Global Burden Of Hearing Loss In The Year 2000

Global burden of hearing loss in the year 2000 Colin Mathers1, Andrew Smith 2, 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 language acquisition, economic and educational disadvantage, social isolation and stigmatisation. It may be worsened by some medical conditions such as hypothyroidism, diabetes, and possibly hyperlipidemia, among others. Most congenital and childhood onset hearing loss is included as sequelae to various disease and injury causes already included in the Global Burden of Disease Study. Examples include otitis media, memingitis, rubella, 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 presbycusis (age related hearing loss) followed by noise-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 Health 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 ear. Categories of hearing impairment ranges from “no impairment” to “profound impairment” according the threshold level. The hearing threshold level, using audiometry, 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 Deafness (MNC/PBD), WHO Geneva 3 Ministry of Health, Chile

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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 disability weight and not to contribute to the YLD for hearing loss. Table 2.1 WHO grades of hearing impairment

Grade of Impairment

Audiometric ISO value (average of 500, 1000, 2000, 4000 Hz)

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

Impairment description

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 including deafness)

81 dBHL or greater (better ear) Unable to hear and understand even a shouted 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 ageing or noise exposure. Excludes hearing loss due to congenital causes, infectious diseases, 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 hearing aid

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 pure tone audiometry 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.

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Global Burden of Disease 2000

Table 3.1. Prevalence studies for hearing impairment: adults Country

Study population

UK

Four cities

Italy

Milan, Padua, Florence, Bari, Palermo

Denmark Denmark

Ref.

Sample Prevalences size Age range available by

Years

Definition used

1980-86

25+, 45+, 65+ dBHL in better ear

2,910

17-80

Age, sex

(7)

1989

25+, 45+, 65+, 90+ dBHL in the better ear

2,170

18+

Age

Copenhagen males

(8)

1976

25+dBHL in better ear 0.5,1,2,4)

300

49-69

Age

Jutland (rural)

(9)

Early 1990s

25+ dBHL

1,397

31-50

Age x sex

Age

(5,6)

35+ dBHL 45+ dBHL,

Finland

Northern Ostrobothnia

(10)

1997

21+, 40+, 70+, 95+ dBHL in the better ear (0.5,1,2,4)

5,400

5-75

USA

Framingham

(11)

1979

25+ dBHL (0.5,1,2,4 kHz) in better ear

2,293

57-89

USA

Beaver Dam, Wisconsin

(1214)

1993-95

26+, 41+, >60 in WORSE ear (0.5,1,2,4 kHz )

3,753

48-92

Age x sex (26+ only)

>25 dBHL in better ear (0.5,1,2,4) USA

Beaver Dam, Wisconsin

(1516)

1987-88

26+, 41+, >60 in WORSE ear (0.5,1,2,4 kHz )

USA

NHANES 1 national

(1718)

1971-75

25+ dBHL in the better ear (HFPTA scale 1,2,4 kHz)

2,506

55-74

Age x sex

USA

HHANES Hispanic Americans

(19)

1982-84

26+, 41+ in WORSE ear (0.5,1,2 kHz )

2,751

20-74

Age x sex

Brazil

Residents of the city of Canoas, RS, Brazil

(20)

2003

26+,41+, 61+, 81+ dBHL or, better ear

3,858

All ages

Age, sex

Australia

South Australia

(21)

1996?

25+, 35+, 45+, 65+ dBHL in better ear

9,027

15+

Age x sex

11,402

All ages

Age

5,432

All ages

Age

48-92

0.5,1,2,4) Oman

National

(22)

1996-97

26+, 41+ dBHL (1,2,3 kHz bilateral/better ear)

India

Vellore, Taluk, Tamil Nadu

(2324)

1997-98

26+,41+, 61+, 81+ dBHL or, better ear

India

Lucknow rural

(25)

1975-76

15+, 30+, 60+ dBHL, bilateral deafness and unilateral deafness

904

All ages

Age x sex (15+) Age (30+,60+)

India

Lucknow urban

(26)

1970

15+, 30+, 60+ dBHL, bilateral deafness and unilateral deafness

904

All ages

Age x sex (15+) Age (30+,60+)

Sri Lanka

Kandy district

(2324)

19982000?

27+, 41+, 61+ 81+ dBHL, better ear (1,2,4 kHz bilateral/better ear)

4,858

All ages

Age (41+ only)

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Global Burden of Disease 2000

Nepal

Two regions

(27)

1990?

31, 51+, 81+ dBHL, better ear (1,2,4 kHz bilateral/better ear)

15,845

5+ years

Age

China

Sichuan

(2829)

1986-87

27+, 56+, 91+ dBHL, better ear

126,876

All ages

Age, sex (27+ only)

Korea

Communitybased and health clinics

(30)

1994-97

27+, 41+, 56+, 71+ dBHL, both ears; presbycusis only

25+

Age x sex Age (56, 71)

5

39,004

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 provinces

(31)

1986-87

41+, 61+, 81+ dBHL, better ear (0.5, 1, 2 kHz bilateral/better ear)

1,797

All ages

Total only

Indonesia

Bandung municipality & district

(2324)

1997-98

26+, 41+, 61+ 81+ dBHL, (1,2,4 kHz bilateral/better ear)

5,604

All ages

Age (41+ only)

Myanmar

Yangon

(2324)

1997-98

26+, 41+, 61+ 81+ dBHL, (1,2,4 kHz bilateral/better ear)

5,604

All ages

Age (41+ only)

Vietnam

6 selected provinces (3 north, 3 south)

(32)

26+, 41+, 61+ 81+ dBHL, (1,2,4 kHz bilateral/better ear)

13,120

6 months and older

Age x sex

Nigeria

3 states: Akua Ibom, Benue, Katsina

(33)

26+, 41+, 61+ 81+ dBHL, (1,2,4 kHz bilateral/better ear)

8,975

All ages

Age (41+ only)

20002001

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 otitis media 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.

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Global Burden of Disease 2000

Table 3.2 Prevalence studies for hearing impairment: children

Country

Study population

Ref.

Years

Definition used

Sample size

Prevalence Age range

%

Childhood

0.05 – 0.23

Developed

Review

(34)

Review

41+ dBHL better ear

UK

Trent region

(35)

1985-1993

40+ dBHL better ear at 0.5, 1, 2, 4 kHz

552,558

0-9

0.133 birth prevalence4

USA

Atlanta

(36)

1991-93

40+ dBHL better ear at 0.5, 1, 2 kHz

255,742

3-10

0.11

USA

NHANES II and Hispanic HANES

(37)

1982-1984

31+ dB HL better ear

7,888

6-19 African-Am. Cuban Am. Mexican Am. White, non-H.

USA

NHANES III

(38)

Developing

Review

(34)

Review

41+ dBHL better ear

Thailand

Bangkok schools Rural schools

(31)

?

41+ dBHL better ear

Sierra Leone

Panguma

(39)

1992

Angola

Luanda

(40)

Zimbabwe

6-19

0.7 (16+) 0.4 (26+)

Childhood

0.2-0.42

10,242 2,153

School age Children

3.9 6.1

26+, 41+, 61+ dBHL better ear

2,015

5-15

1992?

31+ dBHL better ear at .5, 1, 2 kHz

1,030

Schoolchildren

2.0

(41)

1970s

31+ dBHL better ear

885

Schoolchildren

3.3

1990?

31+ dBHL better ear at 2 & 4 kHz

5,368

Primary school age

2.2

31+ dBHL either ear at .5, 1, 2 kHz

854

Primary school age

3.0

Kenya

Kiambu district

(42)

Tanzania

Northern inland district

(43)

1988-94

16+, 26+ dB HL at 0.5, 1, 2 kHz better ear

6,166

0.78 1.21 0.60 0.38

Severe/profound South Africa

Poor rural district in Western Cape

(44)

Swaziland

1st year schoolchildren

(44)

Saudi Arabia

Riyadh

(45)

2.58 (26-40) 0.65 (41-60) 0.50 (61+)

0.35

1990?

21+, 31+, 41+ dBHL better ear

401

6-13

1997

20+dBHL, Air cond at .25-.8kHz & .5-4kHz bone cond, unilateral or better ear bilateral

6421

2m – 12y

2.0 (31+) 0.5 (41+)

7.7

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

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

8.7

2.5

0.6

0.1

2.2

1.6

1.0

0.5

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

7.6

4.4

2.5

0.8

1.1

1.0

1.0

8.0

1.5

0.1

1.0

1.0

1.0

9.8

6.2

3.1

1.5

1.1

1.2

1.0

1.0

Finland (4)

BeaverDam (6) Hispanic (7)

India Vellore (1) Vellore 2 (1) Lucknow Urban (9)

7.3

5.6

3.5

2.3

1.0

1.0

1.0

1.0

Nepal (10)

Lucknow Rural (9)

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

10.0

3.4

0.5

1.3

1.0

1.0

11.6

2.9

0.9

1.3

1.1

1.1

SriLanka (1)

21.7

Thailand (12) Nigeria (1)

4.5

1.3

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 exclus ion 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).

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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

India (Vellore)

2.00

0.00

India (Vellore 2)

1.58

0.10

0.10

Korea

India (Lucknow Urban)

11.50

3.31

1.57

0.22

India (Lucknow Rural

13.10

4.57

2.43

0.35

Nepal

5.57

2.96

OMAN

3.33

0.08

2.00

1.00

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

3.02

0.93

0.58

Nigeria

9.3

6.86

10

0.61

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 Age-standardised prevalence (%) at 41+ dBHLT

12

14

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 Age-standardised prevalence (%) at 61+ dBHLT

4.5

5

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 lip 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

0.37

0.37

Severe hearing loss (deafness)

0.333 (indicator 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) Stage/sequela

Disability weight

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 (61+ dBHTL) untreated

0.333

GBD weight for deafness as indicator condition (Dutch weight is 0.37)

Moderate (41-60 dBHTL) with hearing aid

0.04

Dutch weight for mild hearing loss (25-44 dBHTL)

Severe and profound hearing loss (61+ dBHTL) with hearing aid

0.12

Dutch weight for moderate hearing loss (45-64 dBHTL)

Comment

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 (dBHTL) 41-60

AMRO A

AMRO B AMRO D EURO A EURO B1 EUR B2 EUR C

WPRA

Other regions

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

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

Male

Female

15

Global Burden of Disease 2000

61-80

81+

60-69

20

3

3

20

20

3

3

20

0

70-79

20

3

3

30

30

3

3

20

0

Male 15+

50

10

10

50

50

10

10

75

0

Female 15+ 50

10

10

50

50

10

10

50

0

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 sam e 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

304

284

588

Adult-onset

94

93

187

Child-onset

31

31

61

125

123

248

21

25

46

Total Moderate or greater (41+)

Total Severe or greater (61+) Adult-onset

19

Global Burden of Disease 2000

Child-onset

3

3

7

24

29

53

Adult-onset

3

5

8

Child-onset

3

3

6

Total

6

8

14

Total Profound (81+)

20

Global Burden of Disease 2000

Prevalence - Females

Prevalence - Males 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

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

60000

70000 A Regions

A Regions

Males 50000

EURO BC

EURO BC EMRO

EMRO 50000

SEARO

SEARO

40000 Prevalence/100,000

WPRO B AFRO

40000

Females

AMRO BD

AMRO BD

60000

Prevalence/100,000

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

30000

WPRO B AFRO

30000

20000

20000

10000

10000

0 0-4

5-14

15-29 30-44 45-59 60-69 70-79

0

80+

0-4

Age groups

5-14 15-29 30-44 45-59 60-69 70-79

80+

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 Subregion

Males

Females

Age-std. prevalence/100,000 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 depression, 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 Subregion

YLL/100,000

YLD

YLL

(‘000)

(‘000)

DALY

Males

Females

Males

Females

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

434.3

0.0

0.0

1,818

0

1,818

0

550

EURO A

450.9

(‘000)

EURO B1

328.6

334.3

0.0

0.0

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

427.9

0.0

0.0

644

0

644

0

25

0

24,915

WPRO B2

479.7

WPRO B3

394.4

346.7

0.0

0.0

25

World

420.5

403.7

0.0

0.0

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

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 YLD/1000

4.00

5.00

6.00

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

YLD/1000

10.00 8.00 6.00 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

YLD/1000

10.00 8.00 6.00 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

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