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

Tikka, Christina; Verbeek, Jos; Kateman, Erik; Morata, Thais Catalani; Dreschler, Wouter; Ferrite, Silvia

doi:10.1590/2317-1782/20192019127

person Christina Tikka

schoolCochrane Work Review Group, Työterveyslaitos - Kuopio, Finland.

0000-0003-2078-8715

person Jos Verbeek

schoolCochrane Work Review Group, Työterveyslaitos - Kuopio, Finland.

0000-0002-6537-6100

person Erik Kateman

schoolTronada Consult, Doetinchem - Netherlands.

0000-0003-4487-5039

person Thais Catalani Morata

schoolNational Institute for Occupational Safety and Health – NIOSH – Cincinnati (OH), USA.

0000-0002-0320-9649

person Wouter Dreschler

schoolClinical & Experimental Audiology, Academic Medical Centre - Amsterdam, Netherlands.

0000-0002-4192-6104

person Silvia Ferrite

schoolDepartamento de Fonoaudiologia, Universidade Federal da Bahia – UFBA - Salvador (BA), Brasil.

0000-0001-5344-3751

Conflict of interests: nothing to declare.

Correspondence address: Christina Tikka Cochrane Work Review Group, Finnish Institute of Occupational Health PO Box 310, Kuopio, 70101, Finland. E-mail:
christina.tikka@ttl.fi

Author contributions CT participated in searching, eligibility screening, quality assessment, data extraction, data analysis, writing and update of the text, comment on drafts of protocol and review and is the guarantor of this review; JHV participated in protocol development, searching, eligibility screening, quality assessment, data extraction, data analysis, writing and update of the text, comment on drafts of protocol and review; EK participated in protocol development, searching for trials, eligibility screening, quality assessment of studies, data extraction, review development, comment on drafts of protocol and review; TCM participated in searching for studies, eligibility screening, data extraction, update of the text, comment on drafts of protocol and review, and review of translation into Portuguese; WAD participated in eligibility screening, data extraction, comment on drafts of protocol and review. SF participated in eligibility screening, data extraction, comment on drafts of protocol and review, translation into Portuguese.

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⁾

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

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

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

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

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)	OR 0.8 (0.63 to 1.03)	3242 (2 CBA studies)	very low 1

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

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

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)

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

[1] 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

[TFN1] ^a
Final grading of quality of evidence, between brackets domain that led to down/upgrading the quality

[3] 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

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