Prevalence of PCHI by the age of entry to primary school in the combined cohort of 100 096 with comparison of the three cohorts (total number of PCHIs in combined cohort=378)
| Degree of hearing impairment PTA average 500–4000 Hz Better hearing ear in bilateral Worse hearing ear in unilateral | Prevalence (95% CI) in combined cohort | Difference in prevalence in the three cohorts (df=2), Pearson χ2 (p) | |
|---|---|---|---|
| Bilateral PCHI | Mild (20–39 dB HL) | 1.24 (1.02 to 1.46) | 0.302 (0.860) |
| Moderate (40–69 dB HL) | 0.78 (0.61 to 0.95) | 0.292 (0.864) | |
| Severe (70–95 dB HL) | 0.38 (0.26 to 0.5) | 0.359 (0.836) | |
| Profound (>95 dB HL) | 0.35 (0.23 to 0.47) | 0.125 (0.937) | |
| Moderate and worse (>40 dB HL) | 1.51 (1.27 to 1.75) | 0.012 (0.994) | |
| Total bilateral | 2.75 (2.42 to 3.07) | 0.144 (0.930) | |
| Unilateral PCHI | Mild and moderate (20–69 dB HL) | 0.44 (0.31 to 0.57) | 0.505 (0.777) |
| Severe and profound (>70 dB HL) | 0.59 (0.44 to 0.74)** | 10.35 (0.006)** | |
| Total unilateral | 1.03 (0.83 to 1.23)* | 8.27 (0.016)* | |
| Total | 3.78 (3.4 to 4.16) | 1.764 (0.414) | |