Table 2

Average rate of hearing loss (dB/year) before and after initiation of daily noise exposure monitoring

Intervention groupControl groupDifference in difference*p Value
No.BeforeAfterNo.BeforeAfter
All intervention subjects801.7 (1.3)−0.5 (1.9)
Matched on age, gender, baseline hearing781.8 (1.3)−0.4 (1.5)2340.4 (1.1)−0.1 (2.1)1.7<0.0001
Matched on age, gender, baseline hearing and initial rate of hearing loss461.4 (1.5)−0.2 (1.6)1381.1 (1.1)0.45 (1.45)1.00.06
  • * Difference in the difference between the pre-intervention (2000–2004) and post-intervention time periods (2006–2010).