Prevalence of hearing loss among Canadians aged 20 to 79: Audiometric results from the 2012/2013 Canadian Health Measures Survey

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by Katya Feder, David Michaud, Pamela Ramage-Morin, James McNamee and Yves Beauregard

Hearing loss is an important public health concern with far-reaching implications. At the beginning of the twenty-first century, the World Health Organization reported adult-onset hearing loss to be one of the leading causes of years lost due to disability (YLD); in 2001, hearing loss accounted for 4.7% of total YLD due to all causes, with the total global YLD for hearing loss estimated at 24.9 million years.^{Note 1,Note 2} As well, hearing loss has been associated with worse quality of life and functional outcomes.^Note 3 The personal consequences may include social isolation, depression, safety issues, mobility limitations, and reduced income and employment opportunities.^Note 4-6 Yet despite the importance of hearing for daily functioning, hearing loss is often unrecognized and undertreated. ^{Note 3,Note 7}

In Canada, the prevalence of hearing loss has typically been estimated through self-reports. For example, according to the Canada Community Health Survey and the Participation and Activity Limitations Survey, the self-reported prevalence of hearing impairment was 4% and 5% for the population aged 12 or older and 15 or older, respectively.^{Note 8,Note 9} However, self-reports may result in underestimates, especially among older adults and among people with mild hearing loss.^Note 10-13 Survey respondents may not self-identify as having a hearing disability and/or may not even be aware of it, particularly if it is mild or moderate.^{Note 14,Note 15} Furthermore, hearing loss occurs gradually and represents the lifetime cumulative insults to the auditory system,^{Note 16,Note 17} initially affecting the high frequencies and later progressing to lower frequencies that can affect speech comprehension. Age of onset varies, depending on factors such as genetic susceptibility, the presence of diseases, and exposure to drugs that are toxic to hearing.^{Note 16,Note 18,Note 19}

Objective measurement of hearing acuity is necessary to determine the extent of the problem.^Note 20 Clinical studies using audiometry have been carried out in specific populations and/or age groups, but no population-based audiometrically measured hearing data have been available for Canada.

The 2012/2013 Canadian Health Measures Survey (CHMS), a population-based survey designed to provide national estimates of health indicators, included both audiometric evaluation and self-reports. This study presents an analysis of CHMS audiometric and self-reported hearing data for adults aged 20 to 79. The study was approved by the Health Canada and Public Health Agency of Canada Review Ethics Board (Protocol #2005-0025).

Methods

Data source

The data are from the Canadian Health Measures Survey (CHMS), an ongoing cross-sectional survey that samples households in five regions across Canada (Atlantic, Quebec, Ontario, Prairies and British Columbia). The survey entails an in-person, computer-assisted household interview to gather demographic, socioeconomic, health and lifestyle information, and a subsequent visit to a mobile examination centre (MEC) for direct physical measures. The CHMS excludes full-time members of the Canadian Forces; residents of the three territories, First Nations Reserves and other Aboriginal settlements, and certain remote regions; and residents of institutions such as nursing homes. Together, these exclusions make up about 4% of the target population. Proxy interviews are accepted in cases of physical and/or intellectual impairment.

Details about sampling design, data collection and calculation of response rates are available elsewhere.^Note 21

Screening

To account for potential temporary threshold shift, CHMS respondents were asked if they had listened to loud noise/music in the previous 24 hours; 6.7% had done so, but no significant differences were found in four-frequency pure-tone average hearing loss between those who reported exposure to loud noise/music and those who did not.

Before testing, a visual inspection of the outer ear flap (pinna) and entrance to the ear canal was performed to identify signs of infection, obstruction and other conditions/circumstances that might interfere with testing.

Hearing evaluation

Otoscopy was performed using the Welch Allyn otoscope (Model 25020) to identify gross abnormalities, including the presence of blood, pus, excessive or impacted ear wax, a growth, tumor or foreign object in the ear canal, a collapsible ear canal, or other occlusion. The criteria for exclusion were: obstructed ear canal, acute pain or infection, open wounds or bandages covering the ear(s), refusal to remove hearing aid, and chronic ear conditions including congenital atresa or microtia of the ear canal (one or both ears). No further testing was performed if the individual was excluded by otoscopy.

Tympanometry was conducted using the A GSI 39 Auto Tympanometer. A normal tympanogram was compliance between 0.2 cm³ to 1.8 cm³ with middle ear pressure between -150 and +50 daPa in an equivalent ear canal volume of between 0.75 cm³ and 2.0 cm³. The criteriafor exclusion were: blood, pus or impacted wax, eardrum perforation, growth in the ear canal, and significant skin abnormality or discharge observed during otoscopy. In these cases, audiometry was performed using TDH-39 supra-aural headphones instead of insert earphones.

Audiometric evaluation was carried out by health measures specialists with training/supervision provided by a certified audiologist, which included on-site visits to ensure quality control. Testing was conducted in a portable audiometric booth (Eckel, AB-4230), using a computer- controlled CCA-100 mini audiometer with insert earphones (EAR 5A case) and disposable foam ear tips or supra-aural headphones (TDH-39). Hearing thresholds were assessed at 0.5, 1, 2, 3, 4, 6 and 8 kHz. Testing followed procedures recommended for standard audiometry using automatic mode, except when the respondent could not physically press the response button or had very slow response times, or when difficulties were noted with automatic mode. Manual mode was carried out using the modified down-10 up-5 methodology.^Note 22 The audiometer was calibrated daily using the Bio-Acoustic simulator BAS-200, which served as a baseline. To avoid interference with audiometric evaluation, subjects were asked to refrain from using chewing gum or candies. A Casella CEL-633 sound level meter monitored ambient sound pressure levels inside the sound booth. Testing was paused if sound pressure levels exceeded 55 dB for more than 2 seconds. Respondents who refused to sit in the audiometric booth with the door closed or who had cognitive deficits that interfered with testing were excluded from audiometric evaluation.

Self-reported hearing loss

To determine self-reported hearing loss, the Health Utilities Index Mark 3 (HUI3) hearing attribute was administered.^{Note 23,Note 24} HUI3 is a generic preference-based measure of functional health. Respondents were asked: “Are you usually able to hear what is said in a group conversation with at least three other people without a hearing aid?” Those who responded “no” were asked follow-up questions: “Are you usually able to hear what is said in a group conversation with at least three other people with a hearing aid?,” “Are you able to hear at all?,” “Are you usually able to hear what is said in a conversation with one other person in a quiet room without a hearing aid?,” and “Are you usually able to hear what is said in a conversation with one other person in a quiet room with a hearing aid?” Responses were scored according to an established algorithm and classified as level 1 (no hearing problems) to level 6 (unable to hear at all). A dichotomous variable identified individuals with hearing problems (levels 2 to 6) versus no hearing problems (level 1).

Definitions

Hearing loss was defined as a unilateral or bilateral hearing threshold above 25 dB in the worse ear, based on four-frequency pure-tone average (PTA) across 0.5, 1, 2 and 4 kHz (frequencies generally associated with normal speech), high-frequency PTA across 3, 4, 6, and 8 kHz, and low-frequency PTA across 0.5, 1 and 2 kHz. Unilateral and bilateral hearing loss were mutually exclusive. Hearing loss thresholds were based on the American Speech-Language Hearing Association guidelines^Note 25 (Text table 1).

Text table 1
Hearing loss categories and thresholds for people aged 20 to 79

Occlusion of ear canal indicates excessive earwax or pus observed during otoscopic examination.

Household education was defined as the highest level attained by a household member, dichotomized as less than postsecondary graduation and postsecondary graduation or more.

Based on total annual income, three household income categories were defined: less than $50,000; $50,000 to less than $100,000; and $100,000 or more.

Respondents’ age was as of the date of their MEC visit; education and income, as of the date of their household interview.

Study sample

The overall response rate for cycle 3 was 51.7%, yielding 5,785 respondents aged 3 to 79 who completed the household questionnaire and MEC visit. The study sample was established by excluding 2,601 respondents aged 19 or younger, and a further 212 with the following conditions: a) ear infection, cochlear implant (56); b) collapsed ear canal or complete obstruction of ear canal, pain/trauma to ear, ear surgery within previous three months, refusal to remove hearing aids or participate in otoscopy (33); or c) incomplete or unacceptable audiometric testing, including audiometry results for only one ear (123). The final study sample comprised 2,972 respondents aged 20 to 79 (1,483 men and 1,489 women) with bilateral audiometric results, representing 23.7 million Canadians.

Analytical techniques

Weighted frequencies and cross-tabulations were used to estimate measured and self-reported hearing levels by sex, age group, total household income, and highest household educational attainment. All estimates were weighted at the person level to represent the population. Analyses were conducted using SAS 9.1.3 and SAS-Callable SUDAAN 11.0.0 software. To account for the complex survey design, p-values, 95% confidence intervals, and coefficients of variation (CV) were estimated using the bootstrap technique with 11 degrees of freedom.^{Note 26,Note 27} In the tables and text, estimates with a CV of 16.6% to 33.3% are flagged with an E (interpret with caution); those with a CV that exceeds 33.3% are not releaseable and are designated F.

Results

In 2012/2013, an estimated 4.6 million Canadians aged 20 to 79 (19%) had hearing loss that affected their ability to hear normal speech (Table 1). That is, their audiometric tests revealed that their pure-tone average (PTA) across the four speech frequencies (0.5, 1, 2 and 4 kHz) was greater than 25 dB.

Table 1
Prevalence of measured four-frequency, low-frequency and high-frequency pure-tone average (PTA) hearing loss, by selected characteristics, household population aged 20 to 79, Canada excluding territories, 2012/2013

For 12% of Canadian adults, hearing loss was mild (26 dB to 40 dB) (Table 2). These people would be less likely to be aware of or self-report their hearing difficulty, and would cope by using adaptive measures such as moving closer to the source of the sound or increasing the volume.  For 7% of adults, hearing loss was moderate or worse (41 dB or above); these individuals would be more likely to notice and self-report hearing impairment.

Table 2
Percentage distribution of population, by measured hearing status in four-frequency and high-frequency pure-tone average ranges and age group, household population aged 20 to 79, Canada excluding territories, 2012/2013

Overall, a larger percentage of men than women had four-frequency hearing loss: 25% versus 13% (Table 1). However, the difference emerged around age 60 (data not shown).

The prevalence of hearing loss rose with advancing age. While no more than 10% of people younger than age 50 had four-frequency hearing loss, the percentage was 65% among  70- to 79-year-olds.

Income and education were associated with hearing loss. The likelihood of having four-frequency hearing loss was 28% among people in households where annual income was less than $50,000, compared with 12% among those in households where annual income was $100,000 or more. Adults in households with lower levels of education were almost twice as likely as those in households where one or more members was a postsecondary graduate to have a hearing loss: 30% versus 16%.

Hearing loss measured over low (0.5, 1 and 2 kHz) and high (3, 4, 6 and 8 kHz) frequencies generally followed the same patterns as four-frequency hearing loss. However, high-frequency hearing loss was more common than four-frequency hearing loss—35% (8.4 million) versus 19% (4.6 million) of adults.

As well, people with high-frequency hearing loss were more likely to have hearing loss in both ears than in one ear (data not shown). For those with four-frequency hearing loss, the percentages with bilateral and unilateral loss were almost equal, while among those with low-frequency hearing loss, unilateral loss was more common.

The prevalence of measured hearing loss (19%) far surpassed the percentage of adults who reported difficulties hearing, based on the HUI (fewer than 4%) (Table 3). No difference between men and women was apparent in self-reported hearing difficulties, whereas the audiometric findings indicated that hearing loss was more prevalent among men.

Table 3
Prevalence of self-reported hearing difficulty, by selected characteristics, household population aged 20 to 79, Canada excluding territories, 2012/2013

Overall, 12%%^E of adults with measured hearing loss used a hearing aid (data not shown). At ages 60 to 69, 9%^E of those with hearing loss wore hearing aids; at ages 70 to 79, the figure was 24%^E. An estimated 25% of all moderately/severely impaired individuals used a hearing aid.

Otoscopy revealed that 13% of Canadian adults had occluding wax or pus (one or both ears), which likely affected their hearing acuity (data not shown). The prevalence of earwax rose from 11%^E among 20- to 39-year-olds to 21% among people aged 70 to 79.

Discussion

This is the first population-based study to report audiometric data for Canadians. According to results of the 2012/2013 CHMS, 19% of people aged 20 to 79 (4.6 million) had at least mild hearing loss in frequencies that are important for understanding speech. This far exceeded the percentage who self-reported hearing difficulties—fewer than 4%.

This disparity between measured hearing loss and self-reported difficulties was consistent with previous findings.^Note 11-14 However, the discrepancy in the CHMS data was wider than what was observed in studies that used a single question (“Do you feel you have a hearing loss?”), the Hearing Handicap Inventory for the Elderly-Screening (HHIE-S) tool, or questions about increased television volume.^{Note 11,Note 12,Note 28,Note 29}  The wide disparities in the present study may be due to the hearing questions that comprise the HUI3 or to differing demographic distributions across studies. The low self-reported prevalence in all studies may reflect the insidious nature of hearing loss and the tendency for individuals to unknowingly compensate and/or blame background noise for hearing difficulties, especially in cases of mild or high-frequency hearing loss.

Comparisons of Canadian audiometric estimates with those of population-based studies conducted in the United States,^{Note 10,Note 30} Great Britain^Note 31 and Australia^Note 32 reveal consistent trends (Text table 2). Discrepancies between CHMS estimates and those of other surveys that used  audiometric measures may be due to participant characteristics such as the presence of earwax or the use of medications that affect hearing.

Text table 2
Population-based studies: Prevalence of hearing loss above 25 dB (averaged over 0.5, 1, 2, 4 kHz), by age group, Canada, United States, Great Britain and Austrialia, selected years

The male-female gap in the prevalence of hearing loss starting around age 60 in the CHMS data is fairly consistent with global patterns, except that in other populations, the disparity emerged at younger ages.^Note 31-34 The differences may reflect the relatively small CHMS sample (2,972) compared with other population-based studies, some of which used several years of data. Additional audiometric data from future CHMS cycles may yield greater consistency with global trends.  The higher prevalence of hearing loss among men has been partly attributed to their greater likelihood of being exposed to loud noise at work or during leisure-time activities.^Note 35

The present study shows increasing bilateral hearing loss at older ages—the percentage rose sharply in middle age, and nearly doubled by ages 70 to 79. The effect of aging on hearing acuity is indisputable, but many factors influence the degree and rate of deterioration, including  genetic susceptibility, ototoxic medication exposure, otological disorders, smoking, and occupational and leisure noise exposure ^{Note 7,Note 16,Note 18,Note 30,Note 36-40} In addition, an interaction between early noise exposure and acceleration of hearing loss has been postulated, with evidence that the aging process is different in noise-damaged cochlea (inner ear), compared with unaffected cochlea.^Note 41 Further studies are warranted to investigate factors related to hearing loss that were outside the scope of this analysis.

The elevated prevalence of high-frequency loss among older Canadians is in line with research showing that age-related hearing loss begins in the highest test frequencies.^Note 17 High-frequency hearing loss impairs the ability to detect higher-pitched sounds (for example, doorbell, telephone ringing, kettle whistling in another room) and consonants such as s and f. This type of hearing loss affects understanding of speech in noisy or reverberant environments^Note 17 and makes it difficult to distinguish between certain words (sun/fun, sight/fight, bike/kite). Progression toward lower speech frequencies (2 to 4 kHz) that are important for hearing voiceless consonants (t,p,k,s,ch) would affect hearing some words (fish, cat, sit tip) and the ability to understand speech in any situation.^Note 17 Also noteworthy is the impact of hearing loss on individuals communicating in their non-native language, for whom even a mild loss is problematic.^Note 42

This analysis revealed a higher prevalence of hearing loss among adults with lower household income and education. These results are similar to Swedish^Note 36 and Australian^Note 32 findings, and are consistent with the association between lower socioeconomic status and poor health outcomes in general. Difficulties that lower socioeconomic groups encounter in accessing health care and treatment^{Note 43,Note 44} may result in conditions that can affect hearing.

A minority—12%—of hearing-impaired Canadians used hearing aids. Even at older ages, the percentage was relatively small: 24%^E of 70- to 79-year-olds with four-frequency hearing loss wore a hearing aid. This was similar to NHANES findings (19%) for Americans aged 70 or older.^Note 10

Reasons for the low rate of hearing aid use are beyond the scope of this study, but the health care systems in different nations may be a factor. Mizutari et al.^Note 45 reported lower hearing aid ownership/use (7.3%) in Japan where hearing aids are not covered, compared with countries where hearing aids are available through public health insurance (United Kingdom, France, Denmark, Netherlands) or are provided with restrictions (Australia).^{Note 46,Note 47} In Canada, hearing aid subsidies and eligibility vary by province.^Note 48 According to Gopinath et al.,^Note 38 the reasons most commonly cited by older adults for not obtaining a hearing aid were the cost and the belief that it was not needed. A smaller study in Norway (where hearing aids are covered by public health insurance) found “acknowledgement of need for hearing aids” and “checkups/accessibility to professionals” accounted for 25% and 24%, respectively, of the variance in hearing aid use. The findings of the present study would be enhanced by information on the frequency of hearing aid use, associations with income and cost, and whether hearing aids improved functional communication.

Occluding earwax, which may reduce hearing acuity, was found in 13% of adults—double to six times the rate reported in other population-based studies.^{Note 31,Note 34} The prevalence of earwax was 21% among 70- to 79-year-old CHMS participants, somewhat below percentages reported in previous analyses of older adults.^{Note 49,Note 50} Other research found that earwax removal improved audiometric hearing thresholds for 40% to 75% of older participants.^{Note 33,Note 49}

Limitations

The results of this analysis should be interpreted in the context of several limitations.

The sample size is small, and the data are cross-sectional. The findings offer a snapshot of the hearing status of Canadians in 2012/2013, but no information about the progression of hearing loss over time is available.

Moreover, the prevalence of hearing loss may be underestimated. The CHMS data pertain to the population aged 20 to 79, and so exclude people aged 80 or older, ages at which hearing loss is common. As well, people with complete ear canal obstruction and those with incomplete audiometry or those among whom only one ear was tested were excluded.

In addition, the CHMS excludes residents of institutions such as nursing homes, a large percentage of whom would be affected by hearing loss. The other groups not covered by the survey—full-time member of the Canadian Forces, and residents of the three territories, First Nations Reserves or other Aboriginal settlements, and certain remote regions—would have less impact on the hearing loss estimates.

It was not possible to distinguish between conductive and sensorineural hearing loss in this study, as bone conduction testing was not performed.

Although validated for measuring functional health, the HUI3 tool (self-reported hearing difficulty questions) was not specifically validated in studies involving hearing-impaired respondents and controls.

Finally, analysis using both “worse ear” and “better ear” definitions of hearing loss would have yielded additional information and facilitated comparisons with more studies.

Conclusion

Results of the 2012/2013 CHMS show that about one in five Canadians aged 20 to 79, an estimated 4.6 million adults, had audiometrically measured hearing loss. The large disparity between measured and self-reported prevalence in this study suggests that hearing loss is often unrecognized. Measured hearing loss rose sharply after age 40, to reach 65% at ages 70 to 79. The numbers affected are likely to rise substantially in coming decades. The population aged 65 or older, the age range most likely to have hearing loss, is projected to double from 5 million in 2011 to 10.4 million by 2036.^Note 51