Epidemiology of noise-induced hearing loss in New Zealand

Introduction: Hearing loss is a major cause of disability in the world. Occupational noise exposure is likely to contribute to a very high proportion of the cases of hearing loss in adults. Concern has been raised by the Accident Compensation Corporation (ACC) in New Zealand about the fact that the number of new cases of noise-induced hearing loss (NIHL) is not declining, despite the health and safety legislation and establishment of hearing conservation programmes in industry. To inform strategies for prevention, a review of the burden of NIHL in New Zealand was undertaken, particularly focusing on the trends in compensation claims and costs, and the associated sociodemographic patterns. Methods: A review of the peer-reviewed published literature was conducted to identify national and international estimates of NIHL prevalence. The ACC claims dataset (July 1995 to June 2006) was analysed to describe annual trends in new NIHL claims, cost to d claimants' age, gender and occupational group. Results: There is currently no reliable information regarding the overall incidence and prevalence of NIHL in New Zealand. ACC data reveals a substantial increase in the number of new NIHL claims annually, rising from 2823 in July 1995-June 1996, to 5580 in July 2005-June 2006. Together with ongoing claims the overall costs of NIHL claims increased by an average of 20% each year (a six-fold increase over the decade) resulting in a total cost to ACC of $193.82M over the review period. Collectively, agriculture and fisheries workers, trades workers, machine operators, and assemblers accounted for 53% of new claims. Most claims were lodged in middle age or later, with the vast majority of claimants (95%) being men. The relationship of age with the probability of making a claim changed significantly over the study period with rates in older age groups increasing faster than in younger. Conclusions: The substantial and increasing societal costs despite decades of NIHL control legislation suggests that current strategies addressing this problem are not effective, inadequately implemented, or both.