CDC study shows hearing loss as third most common chronic condition

Hearing loss is the third most common chronic physical condition in the United States, and is more prevalent than diabetes or cancer. Occupational hearing loss, primarily caused by high noise exposure, is the most common U.S. work-related illness. Approximately 22 million U.S. workers are exposed to hazardous occupational noise. CDC compared the prevalence of hearing impairment within nine U.S. industry sectors using 1,413,789 noise-exposed worker audiograms from CDC’s National Institute for Occupational Safety and Health (NIOSH) Occupational Hearing Loss Surveillance Project. CDC estimated the prevalence at six hearing impairment levels, measured in the better ear, and the impact on quality of life expressed as annual disability-adjusted life years (DALYs), as defined by the 2013 Global Burden of Disease (GBD) study. The mining sector had the highest prevalence of workers with any hearing impairment, and with moderate or worse impairment, followed by the construction and manufacturing sectors. Hearing loss prevention, and early detection and intervention to avoid additional hearing loss, are critical to preserve worker quality of life.

Conducting the study

The NIOSH Occupational Hearing Loss Surveillance Project collects de-identified audiograms for U.S. workers who were tested to comply with regulatory requirements because of high occupational noise exposure, defined as ≥85 decibels on the A-scale (dBA). Audiometric service providers and others that perform worker testing agreed to share these data with NIOSH. A cross-sectional retrospective cohort analysis was conducted using the last audiogram completed for each worker during 2003–2012. Audiograms missing necessary fields or with other quality issues, having hearing threshold values that suggested testing errors, or displaying attributes unlikely to be primarily caused by occupational exposures, were excluded. Industries were classified using the 2007 North American Industry Classification System.

The prevalences of six severity levels of hearing impairment were calculated for workers in each industry sector using the audiometric definitions from the GBD Study, except that workers in this sample who had hearing aids did not wear them during testing. DALYs representing the number of healthy years lost per 1,000 workers each year were calculated by industry sector using the GBD Study disability weights.

Tinnitus information required to calculate the DALYs was not available in the NIOSH Occupational Hearing Loss Surveillance Project sample and was estimated using results from previous studies.

Understanding the results

The final sample included 1,413,789 audiograms for workers employed by 25,908 U.S. companies during 2003–2012. Among 99 percent of audiograms for which information on the worker’s sex was available, 78 percent were recorded for males and 22 percent for females. A greater percentage of males had any hearing impairment (14 percent) than did females (seven percent), and the prevalence and severity of impairment increased with age for both sexes. Among all industries, 13 percent of noise-exposed workers had any impairment and two percent had moderate or worse impairment. Workers with hearing impairment were represented in all industry sectors, with sharply decreasing numbers of workers with higher levels of impairment. The mining sector had the highest prevalence of workers with any impairment (17 percent) and with moderate or worse impairment (three percent), followed by the construction sector (any impairment = 16 percent, moderate or worse impairment = three percent), and the manufacturing sector (14 percent and two percent). The public safety sector, which includes police protection, fire protection (including wildland firefighters), corrections and ambulance services, had the lowest prevalence of workers with any impairment ( seven percent).

Across all industries, 2.53 healthy years were lost annually per 1,000 noise-exposed workers. Mild impairment accounted for 52 percent of all healthy years lost and moderate impairment accounted for 27 percent. Workers in the mining and construction sectors lost 3.45 and 3.09 healthy years per 1,000 workers, respectively. Overall, 66 percent of the sample worked in the manufacturing sector and represented 70 percent of healthy years lost by all workers. Public safety workers lost 1.30 healthy years per 1,000 workers, the fewest among all workers.

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