-up
Forouzanfar et al. (2016)(1) and Adera (1993)(21)	CBA	Various occupations, Military, USA	HLPP	HL	Long-term
Adera et al. (2000)(11)	CBA	Various occupations, n = 19,640, 1 company, USA	HLPP	HL	Long-term
Berg et al. (2009)(22)	RCT	Agricultural students involved in farm work, n = 753, 34 schools, USA	HLPP	HL	Long-term
Brink et al. (2002)(23)	CBA	Automobile workers, n = 264, 1 company, USA	HPD	HL	Long-term
Davies et al. (2008)(7)	CBA	Lumber mills workers, n = 22,376, Canada, British Columbia	HLPP	HL	Long-term
Erlandsson et al. (1980)(24)	CBA	Shipyard workers, n = 40, 1 shipyard, Sweden	HPD	HL	Long-term
Gosztonyi (1975)(25)	CBA	Various occupations in 1 company, n = 142, USA	HLPP	HL	Long-term
Hager et al. (1982)(26)	CBA	Various workers, n = 43, 1 company, USA	HLPP	HL	Long-term
Heyer et al. (2011)(27)	CBA	Workers, n = 6483, 2 automotive plants, 1 food-processing plant, USA	HLPP	HL	Long-term
Horie (2002)(28)	CBA	Steel industry quality check workers, n = 12, 1 company, Japan	HPD	HL	Immediate
Huttunen et al. (2011)(29)	CBA	Orchestra, n = 10, Finland	HPD	NE	Immediate
Joy and Middendorf (2007)(8)	ITS	Coal mines, Workplace measurements n = 142,735 Whole mining branch, USA	Legislation	NE	Long-term
Lee-Feldstein (1993)(30)	CBA	Automobile workers, n = 11,435, 1 company, USA	HLPP	HL	Long-term
Meyer and Wirth (1993)(31)	CBA	Various occupations, n = 1377, Military, USA	HLPP	HL	Long-term
Moshammer et al. 2015(32)	CBA	Fitters and welders, n = 125, steel factory, Austria	HPD	HL	Immediate
Muhr et al. (2006)(13)	CBA	Army conscripts, n = 885, Military, Sweden	HPD	HL	Short term
Muhr et al. (2016)(33)	CBA	Army conscripts, n= 1234, Military, Sweden	HLPP	HL	Short term
Nilsson (1980)(34)	CBA	Ship builders, n = 231, Sweden, 1 shipyard	HPD	HL	Long-term
Pääkkönen et al. (1998)(35)	CBA	Shooter, n=5, Military, Finland	HPD	NE	Immediate
Pääkkönen et al. (2001)(36)	CBA	Air combat plane, n = 2, Military, Finland	HPD	NE	Immediate
Park and Casali (1991) instruction(37)	RCT	Various workers, n = 40, several companies, USA	HPD	HL	Immediate
Park and Casali (1991) protection(37)	RCT	Various workers, n = 40, several companies, USA	HPD	HL	Immediate
Pell (1973)(10)	CBA	Various workers, n = 1572, 1 company, USA	HLPP	HL	Long-term
Rabinowitz et al. 2011(9)	CBA /ITS	Various workers of an aluminium smelter, n = 312	HLPP	NE, HL	Long-term
Reynolds et al. (1990)(38)	CBA	Workers, n = 852, 1 company in the chemical industry, USA	HLPP	HL	Long-term
Royster (1980)(39)	CBA	Workers, n = 70, various occupations, USA	HPD	HL	Immediate
Salmani et al. (2014)(40)	RCT	Workers, n = 150, Iran	HPD	NE	Immediate
Seixas et al. (2011)(14)	RCT	Construction workers, n = 176, USA	HPD	NE	Short term
Simpson et al. (1994)(41)	CBA	Various occupations, n = 13283, 21 companies, USA	HLPP	HL	Long-term

• Caption: CBA = controlled before after study, ITS = interrupted time series analysis, RCT = randomised controlled trial, HL = hearing loss, NE = noise exposure, HPD = hearing protection device, HLPP = hearing loss prevention program; n = number

While the participants in all studies were described as being exposed to noise at work, these descriptions were often based on measurement methods that were not clearly described. We assumed that the noise exposure was higher than 80 dB(A).

Noise-exposed participants worked in construction, mining, manufacturing, agriculture, forestry, military, an orchestra, unspecified company or in various workplaces. One study did not describe workplaces⁽⁴⁰⁾.

In most studies, only men were included or there were mostly male workers at the workplaces studied.

Most studies scored poorly on all aspects of the risk of bias checklist (Figure 2) and only six studies scored an overall low risk of bias^{(13,22,28,29,37,40)}.

Figure 2
Risk of bias summary for included studies

The effect of engineering interventions (following legislation) on noise exposure was evaluated in one ITS study. The study⁽⁸⁾ found that new legislation in the mining industry reduced the median personal noise exposure dose in underground coal mining by 27.7 percentage points (95% Confidence Interval (CI) -36.1 to -19.3 percentage points) immediately after the implementation of stricter legislation (Table 3). This roughly translates to a 4.5 dB(A) decrease in noise level. The intervention was associated with a favourable but statistically non-significant downward trend in time of the noise dose of -2.1 percentage points per year (95% CI -4.9 to 0.7, four-year follow-up, very low-quality evidence).

Table 3
SoF table – Stricter legislation (noise exposure)

Stricter legislation compared with existing legislation for noise exposure Patient or population: workers with noise exposure Settings: coal mines Intervention: stricter legislation Comparison: existing legislation
Outcomes	Illustrative comparative risks* (95% CI)		No of observations (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Existing legislation	Stricter legislation
Immediate change in level in year 2000 (noise level at work as PEL dose in dB(A); range 0 to 6400, log scale) 1 year	The mean noise levels during pre-intervention years were 56.9 PEL dose	The mean noise exposure level after introduction was 27.70 PEL dose lower (36.1 lower to 19.3 lower PEL dose)	14 years pre-intervention and 4-years post-intervention (1 ITS)	very low1	The reduction of 27.7 PEL dose translates to about 4.5 dB(A)
Change in slope after introduction (noise level at work as PEL dose in dB(A); range 0 to 6400, log scale) 4 years	The mean noise levels during pre-intervention years were 56.9 PEL dose	The mean change in level of noise exposure per year after introduction was 2.10 PEL dose lower (4.90 lower to 0.70 PEL dose higher)	14 years pre-intervention and 4 years post-intervention (1 ITS)	very low 1

• GRADE Working Group grades of evidence. High quality: we are very confident that the true effect lies close to that of the estimate of the effect; Moderate quality: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of effect, but there is a possibility that it is substantially different; Low quality: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect; Very low quality: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect
• ^*
  The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the absolute effect of the intervention (and its 95% CI)
• ¹
  We downgraded by one level from low to very low because there is only one study and it has a high risk of bias
• Caption: CI: Confidence interval; PEL: permissible exposure level; ITS: interrupted time series analysis

Additionally, 12 case studies were collected reporting on 107 uncontrolled studies of engineering control interventions^(43-54). In most cases⁽⁴¹⁾, authors evaluated design changes, followed by installing damping material and silencers⁽²¹⁾, purchasing new equipment⁽¹⁷⁾, using enclosures⁽¹⁵⁾, installing acoustic panels and curtains⁽¹³⁾, and maintenance only⁽⁷⁾. Types of jobs, when reported, included operating machines and driving vehicles. The effect of the intervention was measured as change in absolute noise levels in 87 of the 107 cases and as personal noise exposure for workers in 27 cases.

Studies showed immediate reductions in noise levels of machinery ranging from 11.1 to 19.7 dB(A) as a result of purchasing new equipment, segregating noise sources or installing panels or curtains around sources. However, studies lacked long-term follow-up, a control group, and in some cases the outcome was evaluated by an acoustical consultant or an employee at the firm where the intervention was evaluated and a conflict of interest was apparent (14 cases).

The review found no effects for administrative controls on environmental noise exposure. On-site training sessions giving instructions for HPD use and noise control techniques (sound barriers and distance) did not have an effect on personal environmental noise-exposure levels compared to information only in one cluster-RCT after four months' follow-up (Mean Difference (MD) 0.14 dB; 95% CI -2.66 to 2.38). Another arm of the same study found that personal noise exposure information had no effect on noise levels (MD 0.30 dB(A), 95% CI -2.31 to 2.91) compared to no such information (176 participants, low-quality evidence) (Table 4).

Table 4
SoF table – Training plus exposure information versus training (noise exposure)

Exposure information compared with training as usual for noise exposure
Patient or population: workers exposed to noise Settings: construction industry Intervention: provision of noise level indicator Comparison: safety training as usual
Outcomes	Illustrative comparative risks* (95% CI)		No of participants (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Training as usual	Plus noise level indicator
Change in noise levels at 4 months' follow-up (dB(A))	The mean noise level in the control group ranged from 87.1 to 89 dB(A)	The mean noise level in the intervention groups was 0.3 dB(A) higher (2.31 dB(A) lower to 2.91 dB(A) higher	176 (1 RCT)	low1

• GRADE Working Group grades of evidence. High quality: we are very confident that the true effect lies close to that of the estimate of the effect; Moderate quality: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of effect, but there is a possibility that it is substantially different; Low quality: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect; Very low quality: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect
• ^*
  The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).¹We downgraded by two levels from high to low because of high risk of bias and imprecision
• Caption: CI: Confidence interval; RCT: randomized controlled trial

HPDs reduced noise exposure on average over various frequencies measured by about 20 dB(A) in one RCT and three CBAs (57 participants, low-quality evidence). There was moderate-quality evidence that personal instructions for inserting earplugs into the ear canal have a considerable effect on the noise attenuation of the devices with an 8.6 dB (95% CI 6.9 to 10.3) higher protection averaged across frequencies (two RCTs^(37,40), 140 participants) (Table 5).

Table 5
SoF table – Earplugs with instruction versus no instruction (noise exposure)

Earplugs with instruction compared with no instruction for noise reduction
Patient or population: workers with exposure to noise Settings: industrial Intervention: instruction on how to insert earplugs Comparison: no instruction
Outcomes	Illustrative comparative risks* (95% CI)		No of participants (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Without instruction	With instruction
Mean noise attenuation over 0.5, 1, 2, 3, 4, 6, 8 kHz (dB) Immediate follow-up	The mean noise attenuation ranged across frequencies from 5.5 to 25.9 dB	The mean noise attenuation in the intervention groups was 8.59 dB higher (6.92 dB higher to 10.25 dB higher)	140 participants (2 RCTs)	moderate1

• GRADE Working Group grades of evidence. High quality: we are very confident that the true effect lies close to that of the estimate of the effect; Moderate quality: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of effect, but there is a possibility that it is substantially different; Low quality: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect; Very low quality: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect
• ^*
  The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).¹We downgraded from high quality by one level because of imprecision due to small number of participants
• Caption: CI: Confidence interval; RCT: randomized controlled trial; RCTs: randomized controlled trials

The effects of HPDs on hearing loss were measured in short and long-term follow-up studies. Authors of two studies compared different devices and measured temporary threshold shifts at short-term follow-up but reported insufficient data for analysis. In two CBA studies, the authors found no difference in hearing loss from noise exposure above 89 dB (A) between earmuffs and earplugs at long-term follow-up (Odds Ratio (OR) 0.8, 95% CI 0.63 to 1.03, very low-quality evidence) (Table 6). The long-term evaluation of the effect of earmuffs versus earplugs on hearing loss showed that earmuffs might perform better than earplugs in high noise levels, but worse in low noise levels (very low-quality evidence).

Table 6
SoF table – Earmuffs versus earplugs (hearing loss)

Earmuffs compared with earplugs for noise-induced hearing loss (NIHL)
Patient or population: workers exposed to 88-94 dB(A) Settings: shipyard Intervention: most wearing earmuffs Comparison: most wearing earplugs
Outcomes	Illustrative comparative risks* (95% CI)		Relative effect (95% CI)	No of participants (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Earplugs	Earmuffs
Hearing loss change over 3 years (4 kHz/STS) 2 to 3 years' follow-up	High risk population		OR 0.8 (0.63 to 1.03)	3242 (2 CBA studies)	very low 1	At lower exposures the results were too heterogeneous to be combined
	42 per 1000	34 per 1000 (26 to 43)

• GRADE Working Group grades of evidence. High quality: we are very confident that the true effect lies close to that of the estimate of the effect; Moderate quality: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of effect, but there is a possibility that it is substantially different; Low quality: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect; Very low quality: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect
• ^*
  The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
• ¹
  We downgraded from low quality to very low quality because of high risk of bias in both studies
• Caption: CI: Confidence interval; OR: Odds Ratio; STS: standard threshold shift; CBA: controlled before after study

Authors of another CBA study found that wearing HPDs more often resulted in less hearing loss at very long-term follow-up (very low-quality evidence).

Studies also evaluated the effects of the combination of interventions in a hearing loss prevention programmes on noise exposure and hearing loss. One RCT found no significant effect in lowering noise level with the use of noise level indicators plus basic information or plus intensive information compared to basic information only at two- and four-months follow-up. The noise level decreased 0.32 dB more in the control group at two months (95% CI -2.44, 3.08) but 0.14 dB more in the intervention group at four months (95%CI -2.66 to 2.38). Neither were statistically significant. Also, the comparison of intensive versus basic information showed no significant differences in noise levels at two (-1.7dB, 95% CI -1.24 to 4.64) and four months (0.3 dB, 95% CI -2.31 to 2.91).

One cluster-RCT found no difference in hearing loss at three- or 16-year follow-up between an intensive HLPP for agricultural students and audiometry only (moderate-quality evidence) (Table 7). One CBA study found no reduction of the rate of hearing loss (MD -0.82 dB per year (95% CI -1.86 to 0.22) for a HLPP that provided regular personal noise exposure information compared to a program that did not provide such information (Table 8).

Table 7
SoF table - HLPP versus audiometry (hearing loss)

Hearing loss prevention programme (HLPP) compared to audiometric testing
Patient or population: agricultural students without hearing loss Settings: agricultural schools Intervention: HLPP with information Comparison: audiometric testing only
Outcomes	Illustrative comparative risks* (95% CI)		Relative effect (95% CI)	No of participants (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Audiometric testing only	HLPP with information
Hearing loss STS ≥ 10 dB loss average over 2, 3, 4 kHz in either ear Follow-up: mean three years	21 per 1000	18 per 1000 (6 to 49)	OR 0.85 (0.29 to 2.44)	687 (1 study, RCT)	moderate 1
Hearing loss STS ≥ 10 dB hearing loss average over 2, 3, 4 kHz in either ear Follow-up: mean 16 years	149 per 1000	141 per 1000 (74 to 250)	OR 0.94 (0.46 to 1.91)	355 (1 study, RCT)	moderate 1

• GRADE Working Group grades of evidence. High quality: we are very confident that the true effect lies close to that of the estimate of the effect; Moderate quality: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of effect, but there is a possibility that it is substantially different; Low quality: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect; Very low quality: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect
• ^*
  The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
• ¹
  We downgraded one level from high to moderate due to lack of information on randomisation and allocation concealment
• Caption: CI: Confidence interval; HLPP; hearing loss prevention programme; OR: Odds ratio; STS: standard threshold shift; RCT: randomized controlled trial

Table 8
SoF table - HLPP with exposure information versus HLPP without (hearing loss)

HLPP with exposure information compared with HLPP without exposure information for noise-induced hearing loss (NIHL)
Patient or population: workers exposed to noise Settings: aluminium smelter Intervention: exposure information as part of HLPP Comparison: no such information
Outcomes	Illustrative comparative risks* (95% CI)		No of participants (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Without exposure info	With exposure info
Annual increase in hearing threshold (dB/year at 2,3 and 4 kHz) 4-year follow-up	The mean hearing loss rate in the control group was 1.0 dB per year	The mean hearing loss rate in the intervention groups was 0.82 dB/year lower (1.86 lower to 0.22 higher)	312 (1 CBA study)	very low 1	Matched for age, gender, baseline hearing loss and baseline hearing

• GRADE Working Group grades of evidence. High quality: we are very confident that the true effect lies close to that of the estimate of the effect; Moderate quality: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of effect, but there is a possibility that it is substantially different; Low quality: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect; Very low quality: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect
• ^*
  The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
• ¹
  We downgraded by one level from low to very low because of high risk of bias
• Caption: CI: Confidence interval; HLPP: hearing loss prevention programme; CBA: controlled before after study

There was very low-quality evidence in four long-term studies, that better use of HPDs as part of a HLPP decreased the risk of hearing loss compared to less well used HPDs in HLPPs (OR 0.40, 95% CI 0.23 to 0.69) (Table 9).This could not be shown for worker training, audiometry alone or noise monitoring by very low- and moderate-quality evidences. More individualized information on daily noise exposure as part of a HLPP showed favourable but non-significant effects on hearing loss in one study.

Table 9
SoF table - Better implemented versus less well-implemented HLPP (hearing loss)

Well-implemented hearing loss prevention programme (HLPP) compared to less well-implemented HLPP for hearing loss
Patient or population: workers Settings: exposure to noise Intervention: well-implemented HLPP Comparison: less well-implemented HLPP
Outcomes	Illustrative comparative risks* (95% CI)		Relative effect (95% CI)	No of participants (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Less well-implemented HLPP	Well-implemented HLPP
Hearing loss STS > 10 dB change average over 2, 3 and 4 kHz1; Follow-up: mean 9.3 years	86 per 1000	36 per 1000 (21 to 61)2	OR 0.40 (0.23 to 0.69)3	16,301 (3 studies4)	very low 5	SMD 0.26 (0.14 to 0.47)

• GRADE Working Group grades of evidence. High quality: we are very confident that the true effect lies close to that of the estimate of the effect; Moderate quality: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of effect, but there is a possibility that it is substantially different; Low quality: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect; Very low quality: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect
• ^*
  The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
• ¹
  STS used in two studies, change of mean 4 kHz threshold in one study;
• ²
  Number of events based on median event rate in included studies;
• ³
  Result from the meta-analysis of three studies;
• ⁴
  One extra study provided similar evidence but could not be combined in the meta-analysis;
• ⁵
  We downgraded by one level from low to very low because of risk of bias due to lack of adjustment for age and hearing loss
• Caption: CI: Confidence interval; HLPP: hearing loss prevention programme; OR: Odds ratio; STS: standard threshold shift; SMD: standardized mean difference

In the meta-analysis of four long-term CBA studies the difference in mean changes in hearing level at 4 kHz was 0.53 dB (95%CI -0.53 to 1.68)^{(10,25,26,30)}. We performed a sensitivity-analysis and left out one study⁽¹⁰⁾ that had a high risk of bias due to a 10-year age difference between the intervention and the non-exposed group, which could explain a difference of 7dB hearing thresholds (calculated based on ISO 1990⁽⁴⁾). Sensitivity analysis results showed workers in a HLPP had a statistically non-significant 1.8 dB (95% CI -0.6 to 4.2) greater hearing loss at 4 kHz than non-exposed workers (very low-quality evidence, Table 10). The confidence interval includes a possible hearing loss of 4.2 dB which is similar to the level of hearing loss resulting from five years of exposure to 85 dB(A), which means workers might still be at risk of a clinically relevant hearing loss.

Table 10
SoF table - HLPP versus non-exposed workers (hearing loss)

Hearing loss prevention programme (HLPP) compared to non-exposed workers
Patient or population: workers Settings: exposure to noise Intervention: HLPP Comparison: non-exposed workers
Outcomes	Illustrative comparative risks* (95% CI)		Relative effect (95% CI)	No of participants (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Non-exposed workers	HLPP
Hearing loss Change in hearing threshold at 4 kHz in dB; Follow-up: mean 5 years	The mean hearing loss in the control groups was 3.6 dB at 4 kHz1	The mean hearing loss in the intervention groups was 1.8 dB higher (0.6 lower to 4.2 higher)		1846 (3 studies2)	very low3,4	pooled effect size 0.17 (95% CI -0.06 to 0.40) recalculated into dBs

• GRADE Working Group grades of evidence. High quality: we are very confident that the true effect lies close to that of the estimate of the effect; Moderate quality: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of effect, but there is a possibility that it is substantially different; Low quality: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect; Very low quality: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect
• ^*
  The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
• ¹
  Assumed increase of hearing threshold: median of three studies with respectively 3.4, 3.6 and 5.2 dB increase in hearing threshold at 4 kHz after five years' follow-up;
• ²
  Results from three of five studies were included in sensitivity analysis because one study was at serious risk of bias and one other study showed that in spite of hearing protection workers were still more at risk than non-exposed workers;
• ³
  We downgraded by one level from low to very low because three studies did not adjust for age and hearing loss at baseline;
• ⁴
  We would have downgraded by one more level because the confidence interval does not exclude a risk of hearing loss similar to exposure to 85 dB(A) but we had already reached a rating of very low quality evidence
• Caption: CI: Confidence interval; HLPP: hearing loss prevention programme

In addition, out of three other CBA studies that could not be included in the meta-analysis, two showed an increased risk of hearing loss in spite of the protection of a HLPP compared to non-exposed workers^(13,38) and one CBA did not⁽³³⁾.

DISCUSSION

We could not find any controlled studies, in which technical measures to reduce workers’ noise exposures were evaluated at the company level. Some argue that control groups are not necessary because the effect can be measured immediately⁽⁵⁵⁾. On the other hand, the measurement of noise levels in real working life can be biased by many operational and environmental factors. To address this issue, we systematically collected case studies. The immediate results of those studies are similar to those of HPDs. Noise control can potentially make HPDs in workplaces unnecessary, along with other components of hearing conservation programs. However, for most case studies, it was unclear if the measured reductions also effected personal noise level exposure. Other case studies measured personal noise exposure of workers but did not report measurement protocols and the personal effect remains uncertain. Moreover, long-term follow-up is missing and it is unclear if these are lasting solutions. Many potential biases in the uncontrolled studies would be remediated by the use of control groups, better reporting of noise measurement protocols and long-term follow-up measurements.

No studies evaluated the effectiveness of recommendations from occupational health services, national agencies or occupational health professionals to reduce noise levels. Regulations regarding noise at work can make it difficult to challenge current practice in experiments.

For immediate effects of HPDs, we restricted our inclusion criteria to field studies among workers and excluded studies that made use of volunteers or were carried out in the laboratory. All excluded studies showed a benefit of extra instruction compared to less or no instruction^(56-59). The increase in attenuation was similar to that found in our review. We only included studies that compared different devices worn by the same workers because the evaluation depends to a great extent on the wearer. That criterion excluded a great number of studies that evaluated different devices worn by different workers, but provided us with more reliable results.

Researchers who intended to evaluate a HLPP did not clearly define its implementation, which is especially important in studies comparing HLPPs. It is unclear if the results are applicable in other settings and what measures were taken in addition to HPDs (e.g. training).

The risk of bias was high (especially for long-term evaluation studies) because most studies were set up retrospectively and it is difficult to control confounders. Individual factors, such as skills necessary to correctly use HPDs or age, have an important effect on the outcome but only some studies used randomisation to ensure no baseline differences. Consequently, there is a need for better quality evidence. It has often been argued that randomisation of workers or workplaces is not possible but two studies that evaluated a HLPP (or components thereof) showed that randomisation was feasible, even in difficult sectors such as construction^(14,22). Evidence from more RCTs would eventually yield much higher-quality information on the effectiveness of hearing loss prevention programs.

Even though, we made significant efforts to search databases that would contain grey literature seeing that we did not go through conference proceedings. It is therefore possible that we missed retrospective cohort studies or controlled noise-reduction studies.

Publication bias could play a role in the results of the evaluation studies of HLPPs, with four of the studies being funded or carried out by people employed by the company responsible for the intervention, who could possibly have an interest in publishing studies demonstrating a preventative effect of HLPPs^(13,33).

Other authors drew similar conclusions to our review but mostly applied less systematic approaches.

One review located 22 studies that evaluated the field performance of many different types of HPDs worn by different workers^(60,61). The inclusion criteria of these studies were essentially different from ours because only studies comparing devices among the same subjects were included. However, the conclusions from all these studies are in agreement: under field conditions the noise attenuation of HPDs is much less than under laboratory conditions.

Another review concluded that the evidence from long-term evaluation studies does not support HLPPs’ effectiveness⁽⁶²⁾, but the search for studies was not systematic. The review included five studies, of which four were also included in this review. His conclusions for the effectiveness of HLPPs are similar to ours.

Authors from other studies reviewed occupational NIHL data⁽⁶³⁾, evaluated the quality of HLPPs in companies⁽⁶⁴⁾, or performed a narrative review directed at the mining sector alone⁽⁶⁵⁾. All studies concluded either that HLPPs are ineffective, or programs are commonly incomplete and miss noise control interventions.

There is very low-quality evidence that implementation of stricter legislation can reduce noise levels in workplaces. Case studies showed promising effects of engineering control on noise reduction at immediate follow-up but controlled studies and evaluation of the long-term effects are missing. It is unclear if results can be replicated in other workplaces and what the long-term effects are.

Under field conditions the average noise reduction of HPDs is lower than indicated ratings provided by the manufacturers. There is moderate-quality evidence that training of proper insertion of earplugs significantly reduces noise exposure at short-term follow-up but long-term follow-up is still needed.

There is very low-quality evidence that the better use of HPDs as part of HLPPs reduces the risk of hearing loss, whereas for other program components of HLPP we found no effect. The absence of conclusive evidence should not be interpreted as evidence of lack of effectiveness. Rather, it means that further research is very likely to have an important impact.

Future studies should use randomised design for HPDs or comparisons of different HLPPs or single programme components, or different levels of implementation in a cluster-randomised design. The ITS design has potential for evaluating HLPPs because much data is collected routinely.

CONCLUSION

Hearing loss prevention interventions modestly reduce noise exposure and hearing loss. Better quality studies and better implementation of noise control measures and HPDs is needed.

Disclaimer

The findings and conclusions in this report are those of the author(s) and do not necessarily represent the views of the National Institute for Occupational Safety and Health.

Appendix 1 Search strategy for CENTRAL

#1 MeSH descriptor Noise, Occupational explode all trees with qualifier: PC #2 noise AND (reduction OR abatement OR diminishment OR elimination OR “engineering controls” OR “administrative controls”) #3 “hearing loss prevention” OR “hearing conservation” OR “hearing surveillance” #4 “ear protective device” OR “ear protective devices” OR “hearing protective device” OR “hearing protective devices” OR “hearing protector” OR “hearing protectors” OR “hearing protection” OR “ear muffs” OR “ear plugs” OR “ear defenders” #5 (“noise reduction” AND “protective equipment”) #6 MeSH descriptor Noise, Occupational explode all trees #7 “protective equipment” #8 (#6 AND #7) #9 (#1 OR #2 OR #3 OR #4 OR #5 OR #8)

2016

#10 (#9) limited to publication year from 2008

Appendix 2 Search strategies for other databases

PubMed	Embase	CINAHL
2009 #1 noise [tiab] AND (reduction [tiab] OR abatement [tiab] OR diminishment [tiab] OR elimination [tiab] OR “engineering controls” [tiab] OR “administrative controls”[tiab]) #2 “hearing loss prevention” [tiab] OR “hearing conservation” [tiab] OR “hearing surveillance” [tiab] #3 “ear protective device” [tiab] OR “ear protective devices” [tiab] OR “hearing protective device” [tiab] OR “hearing protective devices” [tiab] OR “hearing protector” [tiab] OR “hearing protectors” [tiab] OR “hearing protection” [tiab] OR “ear muffs” [tiab] OR “ear plugs” [tiab] OR “ear defenders” [tiab] #4 (“noise reduction” [tiab] AND “protective equipment” [tiab]) #5 “Noise, Occupational/prevention and control”[Mesh] #6 “Noise, Occupational”[Mesh] #7 “protective equipment” [tiab] #8 #6 AND #7 #9 #1 OR #2 OR #3 OR #4 OR #5 OR #8 #10 (effect*[tiab] OR control*[tiab] OR evaluation*[tiab] OR program*[tiab]) AND (work*[tiab] OR worker*[tiab] OR workplace*[tiab] OR occupation*[tiab] OR prevention*[tiab] OR protect*[tiab]) #11 #9 AND #10 2012 #12 2008:2012[dp] #13 #11 AND #12 2015 #12 “2012”[Date - Publication]: “3000”[Date - Publication] #13 #11 AND #12 2016 #12 “2015/08/21”[Date - Publication]: “3000”[Date - Publication] #13 #11 AND #12	2009 1 industrial noise/ 2 (protective adj equipment).tw. 3 1 and 2 4 (noise and (reduction or abatement or diminishment or elimination or (engineering adj controls) or (administrative adj controls))).tw. 5 ((hearing adj loss adj prevention) or (hearing adj conservation) or (hearing adj surveillance)).tw. 6 ((ear adj protective adj device) or (ear adj protective adj devices) or (hearing adj protective adj device) or (hearing adj protective adj devices) or (hearing adj protecto) or (hearing adj protectors) or (hearing adj protection) or (ear adj muffs) or (ear adj plugs) or (ear adj defenders)).tw. 7 ((noise adj reduction) and (protective adj equipment)).tw 8 6 or 4 or 3 or 7 or 5 9 ((effect* or control* or evaluation* or program*) and (work or worker* or workplace* or working or occupation* or prevention* or protect*)).tw. 10 8 and 9 11 10 2012 #1 'industrial noise':de AND [2008-2012]/py #2 protective NEAR/3 equipment AND [2008-2012]/py #3 #1 AND #2 AND [2008-2012]/py #4 noise AND (reduction OR abatement OR diminishment OR elimination OR 'engineering controls' OR 'administrative controls') AND [2008-2012]/py #5 noise:ab,ti AND (reduction:ab,ti OR abatement:ab,ti OR diminishment:ab,ti OR elimination:ab,ti OR 'engineering controls':ab,ti OR 'administrative controls':ab,ti) AND [2008-2012]/py #6 'hearing loss' NEAR/5 prevention AND [2008-2012]/py #7 hearing NEAR/5 conservation AND [2008-2012]/py #8 'hearing surveillance' AND [2008-2012]/py #9 #6 OR #7 OR #8 AND [2008-2012]/py #10 ear NEAR/5 protective AND device* AND [2008-2012]/py #11 hearing NEAR/3 protect* AND [2008-2012]/py #12 ear NEAR/1 muff* AND [2008-2012]/py #13 ear NEAR/1 plug* AND [2008-2012]/py #14 ear NEAR/1 defender* AND [2008-2012]/py #15 #10 OR #11 OR #12 OR #13 OR #14 AND [2008-2012]/py #16 noise NEAR/1 reduct* AND protect* NEAR/1 equipm* AND [2008-2012]/py #17 #3 OR #4 OR #9 OR #15 OR #16 AND [2008-2012]/py #18 effect* OR control* OR evaluation* OR program* AND (work OR worker* OR workplace* OR working OR occupation* OR prevention* OR protect*) AND [2008-2012]/py #19 #17 AND #18 AND [2008-2012]/py #20 #19 AND [embase]/lim AND [2008-2012]/py #21 #20 NOT [medline]/lim AND [2008-2012]/py 2015 same search as in 2012; except change of time span [2008-2012]/py to [2012-2015]/py 2016 same search as in 2012; except change of time span [2012-2015]/py to [2015-2016]/py	2009 #1 (noise AND (reduction OR abatement OR diminishment OR elimination OR “engineering controls” OR “administrative controls”)) OR “hearing loss prevention” OR “hearing conservation” OR “hearing surveillance” #2 “ear protective device” OR “ear protective devices” OR “hearing protective device” OR “hearing protective devices” OR “hearing protector” OR “hearing protectors” OR “hearing protection” OR “ear muffs” OR “ear plugs” OR “ear defenders” #3 (noise(mh) AND “protective equipment”) OR (“noise reduction” AND “protective equipment”) #4 (effect* OR control* OR evaluation* OR program*) AND (work* OR worker* OR workplace* OR working OR occupation* OR prevention* OR protect*) #5 (#1 OR #2 OR #3) #6 (#4 AND #5) 2015 same strategy, #7 (#6) results limited to date of publication Jan 2012 - October 2016
BIOSIS/CAB Abstracts	Web of Science	NIOSHTIC/OSH UPDATE
2009 1 (noise and (reduction or abatement or diminishment or elimination or (engineering adj controls) or (administrative adj controls))).tw. 2 ((hearing adj loss adj prevention) or (hearing adj conservation) or (hearing adj surveillance)).tw. 3 ((ear adj protective adj device) or (ear adj protective adj devices) or (hearing adj protective adj device) or (hearing adj protective adj devices) or (hearing adj protecto) or (hearing adj protectors) or (hearing adj protection) or (ear adj muffs) or (ear adj plugs) or (ear adj defenders)).tw. 4 ((noise adj reduction) and (protective adj equipment)).tw 5 ((effect* or control* or evaluation* or program*) and (work or worker* or workplace* or working or occupation* or prevention* or protect*)).tw. 6 4 or 1 or 3 or 2 7 6 and 5	2009 #1 TS=(noise AND (reduction OR abatement OR diminishment OR elimination OR “engineering controls” OR “administrative controls”)) #2 TS=(“hearing loss prevention” OR “hearing conservation” OR “hearing surveillance”) #3 TS=(“ear protective device” OR “ear protective devices” OR “hearing protective device” OR “hearing protective devices” OR “hearing protector” OR “hearing protectors” OR “hearing protection” OR “ear muffs” OR “ear plugs” OR “ear defenders”) #4 #3 OR #2 OR #1 #5 TS=((effect* OR control* OR evaluation* OR program*) AND (work* OR worker* OR workplace* OR working OR occupation* OR prevention* OR protect*)) #6 #5 AND #4 2012 same as search in 2009, added time span 2008-2012 2016 same as search in 2009, added time span 2012-2016 #7 (#6) refined by: WEB OF SCIENCE CATEGORIES: (PUBLIC ENVIRONMENTAL OCCUPATIONAL HEALTH OR ACOUSTICS OR ENGINEERING MECHANICAL OR METALLURGY METALLURGICAL ENGINEERING OR ENGINEERING ENVIRONMENTAL OR MECHANICS OR ENGINEERING MANUFACTURING OR CONSTRUCTION BUILDING TECHNOLOGY OR ENGINEERING MULTIDISCIPLINARY OR TRANSPORTATION OR GEOSCIENCES MULTIDISCIPLINARY OR MEDICINE GENERAL INTERNAL OR OPERATIONS RESEARCH MANAGEMENT SCIENCE OR BEHAVIORAL SCIENCES OR ENGINEERING INDUSTRIAL OR ENGINEERING AEROSPACE OR MEDICINE RESEARCH EXPERIMENTAL OR AGRICULTURE MULTIDISCIPLINARY)	2009 NIOSHTIC (noise AND (induced OR hearing)) 2012 OSH UPDATE time span 01-2008 to 01-2012 Searched in bibliographic databases: International bibliographic, CISDOC, HSELINE, IRRST, NIOSHTIC, NIOSHTIC-2, RILOSH #1 DC{OUBIB OR OUCISD OR OUHSEL OR OUISST OR OUNIOC OR OUNIOS OR OURILO #2 GW{noise} #3 GW{induced OR hearing} #4 #2 AND #3 #5 #1 AND #4 #6 PY{2008 OR 2009 OR 2010 OR 2011 OR 2012} #7 #5 AND #6 2015 OSHupdate strategy same as in 2012, change of time span: # 6 PY{2012 OR 2013 OR 2014 OR 2015} 2016 OSHupdate all databases, strategy same as 2012, change of time span: #6 PY{2015 OR 2016}

ACKNOWLEDGEMENTS

We would like to thank the Dutch Ministry of Social Affairs and Employment, Stichting Arbouw, and the Cochrane Editorial Unit for the grants received to complete and update the review in 2009, 2012, and 2017. In addition, we would like to thank Jani Ruotsalainen from Cochrane Work and Jenny Bellorini from Cochrane ENT for their support. We also thank Bas Sorgdrager who contributed to an earlier version of the full review.

• Study conducted at the Cochrane Work Review Group, Finnish Institute of Occupational Health, Kuopio - Pohjois-Savo, Finland
• Financial support: nothing to declare.

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Publication Dates

• Publication in this collection
  03 Apr 2020
• Date of issue
  2020

History

• Received
  23 May 2019
• Accepted
  10 Sept 2019