Table 4:
Historical cohort studies
| Reference | Population | Exposure source | Exposure level | Methodology | Findings |
|---|---|---|---|---|---|
| (35) | Exposure group:100 Control group:31 |
Agro Industry | Exposure group SPL>85 dB(A) Control group SPL<85 dB(A) |
Noise measurement-Audiometric | Exposed group hearing loss=49% Control group=9.7% ( P value <0.001) OR=5.1(CI 95% =1.7–15.1) |
| (36) | Exposure group: 80 Control group:50 |
Esfahan group | Exposure group SPL>95 dB(A) Control group65 <SPL<95 dB(A) |
Noise measurement-Audiometric | Hearing threshold difference in 2000Hz frequency and higher in the exposure and case groups (
P
value
<0.05) Exposure group Hearing damage, 22.3%, control group 3.8% ( P value <0.05) |
| (2) | Exposure group: 140 Control group:140 |
Five noisy workshops in petrochemical industry | Exposure group SPL>85 dB(A) Control group SPL=55 dB(A) |
Noise measurement-Audiometric | The prevalence of hearing loss in the Exposure group,38.5% - case group 7.8% ( P value <0.001) |