Summary of findings for the main comparison. Stricter legislation for noise exposure.
| Stricter legislation compared with existing legislation for noise exposure | |||||
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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 | ||||
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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) |
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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 low1 | |
| *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). CI: Confidence interval; PEL: permissible exposure level | |||||
| 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 | |||||
1We downgraded by one level from low to very low because there is only one study and it has a high risk of bias.