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Recreational Firearm Use and Hearing Loss
David M. Nondahl, MS;
Karen J. Cruickshanks, PhD;
Terry L. Wiley, PhD;
Ronald Klein, MD;
Barbara E. K. Klein, MD;
Ted S. Tweed, MS
Arch Fam Med. 2000;9:352-357.
ABSTRACT
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Objective To assess the relation between recreational firearm use and high-frequency hearing loss in a population of older adults.
Design Cross-sectional, population-based cohort study.
Setting The midwestern community of Beaver Dam, Wis.
Participants A population-based sample of 3753 participants (83% of those eligible), aged 48 to 92 years, participated in the baseline phase of the Epidemiology of Hearing Loss Study.
Intervention None.
Main Outcome Measures Lifetime and past year self-reported firearm use during target shooting and hunting were assessed by interview. Hearing thresholds were measured by pure-tone audiometry.
Results After age and other factors were adjusted for, men (n=1538) who had ever regularly engaged in target shooting (odds ratio, 1.57; 95% confidence interval, 1.12-2.19) or who had done so in the past year (odds ratio, 2.00; 95% confidence interval, 1.15-3.46) were more likely to have a marked high-frequency hearing loss than those who had not. Risk of having a marked high-frequency hearing loss increased 7% for every 5 years the men had hunted (odds ratio, 1.07; 95% confidence interval, 1.03-1.12). Thirty-eight percent of the target shooters and 95% of the hunters reported never wearing hearing protection while shooting in the past year.
Conclusions These results indicate that use of recreational firearms is associated with marked high-frequency hearing loss in men. There is a need for further education of users of recreational firearms regarding the risk of hearing impairment associated with firearm use and the availability and importance of appropriate hearing protection.
INTRODUCTION
HEARING LOSS is one of the most common chronic conditions affecting older adults in the United States.1 A population-based study in Wisconsin reported that almost half of the adults aged 48 to 92 years had at least mild hearing loss.2 Hearing loss can have wide-ranging effects, including depression, decreased socialization, reduced personal safety and security, and misdiagnosis of medical or emotional problems.3
Many factors may contribute to the onset of hearing loss in adults, including aging, exposure to noise, and the biological effects of diseases and ototoxic agents.4 The deleterious effects of excessive occupational noise exposure are well documented.5-8 Exposure to impulse noise from small-caliber and large-caliber firearms during military service, for example, can lead to hearing loss resulting from acute acoustic trauma or cumulative exposure,9-13 and has been associated with subclinical disturbances of the vestibular system.14
Much less is known about the effects of recreational firearm use on hearing loss. Taylor and Williams15 demonstrated significantly worse hearing among 103 sports hunters than 21 controls. A few studies have assessed the effect of recreational firearm use among railroad and forest workers; each study reported reduced high-frequency hearing among the firearm users compared with nonusers.16-18 Clark19 concluded that, among leisure activities, hunting and target shooting are among the most serious threats to hearing. However, we know of no population-based epidemiological study of the association between recreational firearm use and hearing loss in the United States. Accordingly, the purpose of this study was to assess the association between the use of recreational firearms and hearing loss in older adults.
SUBJECTS AND METHODS
Participants were 1538 men who had participated in the Epidemiology of Hearing Loss Study,2 a population-based study of hearing loss in adults aged 48 to 92 years. During 1987 to 1988, residents of the city or township of Beaver Dam, Wis, who were 43 to 84 years of age (N=5924) were identified through a private census and invited to participate in a study of age-related ocular disorders (The Beaver Dam Eye Study, 1988-1990, N=4926).20 All those who participated in the baseline eye examination and were alive as of March 1, 1993, were eligible to participate in the Epidemiology of Hearing Loss Study (N=4541). Of those eligible, 3753 (82.6%) participated, 42.3% of whom were men.
The study was approved by the Human Subjects Committee of the University of Wisconsin, Madison. Informed consent was obtained from each participant at the beginning of the examination. The Epidemiology of Hearing Loss Study examination included a questionnaire about medical and family history, self-reported hearing handicap,21 and occupational and leisure noise exposure. The hunting and target shooting sections of the questionnaire focused on shooting history, type of firearm used most often, and use of hearing protection. Participants were asked if they had ever engaged in target shooting at least once a month (on average) for 1 year or if they had ever gone hunting and fired their gun. If the participant had done either, additional questions were asked to obtain a more detailed exposure history.
Audiology tests included otoscopy,22 screening tympanometry22-23 pure-tone air and bone conduction audiometry,2 and word recognition.24 All audiometric and tympanometric equipment complied with American National Standards Institute standards.25-26 Pure-tone audiometric testing was performed in accordance with recommended American Speech-Language-Hearing Association (ASHA) procedures.27 For 96.3% of the participants with audiometric data, audiometric testing was conducted in a sound-treated booth meeting American National Standards Institute specifications regarding ambient noise.28 The audiometers (Virtual 320; Virtual Corporation, Portland, Ore) were controlled by a Macintosh computer. The remaining 3.7% of the participants were tested at their home (n=62), at a nursing home (n=63), or at a group home (n=7) using a Beltone 112 portable audiometer (Beltone Electronic Corp, Chicago, Ill) with E-A-Rtone 3A insert earphones (Cabot Safety Corp, Indianapolis, Ind) to attenuate ambient noise. When portable equipment was used, sound levels were recorded before and after testing to ensure that ambient noise levels were within standards.28 Audiometers were calibrated every 6 months.
Analyses focus on hearing thresholds from 4 kHz to 8 kHz, a frequency range likely to be affected by exposure to small-caliber firearms.15, 29 For participants with no response at a given frequency, the hearing threshold was set to 5 dB above the maximum output of the audiometer at that frequency. This procedure allowed data from participants with severe hearing loss to be included in analyses rather than be omitted as missing values. A marked high-frequency hearing loss was defined as the pure-tone average (PTA) of hearing thresholds at 4, 6, and 8 kHz greater than 60-dB HL (decibels in hearing level) in the worse ear. Because older adults often had a degree of hearing loss in these higher frequencies (Table 1), a cutoff of 60 dB was chosen to identify those with greater losses. Worse ear measures were assessed to account for any asymmetry between ears.
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Table 1. High-Frequency Hearing Status, Based on the Pure-Tone Average of Hearing Thresholds at 4, 6, and 8 kHz in the Worse Ear
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Word recognition scores on an auditory test that used a competing message (50 words per test version) to measure hearing (Northwestern University Auditory Test No. 6 by a female speaker on compact disc, version 1.130) were assessed as a measure of hearing function. Word recognition tests were performed at 36 dB above each participant's audiometric threshold at 2000 Hz for the better ear. The competing message (a male voice) was presented at a signal-to-noise level of +8.
Self-reported hearing handicap was assessed using the 10-question Hearing Handicap Inventory for the Elderly—Screening Version test.21 The Hearing Handicap Inventory for the Elderly—Screening Version test was designed to measure the perceived social-situational and emotional effects of hearing loss among the elderly, resulting in an index of perceived hearing disability or handicap that ranges from 0 to 40. In accordance with American Speech-Language-Hearing Association guidelines,31 a self-reported hearing handicap was defined as a total score greater than 8.
Age, smoking status (never, past, or current), alcohol consumption (grams of ethanol per week and history of heavy drinking, defined as 4 or more drinks per day), history of cardiovascular disease (myocardial infarction, stroke, or angina), educational attainment, history of occupational noise exposure, leisure time noise exposure, and history of head injury (skull fracture, concussion, broken nose, loss of consciousness due to a head injury, or whiplash or other serious neck injury) were the potential confounding variables used in statistical modeling. A history of occupational noise exposure was defined as having had a full-time job for which speaking in a raised voice or louder was necessary to be heard within 0.6 m of a person; having driven a tractor at least half of the time without a cab; or having worked in the military in front-line warfare, in a tank or plane, in the engine room of a ship, using heavy artillery, or on weapons ranges at least 7 times in 1 year. Leisure time noise exposure was defined as the number of noisy activities (0 to 5) to which the participant had been exposed at least once a month, on average, for a year. The 5 noisy activities were woodworking; metalworking; driving a motorcycle, all-terrain vehicle, race car, motorboat, or snowmobile; using outdoor power tools such as lawn mowers, leaf blowers, snowblowers and rototillers; and using a chain saw. By including these factors (when statistically significant) in logistic regression and analysis of covariance models, their influence was held constant so that the relationship between shooting recreational firearms and hearing loss could be more clearly determined. Statistical analyses were completed with SAS statistical software.32
RESULTS
The prevalence of recreational firearm use was low among women, both for target shooting (ever, 3.3%; past year, 0.1%) and hunting (ever, 11.3%; past year, 0.5%). Consequently, the current study focused on men. Data from 49 men who completed the interview but refused the examination were excluded from analyses, as were data from 2 additional men with incomplete audiometric testing, resulting in data that could be analyzed for 1538 men. Selected characteristics of these 1538 men are summarized in Table 2. Most men (79%) had a history of occupational noise exposure. About half of the men (52%) had a marked high-frequency hearing loss.
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Table 2. Characteristics of 1538 Male Participants
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The prevalence of hunting (ever, 74.9%; past year, 21.2%) was much higher than the prevalence of target shooting (ever, 15.6%; past year, 4.8%). The median number of shots taken by hunters in the past year was 10 and the median number of hours spent target shooting in the past year was 23.
Target shooters used shotguns (54%), rifles (29%), and handguns (17%) as their main type of firearm. Shotguns were predominantly 12-gauge (92%); the most common caliber of rifle was .22 (30%), followed by .30 (15%) and 30 to 06 (15%). Most hunters used shotguns (53%) and rifles (46%). Their shotguns were also predominantly 12-gauge (87%), while the caliber of rifles varied (30-06, 45%; .308, 11%; 30-30, 10%; .270, 8%; other, 26%).
Figure 1 shows mean hearing thresholds (worse ear) for 3 groups of men: those who had never hunted or engaged in target shooting, those who had a history of hunting (ever), and those who had a history of both hunting and target shooting. (The 10 men with only a history of target shooting are excluded from Figure 1 owing to small sample size.) After age, smoking status, alcohol consumption, education, history of occupational noise exposure, leisure time noise exposure, and history of head injury were adjusted for, mean thresholds for the 230 men who had engaged in both activities were significantly worse than mean thresholds for men who had a history of hunting only (2-8 kHz, P<.05) or who had never participated in either activity (2-6 kHz, P<.05). Furthermore, mean thresholds for the 922 men with a history of hunting were not significantly different from mean thresholds for the 376 men who had never participated in either activity. This suggests that a history of target shooting may have had a greater effect on mean thresholds than did a history of hunting.
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Mean hearing thresholds according to recreational firearm exposure history (men only). Means are adjusted for age, smoking status, alcohol consumption, education, history of occupational noise exposure, leisure time noise exposure, and history of head injury. Neither indicates no history of hunting or target shooting; hunting only, history of hunting, but not target shooting; hunting and target shooting, history of both target shooting and hunting.
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After age, smoking status, education, history of occupational noise exposure, leisure time noise exposure, and history of head injury were adjusted for, high-frequency PTAs (4, 6, and 8 kHz) tended to worsen as shooting duration increased (Table 3).
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Table 3. Hearing Sensitivity, Word Recognition Performance in Competing Message, and Prevalence of Self-reported Hearing Handicap by Duration of Exposure to Firearms During Target Shooting and Hunting (Men Only)*
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After adjusting for age and other factors, word recognition scores on the auditory test30 were not significantly associated with number of years of target shooting (Table 3). Among hunters, the decreasing linear trend with exposure was statistically significant, but the differences in scores were quite small and not clinically significant (Table 3).
The adjusted prevalence of self-reported hearing handicap tended to increase with the number of years of target shooting (Table 3), but not with years of hunting (Table 3).
Previous investigators have noted that hearing thresholds in the left ear, particularly at the higher frequencies, are usually worse than those in the right ear among military firearm users.13, 15-16,33 In the present study, this pattern was apparent both for recreational firearm users and nonusers. However, the largest mean threshold differences between left and right ears (4 to 8 dB for 3 to 8 kHz) occurred among men with a history of hunting or a history of both target shooting and hunting. This pattern remained after adjusting for handedness (right/left/ambidextrous).
Multiple logistic regression models were used to assess the risk of having a marked high-frequency hearing loss after adjusting for age, smoking status, alcohol consumption, education, history of occupational noise exposure, leisure time noise exposure, and history of head injury. Target shooting was associated with having a marked high-frequency hearing loss (ever: odds ratio [OR], 1.57; 95% confidence interval [CI], 1.12-2.19; past year: OR, 2.00; 95% CI, 1.15-3.46). Men who had hunted in the past year were approximately 1.4 times as likely to have a marked high-frequency hearing loss as men who had not (OR, 1.36; 95% CI, 1.01-1.84).
For each 5 years that men had hunted, the odds of having a marked high-frequency hearing loss increased by 7% (OR, 1.07; 95% CI, 1.03-1.12). Results were similar for every 5 years of target shooting (OR, 1.09; 95% CI, 0.98-1.21), but were not statistically significant. Logistic regression modeling yielded no significant associations between recreational firearm use and hearing loss in the audiometric speech frequencies (0.5, 1, and 2 kHz).
Almost all hunters (95%) reported that they had never worn hearing protection while shooting during the past year. Among target shooters, 38% reported never wearing hearing protection while shooting during the past year, 49% reported that they always wore hearing protection, and 13% reported that they sometimes did. There were no significant differences in mean hearing thresholds or PTA between target shooters who always wore hearing protection the previous year (n=36) and those who never did (n=28).
COMMENT
Histories of target shooting (ever: OR, 1.57; past year: OR, 2.00) and hunting (past year: OR, 1.36) were associated with marked high-frequency hearing loss in men. Mean high-frequency PTAs worsened with increased years of shooting, even after adjusting for age and other factors. These results are consistent with studies that have demonstrated worsened hearing among military recruits exposed to impact noise from small-caliber and large-caliber firearms.9-13
Most shoulder-supported weapons used for target shooting and hunting were small-caliber rifles or 12-gauge shotguns. These weapons produce a peak sound pressure level in excess of 140 dB,34-36 a level representing risk of cochlear and associated hearing damage.37 These small-caliber firearms are likely to affect hearing at a higher frequency range than would larger-caliber military weapons such as bazookas, cannons, or antitank guns.9, 37-38 Consequently, this study focused on hearing impairment in the high-frequency range (4, 6, or 8 kHz). As it is common for older men to have some degree of hearing impairment at these frequencies,4 a marked high-frequency loss (PTA > 60 dB HL) was chosen as the outcome of interest.
The median number of hours spent target shooting in the past year was 23 hours. Hunters shot their guns a median of 10 times in a similar period. While 81% of recent (past year) target shooters also hunted, only 18% of recent hunters were target shooters. It is clear that, on average, target shooting resulted in a much greater cumulative exposure to impulse noise than did hunting in a similar period. This may explain, in part, why ORs for target shooters tended to be higher than corresponding ORs for hunters even though some target shooters were more likely to wear hearing protection. Nevertheless, there was enough cumulative exposure among hunters (median, 20 years) to result in an estimated 7% increase in likelihood of having a marked high-frequency hearing loss for every 5 years of hunting.
Previous studies13, 15-16,33 have noted that, among firearm users in the military, hearing thresholds in the left ear are usually worse than those in the right ear, particularly for the higher frequencies. This is typically attributed to the head-shadow effect that occurs as a weapon is sighted and fired while supported with the right shoulder.39 The head is turned in such a way that the right ear is more protected from the impulse noise of the firearm, while the left ear is more directly in line with the noise source. In the present study, mean differences in hearing thresholds between right and left ears were consistent with the head-shadow effect, in that the left ear disadvantage tended to be greater for high-frequency thresholds, and greater among shooters than nonshooters.
Figure 1 suggests that, after adjusting for age and other factors, a history of target shooting may have had a greater effect on mean thresholds at 2 to 8 kHz than did a history of hunting. The pattern of mean thresholds shown in Figure 1 may be explained in part by the fact that men who had a history of both hunting and target shooting had a longer hunting history (mean, 38 years) than men who had a history of hunting only (mean, 28 years). Accordingly, Figure 1 reflects cumulative duration of exposure as well as presence of exposure. Nevertheless, the pattern is consistent with the fact that target shooting resulted in a much greater exposure to impulse noise than did hunting in a similar period.
The current study is, to our knowledge, the first large, population-based study of the association between recreational firearm use and hearing loss in the United States. Although the firearm data are based on self-report, the presence of a relationship between years of target shooting or hunting and high-frequency hearing sensitivity suggests that those measures of exposure serve as an index of actual exposure. In an older population, relying on recall to derive a more precise estimate of actual duration and intensity of lifelong cumulative exposure is unlikely to yield a better measure of exposure.
Scores from a word recognition test that used a competing message to assess hearing30 and from the Hearing Handicap Inventory for the Elderly—Screening Version test21 were used to assess hearing function and self-reported hearing handicap, respectively, in the frequencies important for understanding speech (0.5-2 kHz).24, 40 The prevalence of self-reported hearing handicap was higher for long-term target shooters than for shorter-term target shooters, suggesting that prolonged exposure to firearms from target shooting may have an emotional and social effect as well as the previously suggested effect on hearing sensitivity at higher frequencies.
Because of the cross-sectional nature of the study, we do not have audiometric measurements on participants before their exposure to firearms. Consequently, while we have demonstrated an association between the use of recreational firearms and high-frequency hearing loss in men, a causal relationship cannot be definitively established through this study alone.
Hearing protection is underused: 38% of target shooters and 95% of hunters never wore hearing protection while shooting during the past year. Taylor and Williams15 found that 96% of hunters never wore hearing protection. The hunter is interested in sounds that help him find his prey, warn him of danger, and help him communicate with his hunting partners. The inability to hear these sounds could seriously undermine a successful hunt, and in some cases could endanger the lives of the hunters. Well-fitting, level-dependent earplugs have been suggested as one solution to this dilemma, having been shown in experimental conditions to protect the ear and to allow good speech communication at a distance of up to 63 m.29, 41
There were no significant differences in mean hearing thresholds or PTA between target shooters who always wore hearing protection the previous year (n=36) and those who never did (n=28). However, data on the use of hearing protection were gathered only for the previous year. Habits regarding the use of hearing protection may have been different in earlier years.
The prevalence of target shooting and hunting within the past year was 4.7% and 21.2%, respectively, among men in this midwestern community. Based on 1990 US census figures from 199242 for men in the same age range, in a given year this would project to 1.5 million male target shooters and 6.9 million male hunters in the United States aged 48 to 90 years. The National Sporting Goods Association estimated that in 1998, 17.3 million persons 7 years or older in the United States hunted with firearms more than once a year, and 12.8 million persons target shot more than once a year.43 Prevalence comparisons with other studies are of limited use owing to varying definitions and participant characteristics.
Exposure to recreational firearms presents a significant public health problem. Millions of men are at risk for incurring hearing damage from these firearms in the United States alone. Based on the patterns of the use of hearing protection in this study, this risk is not always taken seriously. There is a need for further education of users of recreational firearms regarding the risk of hearing impairment associated with firearm use and the availability and importance of appropriate hearing protection.
AUTHOR INFORMATION
Accepted for publication August 4, 1999.
This research was supported by grants R01 AG11099 (Dr Cruickshanks) and 2 U10 EY06594 (Drs Klein and Klein) from the National Institutes of Health, Bethesda, Md.
Presented in part at the 32nd Annual Meeting of the Society for Epidemiologic Research, Baltimore, Md, June 11, 1999.
| Editor's Note: Should we add questions on hunting and target shooting to standard patient questionnaires? Perhaps we should in communities where the likelihood of these activities is high, but not where the rate of these activities is low.—Marjorie A. Bowman, MD, MPA
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Corresponding author: David M. Nondahl, MS, Department of Ophthalmology and Visual Sciences, 610 N Walnut St, 460 WARF, Madison, WI 53705-2397 (e-mail: nondahl{at}epi.ophth.wisc.edu).
From the University of Wisconsin, Departments of Ophthalmology and Visual Sciences (Messrs Nondahl and Tweed and Drs Cruickshanks, Klein, and Klein), Preventive Medicine (Dr Cruickshanks), and Communicative Disorders (Dr Wiley and Mr Tweed), Madison.
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