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3. PREVALENCE OF IODINE DEFICIENCY DISORDERS (IDD)


3.1 EUROPEAN REGION
3.2 AMERICAN REGION
3.3 AFRICAN REGION
3.4 SOUTHEAST ASIAN REGION
3.5 WESTERN PACIFIC REGION
3.6 GENERAL CONCLUSIONS

In the 1960 WHO monograph, Kelly and Snedden estimated a population of 200 million in the world to be suffering from goitre (Clements et al., 1960 p.28). More recent estimates exceed this figure in spite of extensive iodization programmes. The worldwide distribution of Iodine Deficiency Disorders (IDD) in developing countries is shown in Fig. 1 in "Introduction and Policy Implications" Section.

There is consensus that some 800 million people are at risk of IDD from living in iodine-deficient environments, with 190 million suffering from goitre and more than 3 million with overt cretinism, while millions more suffer from some intellectual deficit (Hetzel, 1987 p.7).

In the Southeast Asia Region eight countries - Bangladesh, Bhutan, Burma, India, Indonesia, Nepal, Sri Lanka and Thailand - all have significant IDD problems. Altogether in these eight countries, it has been estimated in the light of extensive surveys that 277 million are at risk of IDD, some 102 million have goitre, 1.5 million are cretins, and many more suffer from some degree of mental or motor impairment as a result of iodine deficiency (Clugston and Bagchi, 1985).

In the People's Republic of China, it has been estimated that some 300 million are living in iodine-deficient regions and therefore exposed to the risk of IDD. Only one-third of this population was reported as adequately covered by control programmes in 1982 (Ma et al., 1982)1. Fever data are available from Africa, but the indications are that the IDD problem is widespread (see Section 3.3). In Latin America the problem persists in Bolivia, Peru, Ecuador and many other countries, in spite of attempts to control IDD with iodized salt (WHO, 1984). IDD persist in many European countries including Germany (both F.R.G. and G.D.R.), Romania, Poland, Spain, Portugal and Italy (European Thyroid Association, 1985).

1More recent information (Ma and Li, 1987) indicates coverage expanding to 87% of the deficient population.
Detailed information from the major regions follows. Individual country programmes are considered in Section 6.

3.1 EUROPEAN REGION

The report of the Subcommittee on Goitre and Iodine Deficiency in Europe of the European Thyroid Association (ETA) makes the following comment: "The Scientific Community of the ETA has the obligation to contribute to the eradication of endemic goitre and iodine deficiency in Europe. With the available knowledge it seems an anachronism that endemic goitre in Europe still prevails (European Thyroid Association, 1985). The report goes on to note the lack of information. The available data were confined largely to local areas. The report was nevertheless made because even with these limitations the data were "alarming enough".

The data are summarized in Table 6. Available information is confined to goitre prevalence, urinary iodine excretion surveys and prophylactic measures. The report notes, however, that assay of TSH in neonatal screening programmes is "a sensitive parameter for iodine deficiency".

TABLE 6

COUNTRIES (BY REGION) WHERE IODINE DEFICIENCY DISORDERS ARE
SIGNIFICANT HEALTH PROBLEM

REGION

CATEGORY A

CATEGORY B

CATEGORY C


Situation analysis made, national programme under way

Situation analysis made, or partially made. National programme not under way (pilot studies only)

Situation analysis made, probability based on indirect evidence, no programme

Europe(l)

Austria;+Belgium(V);



Bulgaria; *FRG(V);



Finland; France; *GDR;



+Greece(V); Hungary;



Ireland(V); +Italy(V);



+Netherlands; Norway(V);



*Poland; + Portugal(V);



*Romania(?); +Spain(V);

* Goitre - national problem


Sweden; Switzerland;

+ Goitre - local problem


+Turkey; USSR; Yugoslavia

V Voluntary programme

Africa(2)

Kenya, Mali,

Burkina Faso,



Mozambique,

Cameroon, Cote



Tanzania

d'Ivoire, Ethiopia,




Lesotho, Nigeria,




Senegal, Sierra




Leone, Zambia




Zimbabwe Iraq,


Southeast Asia(3)

Bangladesh, Bhutan, Nepal

Burman, India,



Indonesia

Sri Lanka



Thailand



Western Pacific(4)

China

Philippines

Kampuchea, Laos,




Malaysia, Vietnam

Eastern Med.(5)


Iran,

Afghanistan



Pakistan, Sudan


(1) From European Thyroid Association, 1985
(2) Goitre Control in the African Region, WHO, 1984
(3) Clugston and Bagchi, 1985
(4) Personal observations by T. Ma and C.H. Thilly
(5) Personal report by M. Benmiloud
Some data on neonatal levels of serum T-4 and TSH in Greece have been reported (Beckers et al., 1981) and are shown in Table 7. The table indicates a lowered level of serum T-4 and raised TSH in the endemic area where there is moderate iodine deficiency without clinical endemic cretinism. Urinary iodine levels are in the range of 13.4 -33.9 mcg/d.

TABLE 7

NEONATAL THYROID FUNCTION IN GREECE


No.

T-4 (mcg %)

SD

TSH (mcgU/ml)

SD

Endemic area, full term

54

8.8

4.8

15.37

8.20

Non-endemic area, full term

73

10.0

2.9

11.93

4.99

Athens, full term

98

10.3

3.3

10.96

6.33

Source: Beckers et al., 1981
The report notes that "there are some countries where endemic goitre is still prevalent when the country is regarded as a whole". This applies, for instance, to the Federal Republic of Germany and the German Democratic Republic.

In other countries - Spain, Portugal, Prance, Italy, Greece, Romania, Turkey, Poland and Yugoslavia - regional goitrous areas are well documented. This may also apply to Belgium, Denmark, Great Britain, Ireland and the Soviet Union. Further epidemiological studies are strongly recommended for some of these countries.

The report notes the large sums of money spent for the diagnosis and treatment of thyroid diseases in Europe, e.g. DM 308m for outpatient diagnosis and medical treatment of thyroid disorders in the Federal Republic of Germany in 1979. This money is mainly for the surgical expenses because of goitre and its complications. There is therefore a cost benefit to be gained from effective iodization programmes.

Conclusion

The persistence of the IDD problem in Europe, a continent of generally rich countries, is remarkable when control measures are readily available and affordable. There should be no further delay in setting up programmes aimed at eradicating them.

3.2 AMERICAN REGION

A recent report (Noguera et al., 1983, revised in 1984) notes that "Iodine deficiency and endemic goitre are still a problem in many countries in Latin America. In Bolivia, Ecuador and Peru cretinism is a frequent syndrome associated with higher prevalences of endemic goitre". It goes on to note that while there are legal provisions for the iodization of salt, these are not adequately carried out. There is also a need for educational programmes. A tabulation of detailed data on goitre prevalence and urinary iodine levels for all countries in Central and South America is provided in the report and is reproduced in Table 8. Further data are available in the recent PAHO/WHO monograph from the meeting in Lima, Peru (Dunn et al., 1986).

Conclusion

The tabulations indicate persistence of goitre in school children at a prevalence of over 10 percent in all countries with the exception of Costa Rica, Cuba and Uruguay. Urinary iodine levels are in the range 25 - 90 mcg/g of creatinine. A more effective iodization programme is clearly needed in all these countries.

TABLE 8

STUDIES ON ENDEMIC GOITRE PREVALENCE IN LATIN AMERICA (PAHO)

Country (year)

Type of population Studied

Population sampled

Size of sample

Method of goitre classification

Overall prevalence

Argentina

1967

Sch/children

Departmental

4,431

Perez & Scrimshaw

49.8






(12.5-61.9)

1967

20 years

Departmental

47,679

Perez & Scrimshaw

15.6






(4.3-53.6)

Bolivia

1976

Sch/children

La Paz

4,200

WHO modified

68

1979

Sch/children

Pando

680

WHO modified

77

1981

Sch/children

National

38,500

WHO adapted

60.8

Observation: WHO classification adjusted locally

Brazil

1966

Sch/children

45 municips.

45,924


27.2

1967

Sch/children

41 municips.

48,443


21.9

1975

Sch/children

National

266,373

WHO adapted*

14.7

Observation: *Only the inspection criterion was considered

Chile

1972

General

Community

8,407

Perez & Scrimshaw

24.8

Colombia

1945

Sch/children

National

183,243

Old classification

53

Observation: 385 municipalities examined

1945

Sch/children

Departmental

8,062

Old classification

83.1

Observation: 8 municipalities examined

1952

Sch/children

Departmental

6,511

Old classification

33.9

1965

Sch/children

Departmental

12,166

Old classification

1.8

Observation: In 1952 and 1965 the same municipal!tes were examined

Costa Rica

1966

General

National

4,065

Perez & Scrimshaw

18.0

1979

Sch/children

National

5,061

Perez & Scrimshaw

3.5

Cuba

1974

6-20 years

Baracoa

2,664

Perez & Scrimshaw

30.0

1976

General

Habana

6,149

Perez & Scrimshaw

3.4

Ecuador

1969

Sch/children

National

28,639

Perez & Scrimshaw

23.7

1978

Sch/children

National

36,962

Perez & Scrimshaw

12.0

Observation: In 1969 and 1978 the same localities were examined.

El Salvador

1966

General

National

3,231

Perez & Scrimshaw

48.0

Guatemala

1949

General

National

4,113

Old Classification

38.0

1965

General

National

2,995

Perez & Scrimshaw (Original)

5.2

1979

Sch/children

National

3,654

Perez & Scrimshaw

10.5

Honduras

1966

General

National

3,654

Perez & Scrimshaw

17.0

Mexico

1950

General

8 states

1,000,000


54.6

Nicaragua

1966

General

National

3,477

Perez & Scrimshaw

32.0

1977

General

National

13,814

Perez & Scrimshaw

33.0

1981

General

National

6,252

Perez & Scrimshaw

20.0

Panama

1967

General

National

3,071

Perez & Scrimshaw

16.5

1975

General

National

4,084

Perez & Scrimshaw

6.0

Paraguay

1976

General

National

4,078

Perez & Scrimshaw

18.1

1980

Maternal/ child

3 communities

343

WHO modified

23.6

1982

Sch/children

6 communities

420

WHO modified

16.40

Peru

1968

Sch/children

National

181,118

Perez & Scrimshaw

22.0

1976

General

National

9,293

WHO modified

15.0*

Observation: *Average prevalence in mountains, jungle and coast

Uruguay

1973

Sch/Children

Departmental

2,515

Perez & Scrimshaw

9.0

1980

Sch/Children

Departmental

1,245

Perez & Scrimshaw

2.0

Venezuela

1966

Sch/Children

National

470,207

Perez & Scrimshaw

13.0

1981

Sch/children






& adolescents

National

14,709

WHO modified

21.37

Source: Noguera et al., 1984
Note: Municips. = Municipalities

3.3 AFRICAN REGION

An extensive report (WHO, 1984) provides a valuable survey (see Table 6). The situation is summarized as follows (see also Table 9).

1. Goitre. Practically all countries of the region have significant goitrous areas and in some of them the problem is severe, e.g. 85 percent of female children aged 11-15 years in East Cameroon had palpable goitres of grades 1 to 3 (see Table 9).

2. Control is relatively easy from the technological viewpoint, by

a) iodized salt;
b) injecting iodized oil (every five years).
The strategy proposed by the WHO Africa Regional Office is to iodate salt where feasible within the country, preferably at national or provincial level, and (simultaneously or afterwards) deal with the remaining pockets by injections of iodized oil.

For most countries what is lacking is the political will, backing, and financial resources for the necessary intersectoral action, since the Implementation of such a programme necessitates at least the cooperation of the Ministries of Health, Trade and Commerce, Finance and sometimes other specialized bodies (laboratories for quality control of iodated salt, etc.).

More detailed data from Algeria, Zaire and Senegal have recently been published (Benmiloud and Ermans, 1986). The roles of retinol deficiency in Senegal and cassava consumption in Zaire have been identified as exacerbating the effects of iodine-deficiency. The fragmentary nature of the data from east, central and southern Africa has been pointed out (Volde-Gebriel, 1986).

Difficulties in Tanzania mentioned by Kavishe et al. (1981) include defining the magnitude of the problem, lack of laboratory facilities, the technology and organization of salt iodization at sector level, manpower and staff training. Recent data are given by Ekpechi (1987).

It seems likely that there is a high prevalence of goitre throughout the extensive southern Africa plateau which includes large areas of Zimbabwe, Zambia, Botswana and Mozambique, all of which have substantial IDD problems. In Zimbabwe, cretinism has been seen only in the more remote eastern highlands, justifying overall classification of the IDD problem as moderate.

TABLE 9

PREVALENCE OF ENDEMIC GOITRE IN SELECTED AREAS OF AFRICA

Country


Palpable goitres grades 1-3 (%)(1)

Visible goitres grades 2-3 (%)(1)

Cameroon





East Cameroon:





Adults:


M 48

F 70.7

-

Children:

11-15 yrs.

M 61.5

F 85.1

(grade 3) 1.3-12


5-17 yrs.

M 51-85

F 59-92


West Cameroon:





Children:

5-17 yrs.

M 40-58

F 37-70


Ethiopia





ICNND 1959 (2)





Molineaux -

Gondar

M 10-14

F 30-39

4-12





47





90

Hofvander

Ijaji



27


Bako



53

Ethiopia Nutrition




Institute (1978)





Bora


53

28


Ankober


71

48


Ebantu


28

5


Bure


67

37

Cote d'lvoire





9 subprefectures





0-7 yrs.

M 66

F 7.1

-


8-15 yrs.

M 11.9

F 12.9

-


16-25 yrs.

M 4.2

F 15.9

-


25

M 9.3(32)

F 32.1

-

(1) See Section 7 for definition of grades
(2) ICNND - Interdepartmental Committee on Nutrition
M = Male
F = Female for National Defence (USA)

Country

Palpable goitres grades 1-3 (%)

Visible goitres grades 2-3 (%)

Kenya


Eburu Naivasha


(Rift Valley)

M 41

F 60

M 18

F 39

Roret (Kericho)

M 40

F 58

M 16

F 32

Lesotho (1957-58)





M 30-50




(41)



(1-12 years)



M 7

F 9

(13-18 years)



M 14

F 22

(above 18 years)



M 23

P 15

Mali




Pales 1948

10.2%



Hellegouarch 1968:




Boubouni

F 24-41

M 13.25


Bandiagara

F 43-69

M 30-63


Ag Rhaly




1974 Icati, Dio, Neguela

42-97



1975 quartier Samakebougou (Kati)

F 53

M 48


1976 Neguela

F 67

M 53


1978 Neguela-Koulikoro (Ile Region)

48-72



Nigeria




1966 Nwokolo, Ekpeche & Nvokolo Nsukka

F 14-59

M 15-20


Ogoja

P 10-81

M 26-58


1965 Nutrition Survey,




Nigeria




Lagos (children)

F 11



Savannah (5-15 yrs.)

F 15



Plateau (5-15 yrs.)

F 10



Jos/Pankshin (5-llyrs)

F 16

M 14


Asaba (5-11 years)

F 42



Olurin 1970-74




Oyo

12-32



Ashoun

15-50



Ijesha

18-32



Ekiti

20-37



Afemai

16-20



Senegal




Children




6-12 years:

M 32

F 41


13-18 years:

M 26

F 36

Casamance




F 11 - 48




Eastern Senegal




F 23 - 51

Adults

M 18

F 50


Sierra Leone




South-Eastern Province




Kono

56



Koinadugu-Koranko

M 43

F 71

-

Kenema, Kalhun

M 19

F 25

-

Lowlands

0


-

Burkina Faso (all ages)

7.7 (0-18% Didougou)

-

Zambia

M 42

F 59

M 8

F 19

Source: Goitre Control in the African Region. WHO, 1984
Conclusion

In general, only fragmentary data are available for Africa and technical resources are severely limited. More attention to the IDD problem in Africa is urgently required. In southern Africa salt iodization could be an effective solution. In more severe endemias such as Zaire iodized oil has been used and will probably need to be continued. Many other countries fall between these extremes.

3.4 SOUTHEAST ASIAN REGION

This region has a major IDD problem in eight countries (See Table 6). Estimates are given in Table 10 and point to the large numbers of people affected, living in areas of defined environmental iodine deficiency where prevalence of goitre is more than 10 percent of the population. A full report is now available (Clugston and Bagchi, 1985).

TABLE 10

ESTIMATED POPULATIONS AT RISK AND PREVALENCE OF ENDEMIC GOITRE IN EIGHT COUNTRIES OF THE WHO SOUTHEAST ASIAN REGION (numbers in thousands)

Country

Total POP.

Population at risk (TGR > 10%)

Endemic goitre prevalence



Number

%

Number

%

Bangladesh

97 438

37 150

38.1

10 225

10.5

Bhutan

1 446

1 466

100.

946

65.4

Burma

39 920

14 545

36.5

5 694

14.3

India

746 010

149 588

20.0

7.3


Indonesia

161 003

29 773

18.5

9 759

6.1

Nepal

16 386

15 099

92.0

7 555

46.1

Sri Lanka

16 099

10 565

65.6

3 112

19.3

Thailand

52 709

20 439

38.8

7 740

14.7

TOTAL

1 131 011

278 605

24.6

99 349

8.8


Note:

TGR = Total Goitre Rate (prevalence)
Percentages shown are percentages of total population
Source: Clugston and Bagchi (1985, p. 14) and for total population data UN Demographic Yearbook 1981/1982

An important indication of the severity of IDD is given by determinations of blood T-4 and TSH on cord blood samples from neonates in Gonda, Uttar Pradesh, as compared with New Delhi (Table 11). These data indicate a 4 percent rate of neonatal hypothyroidism.

TABLE 11

UMBILICAL CORD BLOOD T-4 AND TSH BY DIRECT ASSAY

Mean Values (± SE)

Area

No. subjects

T-4 mcg/dl

TSH mcU/ml

Hypothyroids detected

Gonda

132

5.75 ± 0.2

15.50 ± 2.8

5

New Delhi

160

8.5 ± 0.2

8.7 ± 0.5

1

mcU - microunit Source: Kochupillai et al., 1984
Source: Kochupillai et la,. 1984
Follow-up is required in order to evaluate the persistence of such rates and to determine whether these infants are likely to develop permanent brain damage. A preventive programme is urgently needed (preferably with iodized oil).

The persistence of goitre in the face of a national iodized salt programme in India has been well documented by the Ministry of Health (Table 12). The findings show the need to monitor the iodization programme and urgently consider remedial measures, including the possible use of alternative technology. (See Section 6).

Conclusion

The largest populations living in iodine-deficient environments and therefore at risk of IDD are to be found in Asia. There is an enormous opportunity to improve quality of life and productivity by correcting iodine deficiency in these countries.

TABLE 12

IMPACT OF IODIZATION PROGRAMMES IN INDIA

District/ state

Baseline survey year

Prevalence percentage rate

Commencement of salt supply

Resurvey year

Prevalence percentage rate

HIMACHAL PRADESH

Sirmoor

1959

35.8

1963

1980

28.07

Kangra

1956

41.2

1962

1962

32.10

PUNJAB






Gurdaspur

1961

52.3

1964

1969

42.30

Hoshiarpur

1961

40.3

1964

1969

23.60

Chandigarh

1969

11.2

1968

1977

45.90

BIHAR






Champaran(East and West)

1960

40.3

1964

1979

64.51(East)






57.20(West)

WEST BENGAL






Darjeeling

1965

34.5

1967

1975-76

35.58

UTTAR PRADESH






Dehra Dun

1965

39.7

1966

1969

16.90

Bijnore

1960

23.2

1960

1969

23.60

Source: Nutrition Foundation of India, 1983

3.5 WESTERN PACIFIC REGION

A report from China indicates a massive problem with about 30 percent of the population at risk of IDD (Table 13). Effective programmes have been operating since 1978. In that time, it was claimed that IDD have been completely controlled in six of 27 provinces (mainly with iodized salt), but in another 11 provinces the programmes, although started, have not yet been adequately established and shown (through monitoring) to be effective. There are about 10 million people in Xinjiang and Tibet who need an iodized oil programme, but transportation in these provinces is very difficult (Ma, 1984). Limited data from Vietnam, Laos and Kampuchea indicate that severe IDD exist. (See Table 6).

TABLE 13

EXTENT AND EFFECT OF IODIZATION PROGRAMMES IN THE PEOPLE'S REPUBLIC OF CHINA

Population at risk of IDD

Methods of IDD Correction

Population covered by Programme

Evaluation Dates

Remarks

1983:
310,000,000 Some south China provinces not included

Chiefly iodized salt programmes, Certain areas use iodized oil injection

1984:
270,000,000 Some 60,000,000 people at risk not covered by iodization programmes

Among the 27 provinces with IDD endemia:
1. IDD controlled in 6 provinces by 1984.
2. Iodization programmes not well established in 11 provinces by 1984.

Although 310,000,000 are at risk of IDD under iodization programmes more than one third are not well quantified. Modern monitoring systems lacking to guarantee the quality of iodization programmes

1984:
330,000,000 Still some China provinces not included

Additional iodized oil injections for young married women in certain areas


Source: Ma Tai, 1984 Conclusion
China has made remarkable progress with salt iodization since 1978. This indicates the priority of prevention in the country's political philosophy. (See Sections 6 and 8).

3.6 GENERAL CONCLUSIONS

These data indicate a massive global problem. Where IDD have disappeared in Western countries, this has been brought about by an increased dietary intake of iodine either through specific supplementation with iodized salt or by dietary diversification as one of the outcomes of economic development. The problem can be expected to persist in the absence of either of these factors. Therefore the effects of iodine deficiency in the form of IDD on growth and development (Section 2) will continue to be evident. National and international action is indicated. Priority should be given to those areas and regions where the persistence of severe IDD can be anticipated as already pointed out in Section 1.


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