Brink 2002.

Methods	CBA study
Participants	Automobile workers n = 264 USA 1 automobile company
Interventions	Intervention: wearing hearing protection > 33% of the time; n = 132 Control: wearing hearing protection < 33% of the time; n = 132
Outcomes	Hearing thresholds at 0.5, 1, 2, 3, 4 kHz 14‐year follow‐up
Notes	Long‐term Comparability ‐ intervention/control: age: ? hearing: ?
Risk of bias
Bias	Authors' judgement	Support for judgement
14. Blinding (subjects)	High risk	no blinding
15. Blinding (outcome assessors)	High risk	no blinding
16. Retrospective unplanned subgroup analyses	Low risk	no additional analyses
17. Follow‐up	Unclear risk	not reported
18. Statistical tests	Low risk	ANOVA
19. Compliance	Low risk	HPD use measured
20. Outcome measures	Low risk	audiometry quality reported (STS)
21. Selection bias (population)	Low risk	same population
22. Selection bias (time)	Low risk	same time
23. Randomization	High risk	no randomisation
24. Allocation concealment	Unclear risk	no randomisation, not applicable
25. Adjustment for confounding	Unclear risk	no difference in age
26. Incomplete outcome data	Unclear risk	not reported