Table 1

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 unilateralPrevalence (95% CI) in combined cohortDifference in prevalence in the three cohorts (df=2), Pearson χ2 (p)
Bilateral PCHIMild (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 bilateral2.75 (2.42 to 3.07)0.144 (0.930)
Unilateral PCHIMild 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 unilateral1.03 (0.83 to 1.23)*8.27 (0.016)*
Total3.78 (3.4 to 4.16)1.764 (0.414)
  • HL, hearing level; PCHI, permanent childhood hearing impairment; PTA, pure-tone average.

  • * p<0.05;

  • ** p<0.01.