Pediatric Pulmonology, Supplement 23:35-37 (2001)

Epidemiology of Asthma in Portugal, Cape Verde, and Macao

Mario Morais de Almeida, Angela Gaspar, and Jose Rosado Pinto

INTRODUCTION

It is generally accepted that a close relationship exists between asthma, atopy, and bronchial hyperresponsive- ness (BHR), and for some authorities, those entities may occur in a dependent way in school-aged children. Never- theless, the multifactorial genesis of asthma allows for the understanding that different gene combinations under the influence of several different environmental risk factors can express the same phenotype. Based largely on the body of evidence assembled thus far, and based on our clinical experience, we have shown that it is possible to have atopy with low asthma expression, and asthma with no significant atopy or bronchial hyperresponsiveness.

THE PORTUGUESE STUDY OF ALLERGIC DISEASES IN CHILDHOOD

BACKGROUND

Some important pediatric epidemiological projects, such as the ISAAC study, are conducted on a worldwide basis. The particular importance of the ISSAC study is the uniformity of data collection, as far as the different languages allow.’ Since 1993, our group has been enga- ged in a long-term study in Portuguese-speaking re- gions, applying the same methods in children with different genetic and environmental backgrounds. Our main objectives were: 1) to assess atopy and allergic diseases prevalence in random samples of school children, 2) to obtain baseline measurements for future comparisons.*

The regions included in our study are:

A) PORTUGAL-Madeira Archipelago, located in the Atlantic Ocean, nearby the Morocco coast, with a sub-tropical climate, like Cape Verde. It is one of the four Archipelagos that compose the Macarone- sian Islands. The ethnic majority is Portuguese

B) CAPE VERDE-Located in the Atlantic Ocean, in Guinea Gulf, near the west coast of Africa. It shares the same volcanic origin as Madeira, and has a tropical climate, but the rainfall is rare. Discovered

(99%).

0 2001 Wiley-Liss, Inc.

as a desert island, it was a Portuguese overseas province until 1975, when it became an independ- ent republic. The ethnic majority is Creoles; the remainder is mostly Black Africans with a small number of Caucasians. In Sal Island, the majority of the population is Black African; in S. Vicente Island, the majority is mainly Creoles, with influence from Portuguese and also Northern European people. MACAO-Located on the southern coast of China. It has a subtropical climate, with significant rainfall. After more than four centuries of Portuguese administration, it became a Chinese territory in December 1999. The principal ethnic majority is Chinese (more than 75%), predominantly Canto- nese. The remainders are mixed Chinese-Portuguese descendants and Portuguese.

C)

METHODS

In 1993, 235 African children from Sal Island, aged 6 to 16 years were studied; in 1994, a sample of 588 children aged 6 to 10 years was included from S. Vicente Island. The majority of these children were Creoles. In 1995, 1061 Caucasian children, aged 6 to 10 years, were studied in Madeira Island, and in 1997, 1385 Chinese children, aged 6 to 12, were studied in Macao. The methods used were an investigator-applied standard questionnaire and a battery of skin prick tests. In the children with wheezing in the last year, and in matched controls (age and sex), a methacholine challenge test was performed. Atopy was defined as at least one positive skin prick test; bronchial hyperresponsiveness (BHR) was considered positive if PD20 FEVl for methacholine was lower than 7.8 p moles. “Asthma ever” was defined as the cumulative lifetime diagnosis. Active asthma identified those children with symptoms during the previous year, and current asthma was considered if a

From the Immunoallergy Department, Dona Estefhia Hospital, Lisbon, Portugal.

Address correspondence and reprint requests to Dr. Mario Morais de Almeida, Immunoallergy Department, Dona Estefinia Hospital, Lisbon, Portugal.

36 de Almeida et al.

positive bronchial challenge test was found in children with active asthma.

RESULTS

The results from Cape Verde and Madeira revealed a significantly different prevalence of atopy. Preva- lence ranged from 6% in Sal Island to 11.9% in S. Vicente Islands to 54% in Madeira. House dust mites were the main source of sensitization. The prevalence of active asthma was 7% in S. Vicente and 14.6% in Madeira. Among asthmatics, the percentage of positive skin and bronchial challenge tests showed significant variations (from 12% to 74% and 25% to 70%, respectively).

As expected, the prevalence of current asthma showed a good correlation with atopy (the higher the prevalence of atopy, the higher current asthma prevalence due to the close association between atopy and BHR). But when we looked at children with active wheezing, and the degree of severity quantified as the number of exacerba- tions, we found more prevalence of non-atopic wheezing in Cape Verde. Indeed 10% and 7% of the wheezing children from Sal and S. Vicente Islands had more than 12 attacks in the previous year versus 3% only in Madeira.

When we looked at Macao, nearby Hong Kong, we found a significant prevalence of atopy, although lower than in Madeira (46% in Macau vs. 54% in Madeira, P<O.O5), with a large percentage of children with multiple sensitizations. Once again, house dust mites were the predominant allergens.

According to the atopic status of the population, the extremely low prevalence of active asthma (1.3%) and “asthma ever” (3.5%) was not expected. Most of the asthmatic children were atopic (86%), and most had a

positive BHR test (88%). The correlation with data published by Leung et al.3 was of interest. Giving comparable age groups, asthma prevalence was identified as intermediate in Macao, between Hong Kong and San Bu, China, but the rhinitis and eczema prevalence was quite similar to that identified in Hong Kong, and much higher than the rates in China. Therefore, the role of risk factors for specific targets, such as the upper and lower airways, namely the protective ones, must be identified. We showed that it is possible to have atopy with very low asthma expression.

In 1996 and 1997, three years after the first study in Cape Verde, we re-evaluated more than 95% of the child- ren with previous active asthma. More than one third of the cases were still symptomatic, and most of them were those with more severe wheezing. At the time of the re- evaluation, their ages ranged from 9 to 18 years. The per- centage of positive bronchial challenge responders was quite similar.

Finally, in January 1999 on Sal Island, we randomly studied 175 children, aged 6 to 10 years, and correlated the results with those obtained in the same age group (1 80 students studied six years earlier in 1993). The methods were the same: questionnaire and prick tests with the same standardized allergens.

The atopy prevalence had increased three fold (6% to 18%). All the allergens tested showed the same trend (Fig. 1). The prevalence of active asthma was unchanged (15% vs. 16%), but the percentage of atopic asthma increased from 2% to 5%. Perhaps, this trend is probably related to a more modem way of living.

Furthermore, this difference could be explained by the availability of medical care and resources, and the different criteria for prescribing antibiotics. The parti-

1 4 %

12%

10%

a Y.

6%

4 %

2%

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SAL ( 1 9 9 3 ) S A L ( 1 9 9 9 )

U D p t mDDf W G . Cockroach M o u l d s f f lCat l D o g B P o l l e n s

Fig. 1. Prevalence of sensitizations (global samples).

Epidemiology of Asthma 37

to these questions will allow for a better quality of life for allergic children.

cular diet of each population, for example, the low consumption of fresh food versus food that is industrially processed which dominates in the developed world, could also be a hypothesis to explain the results found.

CONCLUSION

The importance of these studies resides in allowing for some understanding and clarification of risk factors. In Macao and Madeira, we found an eleven-fold variation in active asthma (1.3% vs. 14.6%), but also a twenty-fold variation in maternal smoking (0.5% vs. 10%). The importance of passive tobacco smoke exposure in child- hood needs not be emphasized.

So, how can we prevent allergic diseases in childhood? How can we proceed from epidemiology to prevention? What have we learned? Which risk factor gives tolerance and protection, and how can we use it?

Perhaps, we should re-establish more traditional feeding practices and avoid allergens and pollutants, namely the indoor components. According to recent data, promoting other exposures such as living on farms or visiting cow and horse stables seems to have protective effects. Recent studies have shown that even among those rural resident children, low prevalence of atopy was found in farm residents or children with frequent stable visits.4 Bacterial endotoxin exposure early in life can also have an anti-inflammatory immune system modulator effect, acting on the Thl/Th2 balance, reducing atopy and allergic disease prevalence.

But several questions remain unanswered: When are these critical visits appropriate? During pregnancy or during the first years of life? For how long? And how long will the protective effect last? We hope that the answers

ACKNOWLEDGMENTS

Ministkrio da Saiide de Portugal, Ministkrio da Saiide da Republica de Cab0 Yerde, Secretarias dos Assuntos Sociais e da Educaciio da Regib Aut6noma da Madeira, Secretaria dos Assuntos Sociais de Macau.

COLLABORATORS

Hospital D. Estefhia, Lisboa: J. Rosado Pinto, M. Morais Almeida, N. Neuparth, h g e l a Gaspar, Graqa Pires, Cristina Santa Marta, Cristina Arcde, Anilia Matos.

Madeira: F. Drummond Borges, Rita Cimara, Ana Marques, Paula Omelas, J. Romeira. Cape Verde: CCu Teixeira, Dulce Vieira Lopes, Ana Helena Andrade, J. Figueiredo, J. Sousa Santos.

Macau: J. Humberto, Kin Mui Ieong, Isabel Andrade, N. Andrade, Chan Tzun, L. Weng Wai, N. Kin Hou.

REFERENCES

ISAAC Steering Committee. Worldwide variation in prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and atopic eczema: ISAAC. Lancet 1998;35 1: 1225-1232. Morais de Almeida M, Rosado Pinto J. Bronchial asthma in children: clinical and epidemiologic approach in different Portu- guese speaking countries. Pediatr Pulmonol 1999; 18(Suppl.):49- 53. Leung R, Ho P, Lam CWK, Lai CKW. Sensitization to inhaled allergens as a risk factor for asthma and allergic diseases in the Chinese population. J Allergy Clin Immunol 1997;99:594-599. Braun-Fahrhder C, Gassner M, Grize L, Neu U, Sennhauser FH, Varonier HS, Vuille JC, Wuthrich . Prevalence of hay fever and allergic sensitization in farmer’s children and their peers living in the same rural community. Clin Exp Allergy 1999;29:28-34.