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Home , Audiometry, Deafness, Hearing loss, Otology, Presbycusis

Global burden of loss in the year 2000

Colin Mathers1, Andrew Smith2, Marisol Concha3

1. Introduction Hearing impairment is the most frequent sensory deficit in human populations, affecting more than 250 million people in the world. Consequences of hearing impairment include inability to interpret speech sounds, often producing a reduced ability to communicate, delay in acquisition, economic and educational disadvantage, and stigmatisation. It may be worsened by some medical conditions such as , diabetes, and possibly hyperlipidemia, among others. Most congenital and childhood onset is included as sequelae to various and causes already included in the Global Burden of Disease Study. Examples include media, memingitis, , congenital anomalies and non-syndromal inherited hearing loss. Adult-onset hearing loss was not separately analysed in the original Global Burden of Disease for 1990 (1). The leading causes of adult-onset hearing loss are (age related hearing loss) followed by -induced hearing loss. This paper reviews global data on hearing loss among children and among adults, and estimates the global burden of adult-onset hearing loss. In addition, it provides estimates of the prevalence of hearing loss among children and adults at various levels of severity. In the Version 1 estimates for the Global Burden of Disease 2000 study, published in the World Report 2001 (2), adult-onset hearing loss was the 2nd leading cause of YLDs at global level, accounting for 4.6% of total global YLDs. This paper summarises the data and methods used to produce the Version 3 estimates of adult-onset hearing loss burden for the year 2000, as published in the World Health Report 2003.

2. Case and sequelae definitions There is a diversity of definitions of hearing impairment, thus, comparison among studies is difficult. We use WHO classification that classified hearing impairment according to the pure tone average in the better hearing . Categories of hearing impairment ranges from “no impairment” to “profound impairment” according the threshold level. The hearing threshold level, using , is to be taken as the better ear average for four frequencies 0.5, 1, 2, and 4 kHz. (3) The different grades of hearing impairment and their impact in performance are presented in Table 2.1. Duivestijn (4) discusses the effect of different definitions on measured prevalence of hearing loss.

1 Epidemiology and Burden of Disease, WHO Geneva (GPE/EBD) 2 Prevention of Blindness and (MNC/PBD), WHO Geneva 3 Ministry of Health, Chile

1 Global Burden of Disease 2000 Table 2.2 summarizes the GBD 2000 case and sequelae definitions for adult-onset hearing loss. For the GBD 2000, the burden of adult-onset hearing loss has been estimated for moderate or greater hearing impairment. While the prevalence of slight impairment (26-40dBHL) has also been estimated, it has been assumed to have negligible weight and not to contribute to the YLD for hearing loss. Table 2.1 WHO grades of hearing impairment

Audiometric ISO value (average of 500, 1000, 2000, Grade of Impairment 4000 Hz) Impairment description 0 (no impairment) 25 dBHL or less (better ear) No or very slight hearing problems. Able to hear whispers 1 (Slight impairment) 26-40 dBHL (better ear) Able to hear and repeat words spoken in normal voice at 1 metre 2 (Moderate impairment) 41-60 dBHL (better ear) Able to hear and repeat words using raised voice at 1 metre 3 (severe impairment) 61-80 dBHL (better ear) Able to hear some words when shouted into better ear 4 (Profound impairment 81 dBHL or greater (better ear) Unable to hear and understand even a shouted including deafness) voice

Source: (3)

Table 2.2 GBD 2000 case and severity-level definitions for adult-onset hearing loss

Cause category GBD 2000 Code ICD 9 codes ICD 10 codes Adult-onset hearing loss U102 389 H90-H91

Severity level Definition Hearing loss, adult onset Cases of adult onset hearing loss due to or noise exposure. Excludes hearing loss due to congenital causes, infectious , other diseases or injury. Moderate hearing loss Hearing threshold level in the better ear is 41-60 dBHTL (averaged over 0.5, 1, 2, 4kHz). (Not able to hear and repeat words spoken in normal voice at 1 metre). Person may or may not use a Severe hearing loss Hearing threshold level in the better ear is 61-80 dBHTL (averaged over 0.5, 1, 2, 4kHz). (Not able to hear and repeat words using raised voice at 1 metre). Person may or may not use a hearing aid Profound hearing loss Hearing threshold level in the better ear is 81 dBHTL or more (averaged over 0.5, 1, 2, 4kHz). (Not able to hear words when shouted into better ear). Person may or may not use a hearing aid

3. Population prevalence and incidence studies In spite of the number of published studies about hearing impairment (HI), the currently available data is mostly incomplete and use different criteria, which causes difficulties in comparison and estimation of the problem. Also, only relatively few studies have been carried out to date in representative population samples. Table 3.1 shows the prevalence of hearing impairment measured

2 Global Burden of Disease 2000 by in countries with available information. Population-based surveys conducted in several developing countries have used the protocols developed by WHO to identify causes of HI and prevalence. Available data on hearing loss prevalence in children are summarized in Table 3.2.

3 Global Burden of Disease 2000 Table 3.1. Prevalence studies for hearing impairment: adults

Study Sample Prevalences Country population Ref. Years Definition used size Age range available by

UK Four cities (5,6) 1980-86 25+, 45+, 65+ dBHL in 2,910 17-80 Age, sex better ear Italy Milan, Padua, (7) 1989 25+, 45+, 65+, 90+ dBHL 2,170 18+ Age Florence, Bari, in the better ear Palermo Denmark Copenhagen - (8) 1976 25+dBHL in better ear 300 49-69 Age males 0.5,1,2,4) Denmark Jutland (rural) (9) Early 25+ dBHL 1,397 31-50 Age x sex 1990s 35+ dBHL 45+ dBHL, Finland Northern (10) 1997 21+, 40+, 70+, 95+ dBHL 5,400 5-75 Age Ostrobothnia in the better ear (0.5,1,2,4) USA Framingham (11) 1979 25+ dBHL (0.5,1,2,4 2,293 57-89 kHz) in better ear USA Beaver Dam, (12- 1993-95 26+, 41+, >60 in WORSE 3,753 48-92 Age x sex (26+ Wisconsin 14) ear (0.5,1,2,4 kHz ) only) >25 dBHL in better ear (0.5,1,2,4) USA Beaver Dam, (15- 1987-88 26+, 41+, >60 in WORSE 48-92 Wisconsin 16) ear (0.5,1,2,4 kHz ) USA NHANES 1 (17- 1971-75 25+ dBHL in the better 2,506 55-74 Age x sex national 18) ear (HFPTA scale 1,2,4 kHz) USA HHANES (19) 1982-84 26+, 41+ in WORSE ear 2,751 20-74 Age x sex Hispanic (0.5,1,2 kHz ) Americans Brazil Residents of the (20) 2003 26+,41+, 61+, 81+ dBHL 3,858 All ages Age, sex city of Canoas, or, better ear RS, Brazil Australia South Australia (21) 1996? 25+, 35+, 45+, 65+ dBHL 9,027 15+ Age x sex in better ear 0.5,1,2,4) Oman National (22) 1996-97 26+, 41+ dBHL (1,2,3 11,402 All ages Age kHz bilateral/better ear) India Vellore, Taluk, (23- 1997-98 26+,41+, 61+, 81+ dBHL 5,432 All ages Age Tamil Nadu 24) or, better ear India Lucknow rural (25) 1975-76 15+, 30+, 60+ dBHL, 904 All ages Age x sex (15+) bilateral deafness and Age (30+,60+) unilateral deafness India Lucknow urban (26) 1970 15+, 30+, 60+ dBHL, 904 All ages Age x sex (15+) bilateral deafness and Age (30+,60+) unilateral deafness Sri Lanka Kandy district (23- 1998- 27+, 41+, 61+ 81+ dBHL, 4,858 All ages Age (41+ only) 24) 2000? better ear (1,2,4 kHz bilateral/better ear)

4 Global Burden of Disease 2000 Nepal Two regions (27) 1990? 31, 51+, 81+ dBHL, 15,845 5+ years Age better ear (1,2,4 kHz bilateral/better ear) China Sichuan (28- 1986-87 27+, 56+, 91+ dBHL, 126,876 All ages Age, sex 29) better ear (27+ only) Korea Community- (30) 1994-97 27+, 41+, 56+, 71+ 39,004 25+ Age x sex based and dBHL, both ; Age (56, 71) health clinics presbycusis only

5 Global Burden of Disease 2000 Table 3.1 (continued). Prevalence studies for hearing impairment: adults

Thailand 17 provinces (31) 1988-90 41 dBHL, better ear 7,499 All ages Thailand Bangkok + 5 (31) 1986-87 41+, 61+, 81+ dBHL, 1,797 All ages Total only provinces better ear (0.5, 1, 2 kHz bilateral/better ear) Indonesia Bandung (23- 1997-98 26+, 41+, 61+ 81+ dBHL, 5,604 All ages Age (41+ only) municipality & 24) (1,2,4 kHz bilateral/better district ear) Myanmar Yangon (23- 1997-98 26+, 41+, 61+ 81+ dBHL, 5,604 All ages Age (41+ only) 24) (1,2,4 kHz bilateral/better ear) Vietnam 6 selected (32) 26+, 41+, 61+ 81+ dBHL, 13,120 6 months Age x sex provinces (3 (1,2,4 kHz bilateral/better and older north, 3 south) ear) Nigeria 3 states: Akua (33) 2000- 26+, 41+, 61+ 81+ dBHL, 8,975 All ages Age (41+ only) Ibom, Benue, 2001 (1,2,4 kHz bilateral/better Katsina ear)

Standardized prevalence of adult-onset hearing loss Prevalence studies use different thresholds (and in some cases different definitions in terms of frequencies and better or worse ear) and different age groups. Where non-WHO thresholds used, the prevalence of hearing impairment at the WHO thresholds was interpolated assuming the log of the cumulative prevalence is linear with threshold. This relationship holds reasonably well in most studies. Where prevalences were not available by sex, the sex ratio from a similar study in the same region was assumed. Prevalences were estimated for GBD age groups and the WHO hearing impairment thresholds. Table 3.3 summarizes these estimates showing age-standardized prevalences for ages 15 and over. Prevalence of adult onset hearing loss was estimated by subtracting from prevalences at ages 20 and over, the estimated prevalence of hearing loss for teenage children (15-19 years) or the nearest similar age group for which prevalences available. It is assumed that the incidence of adult-onset hearing loss associated with and other infectious and non-infectious causes included elsewhere in the GBD 2000 cause list is negligible compared to the incidence of adult-onset hearing loss associated with age-related hearing degeneration or noise-induced loss. The estimated prevalence of hearing loss for teenage children is summarized in Table 3.4. Figures 3.1 and 3.2 summarize the estimated age-standardized prevalences of adult-onset hearing loss at 41+ dBHTL and 61+ dBHTL respectively for the studies listed in Table 3.3. Figure 3.3 shows the range of male/female prevalence ratios for these studies.

6 Global Burden of Disease 2000 Table 3.2 Prevalence studies for hearing impairment: children

Prevalence Study Sample Country population Ref. Years Definition used size Age range % Developed Review (34) Review 41+ dBHL better ear Childhood 0.05 – 0.23 UK Trent region (35) 1985-1993 40+ dBHL better ear at 552,558 0-9 0.133 birth 0.5, 1, 2, 4 kHz prevalence4 USA Atlanta (36) 1991-93 40+ dBHL better ear at 255,742 3-10 0.11 0.5, 1, 2 kHz USA NHANES II (37) 1982-1984 31+ dB HL better ear 7,888 6-19 and Hispanic African-Am. 0.78 HANES Cuban Am. 1.21 Mexican Am. 0.60 0.38 White, non-H. USA NHANES III (38) 1988-94 16+, 26+ dB HL at 0.5, 6,166 6-19 0.7 (16+) 1, 2 kHz better ear 0.4 (26+) Developing Review (34) Review 41+ dBHL better ear Childhood 0.2-0.42 Thailand Bangkok (31) ? 41+ dBHL better ear 10,242 School age 3.9 schools 2,153 Children 6.1 Rural schools Sierra Leone Panguma (39) 1992 26+, 41+, 61+ dBHL 2,015 5-15 2.58 (26-40) better ear 0.65 (41-60) 0.50 (61+) Angola Luanda (40) 1992? 31+ dBHL better ear at 1,030 Schoolchildren 2.0 .5, 1, 2 kHz Zimbabwe (41) 1970s 31+ dBHL better ear 885 Schoolchildren 3.3 Kenya Kiambu (42) 1990? 31+ dBHL better ear at 5,368 Primary 2.2 district 2 & 4 kHz school age Tanzania Northern (43) 31+ dBHL either ear at 854 Primary 3.0 inland district .5, 1, 2 kHz school age Severe/profound 0.35 South Poor rural (44) 1990? 21+, 31+, 41+ dBHL 401 6-13 2.0 (31+) Africa district in better ear 0.5 (41+) Western Cape Swaziland 1st year (44) school- children Saudi Riyadh (45) 1997 20+dBHL, Air cond at 6421 2m – 12y 7.7 Arabia .25-.8kHz & .5-4kHz bone cond, unilateral or better ear bilateral

4 This figure refers to what the authors call “permanent childhood hearing impairment”– that is sensorineural hearing loss and includes 16% who had post-natally acquired loss. The prevalence rate for congenital hearing impairments was 0.112%. The figures are not directly comparable with data from the WHO studies which include conductive loss.

7 Global Burden of Disease 2000 Table 3.3. Estimated prevalences of adult onset hearing loss for adults aged 15 years and over

Age standardized prevalence (%) Male/Females prevalence ratio 26+ 41+ 61+ 81+ 26+ 41+ 61+ 81+ UK (1) 11.8 4.0 1.1 0.3 1.2 1.1 1.0 0.9 Italy (2) 12.7 4.4 1.3 1.3 1.2 1.1 1.0 1.0 Denmark (3) 12.8 3.5 0.8 0.1 1.9 2.3 1.5 0.8 Finland (4) 7.4 2.3 0.5 0.2 1.4 1.5 1.1 0.9 Australia 11.8 2.6 0.4 0.1 1.9 2.4 1.3 0.7 USA NHANES1 (5) 11.5 3.4 0.8 0.1 1.7 1.6 1.0 0.5 BeaverDam (6) 8.7 2.5 0.6 0.1 2.2 1.6 1.0 0.5 Hispanic (7) 10.0 3.0 0.7 0.1 2.1 1.6 1.0 0.5

China (1) 4.0 2.8 1.3 0.3 1.0 1.0 1.0 1.0 Korea (8) 15.5 2.8 0.3 0.2 1.3 1.5 1.1 1.0 India Vellore (1) 7.6 4.4 2.5 0.8 1.1 1.0 1.0 Vellore 2 (1) 8.0 1.5 0.1 1.0 1.0 1.0 Lucknow Urban (9) 9.8 6.2 3.1 1.5 1.1 1.2 1.0 1.0 Lucknow Rural (9) 7.3 5.6 3.5 2.3 1.0 1.0 1.0 1.0 Nepal (10) 15.3 8.7 4.5 2.5 1.2 1.4 1.4 1.0 Oman (11) 11.2 6.2 3.0 1.5 1.1 1.1 Indonesia (1) 7.1 1.4 0.1 1.5 1.0 1.0 Myanmar (1) 8.6 2.7 0.0 1.2 1.0 1.0 SriLanka (1) 21.7 10.0 3.4 0.5 1.3 1.3 1.0 1.0 Thailand (12) 11.6 2.9 0.9 1.3 1.1 1.1 Nigeria (1) 4.5 1.1

Notes:

(1) Overall sex ratio at each threshold assumed to apply for each age group.

(2) Odds ratio for measured and self-reported hearing loss by sex 1.0; but around 2 for noise exposure which is greater in manual occupations - so possibly a male excess. UK sex ratios used as proxy.

(3) Prevalences for missing age groups estimated using Finnish and Australian age patterns.

(4) Danish sex ratios used for age groups 30-50.

(5) Prevalences extrapolated to all ages 15+ using UK age patterns and sex ratio of 1.56. Prevalence ratio of 26+/41+ assumed to be the same as in the Beaver Dam study.

(6) Prevalences extrapolated to all ages 15+ using Australian age patterns.

(7) Prevalence estimates based on sample-weighted average of prevalences for Mexican and Cuban born Americans. Prevalence of hearing impairment in better ear estimated using ratio for better ear to worse ear from Beaver Dam study. Prevalence adjusted for exclusion of 4kHz frequency using data from the Framingham study.

(8) Chinese aetiology data from Liu et al. found that presbyacusis was 54% of non-infectious causes. Reported prevalences for presbyacusis adjusted upwards accordingly.

(9) Assumed same proportion bilateral as in rural study: For 15+ dBHTL, 74.3% had bilateral deafness. Unilateral tended to be mild deafness. In the rural study, for unilateral deafness, 96% mild-moderate, while 90% for those with bilateral deafness

(10) Assumed same sex ratios as in India.

(11) Prevalences adjusted for difference in prevalence for 1,2,3 and 0.5,1,2,4 kHz using data from Duijvestijn et al 1999

(12) No age distributions given in Thai study. Age pattern based on average for 4 SEARO countries (Sri Lanka, India, Indonesia, Myanmar).

8 Global Burden of Disease 2000

9 Global Burden of Disease 2000 Table 3.4: Estimated prevalences childhood onset hearing loss at ages 15-19

15+ 26+ 31+ 41+ 61+ 81+

UK 1.00 0.13 0.10 0.10 Italy 1.00 0.13 0.10 0.10 Denmark 1.00 0.10 0.10 Finland 1.00 0.20 0.10 AUS 1.00 0.10 0.10 USA NHANES1 1.00 0.13 0.10 BeaverDam 1.00 0.13 0.10 Hispanic 1.50 0.50

China 1.00 0.15 0.12 0.10 Korea India (Vellore) 2.00 0.00 India (Vellore 2) 1.58 0.10 0.08 India (Lucknow 11.50 3.31 1.57 0.22 Urban) India (Lucknow 13.10 4.57 2.43 0.35 Rural Nepal 5.57 2.96 2.00 1.00 0.61 OMAN 3.33 0.66 0.10 Indonesia 0.80 0.10 0.08 Myanmar 3.82 0.10 0.05 SriLanka 3.53 0.10 0.10 Thailand 5.40 0.15 0.00 Nigeria 9.3 6.86 3.02 0.93 0.58

10 Global Burden of Disease 2000

UK

Italy

Denmark

Finland

AUS

USA NHANES1

BeaverDam

Hispanic

China

Korea

India (Vellore)

India (Vellore 2)

India (Lucknow Urban)

India (Lucknow Rural

Nepal

OMAN

Indonesia

Myanmar

SriLanka

Thailand

Nigeria

0 2 4 6 8 10 12 14 Age-standardised prevalence (%) at 41+ dBHLT

Figure 3.1. Estimated age-standardised adult-onset hearing loss prevalence rates, 41+ dBHTL, available population studies.

11 Global Burden of Disease 2000

UK

Italy

Denmark

Finland

AUS

USA NHANES1

BeaverDam

Hispanic

China

Korea

India (Vellore)

India (Vellore 2)

India (Lucknow Urban)

India (Lucknow Rural

Nepal

Indonesia

Myanmar

SriLanka

Thailand

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Age-standardised prevalence (%) at 61+ dBHLT

Figure 3.2. Estimated age-standardised adult-onset hearing loss prevalence rates, 61+ dBHTL, available population studies.

12 Global Burden of Disease 2000 UK Italy Finland BeaverDam

Hispanic USA NHANES1 Denmark AUS China

China India (Lucknow Rural India (Lucknow Urban) India (Vellore 2)

India (Vellore) OMAN Myanmar SriLanka Thailand

Nepal Indonesia Korea Nigeria

0 0.5 1 1.5 2 2.5

Male/female ratio at 41+ dBHTL

Figure 3.3. Estimated male/female ratio of age-standardised adult-onset hearing loss prevalence rates, 41+ dBHTL, available population studies.

4. Disease model for adult-onset hearing loss The incidence and average duration of moderate or greater hearing loss (41+ dBHTL as defined in Table 2.2) were estimated for each GBD 2000 epidemiological region from estimates of prevalence by age and sex using the software program DISMOD II, assuming zero remission rate and a relative risk of mortality of 1. There is conflicting evidence between mortality and hearing loss. In a ten year longitudinal analysis of the NHANES I participants aged 55-74 years at baseline who received hearing examination found than hearing loss predicts mortality: RR = 1.17 (46), however other studies have reported that after controlling by age the association disappear. We assume an RR of 1.0.

13 Global Burden of Disease 2000

Incidence of HI Prevalence Death

Years lived with disability (YLDs) were calculated for the boxes shaded in grey.

Figure 4.1 Adult-onset hearing loss disease model.

Available treatment includes hearing aids, cochlear implants, and reading. Cochlear implants5 are used by people with severe and profound hearing impairments who obtain negligible benefit from hearing aids. While cochlear implants result in remission from hearing loss, the use of these is negligible at the population level, and we assume a remission rate of zero. The effect of hearing aid use is modelled as a reduction in the severity of hearing loss, and hence a lower disability weight. YLD for hearing loss are calculated from estimated incidence, average duration and disability weight (1). Disability weights for hearing loss used in the GBD 1990 study (1) and the Netherlands disability weights study (47) are shown in Table 4.1. The Australian Burden of Disease study (48) used modified Dutch weights together with Australian survey information on severity distribution in the population. The resulting average disability weight is shown in the last column of Table 4.1. Table 4.1 Disability weights for adult-onset hearing loss

Stage/sequela GBD 1990 Netherlands Study Australian Study Mild hearing loss 0.04 0.02 Moderate hearing loss 0.12 0.12 Severe hearing loss 0.333 (indicator 0.37 0.37 (deafness) condition) All levels 0.216 (untreated) 0.168 (treated)

The global coverage of hearing aid use has been estimated to be no more than 10%, skewed towards developed countries (49). Less than 1% of hearing impaired individuals use hearing aids in developing countries, while in developed countries the rate ranges from 10% to 40% (see Section 5 below). It is thus important to take into account the average prevalence of hearing aid use by region in calculating the average disability weight for hearing loss. Little information is available on the impact of hearing aid use on hearing disability. We provisionally assume that hearing aid use reduces the disability weight to the next lower severity level as shown in Table 4.2. While we give zero

5 It is a device designed to provide sound detection and improved speech understanding

14 Global Burden of Disease 2000 disability weight to untreated mild hearing loss, we give a residual weight of 0.04 (the Dutch weight for mild hearing loss) to a person with moderate hearing loss who uses a hearing aid. These provisional weights will be revised following analysis of the health state valuation data collected in the World Health Survey in 2002-2003. Table 4.2 Provisional disability weights for adult-onset hearing loss, GBD 2000 (Version 2)

Disability Stage/sequela weight Comment Mild (26-40 dBHTL) untreated 0.00 Moderate (41-60 dBHTL) untreated 0.12 Dutch weight for moderate hearing loss Severe and profound hearing loss GBD weight for deafness as indicator condition (61+ dBHTL) untreated 0.333 (Dutch weight is 0.37)

Dutch weight for mild hearing loss (25-44 Moderate (41-60 dBHTL) with hearing aid 0.04 dBHTL) Severe and profound hearing loss Dutch weight for moderate hearing loss (45-64 (61+ dBHTL) with hearing aid 0.12 dBHTL)

5. Treatment for hearing impairment Studies measuring prevalence of hearing aid use were reviewed (5,15,16,19,21,48,50-69) and used to estimate the prevalence of hearing aid use among individuals with hearing impairment (assuming that hearing aid use is confined to moderate impairment levels and greater. The results are shown in Table 5.2 below.

Table 5.2 Estimated regional prevalence of hearing aid use among those with hearing loss, by severity level, age and sex, GBD 2000 (Version 3)

Severity Other (dBHTL) AMRO A AMRO B AMRO D EURO A EURO B1 EUR B2 EUR C WPRA regions 41-60 Male 15-29 5 0 0 5 5 0 0 0 0 30-44 10 0 0 5 5 0 0 20 0 45-59 20 3 3 10 10 3 3 30 0 60-69 20 3 3 10 10 3 3 30 0 70-79 20 3 3 10 10 3 3 30 0 Female 15-29 5 0 0 5 5 0 0 5 0 30-44 10 0 0 5 5 0 0 10 0 45-59 20 3 3 10 10 3 3 20 0

15 Global Burden of Disease 2000 60-69 20 3 3 20 20 3 3 20 0 70-79 20 3 3 30 30 3 3 20 0

61-80 Male 15+ 50 10 10 50 50 10 10 75 0 Female 15+ 50 10 10 50 50 10 10 50 0

81+ Male 15+ 80 25 25 80 80 25 80 80 0 Female 15+ 80 25 25 80 80 25 80 80 0

16 Global Burden of Disease 2000 Age-sex-region specific estimates of prevalence of hearing loss at each of the severity levels (see Section 6 below) were combined with the estimated prevalence of hearing aid use (Table 5.2) to compute average disability weights by age, sex and region for hearing loss at levels 41 dBHTL and higher. The average disability weights thus vary by age and sex across regions. The resulting average disability weights are summarized below in Table 5.3.

Table 5.3 Estimated average disability weight for ages 15+, by subregion and sex

Subregion Male Female Subregion Male Female AFRO D 0.19 0.20 EURO B2 0.17 0.17 AFRO E 0.19 0.20 EURO C 0.16 0.16 AMRO A 0.13 0.14 SEARO B 0.15 0.17 AMRO B 0.15 0.17 SEARO D 0.16 0.16 AMRO D 0.15 0.17 WPRO A 0.11 0.14 EMRO B 0.18 0.18 WPRO B1 0.19 0.19 EMRO D 0.18 0.18 WPRO B2 0.17 0.19 EURO A 0.13 0.13 WPRO B3 0.17 0.19 EURO B1 0.13 0.13

6. Regional incidence and prevalence estimates Tables 6.1 and 6.2 summarise the data and assumptions used to estimate regional prevalence rates for children and adults. For those regions with no available hearing loss prevalence studies, prevalence rates were assumed to be similar to other selected regions.

Table 6.1 Data and assumptions used to estimate regional prevalence rates for child-onset hearing loss

AFRO D and E From Nigeria study. Prevalences for 26+ dB assumed similar to SEARO D AMRO A Based on prevalences estimated for WPRO A and NHANES III data AMRO B and D Based on prevalences estimated for WPRO A, NHANES III and HHANES EMRO B and D Prevalences from Oman study. For 81+ dB, assume similar to other regions EURO A Based on study prevalences, plus other studies of congenital deafness and childhood deafness EURO B1 and C Assumed the same as Euro A EURO B2 Based on average of prevalences for Euro B1 and Emro B SEARO B Average for India, Indonesia and Vietnam. Prevalences for 26+ dBHTL based on application of India ratios 26+/41+to average for 41+ from the three studies SEARO D Based on India (Vellore 2). Prevalences for 26+ dBHTL based on average of India (urban) and India (rural) ratios of 26+/41+ applied to 41+ prevalences WPRO A Based on Australian study WPRO B1 Weighted average of China, Korea and Vietnam data. Inclusion of Vietnam to represent southern and rural areas of China.

17 Global Burden of Disease 2000 WPRO B2 Based on average of Indonesia, Myanmar, Vietnam and India. As Indonesia and Myanmar have very high prevalences, conservative estimates were made giving these lower weight in the average. Prevalences for 26+ dBHTL based on application of India ratios 26+/41+ to 41+ prevalences WPRO B3 No information. Have used an average of WPRO B1/B2 and SEARO B/D plus (0.5) weighted AFRO.

18 Global Burden of Disease 2000 Table 6.2 Data and assumptions used to estimate regional prevalence rates for adults

AFRO D and E Based on Nigerian study AMRO A Based on NHANES (using information also from Beaver Dam) AMRO B and D Based on Hispanic HANES EMRO B and D Based on Oman EURO A Population-weighted average of prevalences for Britain, Italy, Denmark and Finland EURO B1 and C Assumed the same as Euro A EURO B2 Based on average of prevalences for Euro B1 and Emro B SEARO B Average for India, Indonesia and Vietnam. Prevalences for 26+ dBHTL based on application of India ratios 26+/41+to average for 41+ from the three studies SEARO D Based on India (Vellore 2). Prevalences for 26+ dBHTL based on average of India (urban) and India (rural) ratios of 26+/41+ applied to 41+ prevalences WPRO A Based on Australian study WPRO B1 Weighted average of China, Korea and Vietnam data. Inclusion of Vietnam to represent southern and rural areas of China. WPRO B2 Based on average of Indonesia, Myanmar, Vietnam and India. As Indonesia and Myanmar have very high prevalences, conservative estimates were made giving these lower weight in the average. Prevalences for 26+ dBHTL based on application of India ratios 26+/41+ to 41+ prevalences WPRO B3 No information. Have used an average of WPRO B1/B2 and SEARO B/D plus (0.5) weighted AFRO.

The resulting overall global prevalences of hearing loss at various threshold levels are shown below in Table 6.3. There are an estimated 588 million persons (including children) with mild or greater hearing loss globally, an estimated 248 million with moderate or greater hearing loss, and 53 million with severe or profound hearing loss. Figure 6.1 shows the resulting regional prevalences for moderate or greater hearing loss and the age-specific prevalence rates by regional groupings.

Table 6.3 Estimated global prevalence of hearing loss, GBD 2000 (Version 2)

Severity (dBHTL) Males Females Persons Miild or greater (26+) Adult-onset 215 197 413 Child-onset 89 86 175

Total 304 284 588 Moderate or greater (41+) Adult-onset 94 93 187 Child-onset 31 31 61

Total 125 123 248 Severe or greater (61+) Adult-onset 21 25 46

19 Global Burden of Disease 2000 Child-onset 3 3 7

Total 24 29 53

Profound (81+) Adult-onset 3 5 8 Child-onset 3 3 6 Total 6 8 14

20 Global Burden of Disease 2000 Prevalence - Males Prevalence - Females

AFRO D - 1 AFRO D - 1

AFRO E - 2 AFRO E - 2

AMRO A - 3 AMRO A - 3

AMRO B - 4 AMRO B - 4

AMRO D - 5 AMRO D - 5

EMRO B - 6 EMRO B - 6

EMRO D - 7 EMRO D - 7

EURO A - 8 EURO A - 8

EURO B1 - 9 EURO B1 - 9

EURO B2 -10 EURO B2 -10

EURO C -11 EURO C -11

SEARO B -12 SEARO B -12

SEARO D -13 SEARO D -13

WPRO A -14 WPRO A -14

WPRO B1-15 WPRO B1-15

WPRO B2-16 WPRO B2-16

WPRO B3-17 WPRO B3-17

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000

Age-std prevalence/100,000 Age-std prevalence/100,000

70000 60000 A Regions A Regions Males Females AMRO BD AMRO BD 60000 50000 EURO BC EURO BC EMRO EMRO 50000 SEARO SEARO 40000 WPRO B WPRO B 40000 AFRO AFRO

30000 30000 Prevalence/100,000 Prevalence/100,000 20000 20000

10000 10000

0 0 0-4 5-14 15-29 30-44 45-59 60-69 70-79 80+ 0-4 5-14 15-29 30-44 45-59 60-69 70-79 80+ Age groups Age groups

Figure 6.1. Estimated adult-onset hearing loss prevalence rates, 41+ dBHTL, by region and sex, GBD 2000 Version 2.

21 Global Burden of Disease 2000

Table 6.3. Adult-onset hearing loss (41+ dBHTL): age-standardized incidence and prevalence estimates for WHO epidemiological subregions, 2000.

Age-std. Incidence/100,000 Age-std. prevalence/100,000

Subregion Males Females Males Females

AFRO D 213.8 167.8 3466.8 2919.3 AFRO E 203.9 169.2 3451.1 2976.7 AMRO A 323.1 189.0 4351.5 2643.0 AMRO B 264.7 150.1 3500.9 2119.8 AMRO D 260.3 150.8 3498.1 2107.9 EMRO B 324.2 281.3 4829.5 4200.5 EMRO D 322.8 279.1 4829.0 4241.4 EURO A 234.9 190.0 3337.6 2795.5 EURO B1 233.8 189.7 3301.7 2803.7 EURO B2 273.0 228.9 4037.9 3557.5 EURO C 274.8 235.0 4078.6 3561.7 SEARO B 421.8 336.7 6390.3 4901.9 SEARO D 363.2 360.0 5870.1 5827.1 WPRO A 243.1 187.7 2859.6 2685.9 WPRO B1 159.5 127.4 2567.5 2056.6 WPRO B2 430.7 346.4 6352.3 4506.2 WPRO B3 326.8 278.1 5081.0 4163.0

World 271.5 220.1 4036.3 3326.7

· Age-standardized to World Standard Population.

22 Global Burden of Disease 2000 7. Global burden of adult-onset hearing loss in 2000 General methods used for the estimation of the global burden of disease are given elsewhere (50). The tables and graphs below summarise the global burden of adult-onset hearing loss estimates for the GBD 2000. Total global YLD for hearing loss are estimated to be 24.9 million or 4.7% of total YLD due to all causes. This makes hearing loss the second leading cause of YLD after , and gives it a larger non-fatal burden than alcohol use disorders, osteoarthritis and schizophrenia.

Table 7.1. Adult-onset hearing loss: YLD, YLL and DALY estimates by subregion, 2000.

YLD/100,000 YLL/100,000 YLD YLL DALY

Subregion Males Females Males Females (‘000) (‘000) (‘000)

AFRO D 304.2 299.8 0.0 0.0 1,008 0 1,008 AFRO E 301.6 285.6 0.0 0.0 991 0 991 AMRO A 475.1 357.4 0.0 0.0 1,286 0 1,286 AMRO B 277.7 222.7 0.0 0.0 1,106 0 1,106 AMRO D 221.4 171.4 0.0 0.0 140 0 140 EMRO B 409.5 358.1 0.0 0.0 537 0 537 EMRO D 383.0 399.5 0.0 0.0 540 0 540 EURO A 450.9 434.3 0.0 0.0 1,818 0 1,818 EURO B1 328.6 334.3 0.0 0.0 550 0 550 EURO B2 352.8 383.4 0.0 0.0 188 0 188 EURO C 479.0 550.8 0.0 0.0 1,271 0 1,271 SEARO B 570.0 453.7 0.0 0.0 2,019 0 2,019 SEARO D 514.4 551.3 0.0 0.0 7,177 0 7,177 WPRO A 337.0 451.6 0.0 0.0 591 0 591 WPRO B1 386.9 352.2 0.0 0.0 5,025 0 5,025 WPRO B2 479.7 427.9 0.0 0.0 644 0 644 WPRO B3 394.4 346.7 0.0 0.0 25 0 25

World 420.5 403.7 0.0 0.0 24,915 0 24,915

8. Conclusions These are version 3 estimates for the GBD 2000 as published in the World Health Report 2003. Apart from uncertainty analysis, updating estimates to reflect revisions of mortality estimates and any new or revised epidemiological data or evidence, it is not intended to undertake any major addition revision of these estimates. We welcome comments and criticisms of these draft estimates, and information on additional sources of data and evidence.

23 Global Burden of Disease 2000 Acknowledgements We particularly wish to thank Christina Bernard and Jennifer Wong for assistance with literature reviews, DISMOD analyses and preparation of this paper.

24 Global Burden of Disease 2000

MALES - YLD per 1,000

World

MEC - EMRO B+D GBD 2000 GBD 1990 LAC - AMRO B+D

SSA - AFRO D+E

OAI - SEARB+WPRB2/3

CHI - WPRO B1

IND - SEARO D

FSE - Euro B+C

EME - A regions

0.00 1.00 2.00 3.00 4.00 5.00 6.00 YLD/1000

FEMALES - YLD per 1,000

World GBD 2000 MEC - EMRO B+D GBD 1990 LAC - AMRO B+D

SSA - AFRO D+E

OAI - SEARB+WPRB2/3

CHI - WPRO B1

IND - SEARO D

FSE - Euro B+C

EME - A regions

0.00 1.00 2.00 3.00 4.00 5.00 6.00 YLD/1000

Figure 7.1. Adult-onset hearing loss YLD rates, by sex, broad regions, 1990 and 2000.

25 Global Burden of Disease 2000 MALES - Global YLD per 1,000 by age 14.00

GBD 1990 12.00 GBD 2000 10.00

8.00

6.00 YLD/1000

4.00

2.00

0.00 0 20 40 60 80 100

FEMALES - Global YLD per 1,000 by age 14.00 GBD 1990 12.00 GBD 2000 10.00

8.00

6.00 YLD/1000

4.00

2.00

0.00 0 20 40 60 80 100

Figure 7.2. Global adult-onset hearing loss YLD rates, by age and sex, 1990 and 2000.

26 Global Burden of Disease 2000 References

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