R&D Portfolio - Research Goal 4.2:
Characterize hearing ability in the general population through national databases
Accurate reference population data are essential for determining excess risk of hearing loss due to occupational exposures. Current reference databases are derived from audiometric data collected in the 1960s and 1970s,, data collected from one regional area, or self-assessed hearing ability which can result in underestimation of hearing trouble.
In 1988, the HLR program recommended that hearing data for unexposed populations be collected to serve as a baseline for comparison to the hearing of groups exposed to noise. Such hearing threshold norms should be established as a function of demographic factors. The HLR program further suggested that this data could be obtained through national health surveys such as the NHANES. In 1996, NORA underscored the need for a contemporary audiometric database, commenting that, “reliance on data collected thirty years ago results in predictions that underestimate the amount of hearing loss that is due to occupational noise.”
NHANES is a program conducted by NCHS. It collects nationally-representative data on the health and nutritional status of the civilian, non-institutionalized population of the U.S. through questionnaires, physical examinations, and laboratory analyses. This survey provides a statistically powerful “snapshot” of the health of Americans.
In 1998, the HLR program partnered with NCHS, the manager of NHANES, and NICDC to institute testing of working age adults. Audiometric testing has been conducted in every cycle of the NHANES survey. Hearing testing in adults aged 20-29 was included for the six-year cycle of the survey that was completed in 2004. In addition to hearing data, the survey collected information on occupational and non-occupational noise exposures, personal protective behaviors and other relevant health factors. The HLR program provided the technical oversight of the current NHANES audiometry component, including protocol and questionnaire development, technician training, and monitoring of data collection and quality assurance.
NHANES data collected from 1999-2002 are available, are currently being analyzed and publications are being prepared. Data from the 2003-2004 NHANES will complete the working aged adult hearing database and should be available by 2006.
While NHANES is filling a longstanding research need in occupational hearing loss research, it initially only collected cross-sectional data through age 69. The HLR program has been involved in other studies that address these limitations. The Age, Gene/Environment Susceptibility Study (AGES) is the current phase of a prospective research program established in 1967 known as the Reykjavik Study. The project has collected longitudinal data from a cohort of more than 20,000 individuals resident in the Reykjavik area and born between 1907 and 1934. The primary purpose of AGES is to sequence the human genome and identify candidate genes that will allow substantial innovation in the epidemiologic study of aging. AGES is also conducting audiometric testing on approximately 10,000 individuals aged 67 and older participating in this phase of the project. The HLR program is providing technical assistance with the audiometric portion of this study, which is designed to be essentially identical to the NHANES protocol. Data collection for the AGES project will continue through 2006 and be available for analysis shortly thereafter.
The Fels Longitudinal Study began in 1929 and is the world’s longest running study on human growth, body composition, maturation, and aging. The first participants were enrolled prenatally and are now in their mid-seventies. Children, grandchildren, and even great-grandchildren of the original participants are now enrolled. From 1977-1983, hearing thresholds and noise exposures were serially collected on children and young adults in the Fels program to study how hearing ability develops in humans relative to various individual and environmental factors. In 2003, Fels researchers at the Wright State University approached HLR program staff for assistance with conducting repeat audiometric testing on both the youths tested from 1977-1983 (now adults) as well as their children. HLR program researchers provide training to the Fels staff, assist with equipment maintenance and calibration, and will cooperate in the analysis of the audiometric data. Initial results from the Fels study should be available in 2007.
Glorig A & Roberts J . Hearing levels of adults by age and sex: United States, 1960-1962. Vital and Health Statistics, Series 11, No. 11. (PHS) 1000.
Rowland M . Basic data on hearing levels of adults 25-74 years: United States, 1971-75. Vital and Health Statistics, Series 11, No. 215.
ANSI S3.44 . American National Standard: Determination of Occupational Noise Exposure and Estimation of Noise-Induced Hearing Impairment.
NCHS . Summary health statistics for U.S. adults: National Health Interview Survey, 2003. Vital and Health Statistics, Series 10, No. 225 (PHS) 2005-1553.
NIOSH . Proposed National Strategies for the Prevention of Leading Work-Related Diseases and Injuries , Part 2. Assoc. School of Public Health.
NIOSH . National Occupational Research Agenda. DHHS (NIOSH) Publication No. 96-115.