Asthma in developing countries managing an increasing burden

Transcription

1 Asthma in developing countries managing an increasing burden Heather J Zar School of Child and Adolescent Health Red Cross War Memorial Children s Hospital University of Cape Town South Africa Correspondence: Prof Heather Zar 5 th floor ICH building Red Cross War Memorial Children s Hospital Rondebosch, 7700 South Africa heather.zar@uct.ac.za Tel: Fax:

2 Asthma is common in children in many developing countries. The most reliable information on the global prevalence of childhood asthma has come from the International Study of Asthma and Allergies in Childhood (ISAAC) studies. These studies used cross sectional questionnaires to survey the prevalence of asthma symptoms in children of two age groups (6 to 7 years and 13 to 14 years) to investigate time trends in global prevalence. ISAAC Phase 1, the initial epidemiological survey was repeated five to 10 years later as ISAAC Phase 3. In most countries surveyed, the prevalence of asthma in children aged 6 to 7 years increased, whereas the prevalence in those 13 to 14 years stabilized or decreased in many developed countries. 1-3 In contrast, in most developing nations, the prevalence of asthma in adolescents also increased. 1,3 Whereas the prevalence in most English speaking countries has declined, substantial increases in asthma prevalence have occurred in Latin American countries such as Costa Rica, Panama, Mexico, Argentina and Chile, Eastern European countries such as the Ukraine and Romania, some African countries like Tunisia, Morocco, Algeria and South Africa and others including Barbados, Indonesia and China. 3,4 Thus, these results indicate that in many developing countries the prevalence of asthma in children is increasing, in contrast to that in developed populations where the prevalence has stabilised or is decreasing. 1-3 The large variations in the worldwide prevalence of symptoms of asthma reported even in genetically similar groups, suggest that environmental factors influence the expression and severity of asthma. The rising prevalence of asthma has been ascribed to a number of factors including a reduction in the prevalence of childhood infections, change in diet and lifestyle, economic development, and increased exposure to allergens or pollutants. 5-8 Large differences in urban-rural prevalence rates have been reported in African children of the same genetic background. 9 Yet, recent data suggests that the asthma prevalence in rural children is also increasing and that the urban-rural gradient has declined. For example, less than 30 years ago, asthma was reported to be relatively rare among Xhosa speaking South African children particularly those living in rural areas, with a 10 fold difference in the urban-rural prevalence of 3.2% and 0.1% respectively. 9 Two recent studies, done in the same geographical area, found that the prevalence has risen in both urban (to more than 15%) and rural areas (to more than 8.5%), with a marked reduction in the urban-rural gradient to approximately 2. 10,11 2

3 While a lifestyle of affluence has been associated with a higher asthma prevalence, poverty is associated with more severe asthma, higher morbidity and an increased risk of fatal asthma. 12 In addition, the importance of non-atopic asthma has increasingly been recognised in children in developing countries, accounting for a large proportion of children with asthma. 13 Children with non-atopic asthma generally have an earlier onset of asthma, more frequent history of pneumonia and increased exposure to household environmental tobacco smoke compared to those with atopic asthma. 13 Whatever the aetiology, increasing numbers of children in developing country settings can be expected to develop asthma given the population growth and changing pattern of urbanisation and lifestyle in these countries. Furthermore, in developing country settings, children account for a greater proportion of the population compared with developed countries. In 2005, children under 15 years of age comprised approximately 31% of the total population in developing countries, compared to 17% in developed nations. Thus, even a small rise in asthma prevalence may have important public health implications in these countries. Diagnosis of asthma in children in developing country settings poses particular challenges to health care professionals. Diagnosis is complicated by the high prevalence of tuberculosis (TB), HIV-associated lung disease and other poverty related lung conditions. Moreover, non atopic asthma may be more challenging to diagnose in young children; development of an asthma predictive index for children with wheezing relies on the associated features of atopy. Under-recognition and under-treatment of a large proportion of children with asthma is a consistent feature globally. Global surveys have confirmed unnecessary morbidity as limitation of activities, absenteeism from school, nocturnal wakening and hospitalisations due to inadequate recognition and treatment of asthma even in developed nations. 14 In developing countries where health care systems are already overwhelmed by the HIV pandemic and infectious diseases and where health care resources are limited, under diagnosis and under treatment are even more problematic. Diagnosis in infants or children under 5 years of age may be especially difficult given the high incidence of viral respiratory infections which frequently present with wheezing and the unavailability of objective measures of lung function in young children. Yet, accumulating evidence indicates that sustained control of all clinical features of 3

4 asthma can be achieved with adequate preventative therapy. 15 This is reflected in recent revisions of international asthma guidelines which now advocate a controldriven approach to asthma management. 16 Providing effective asthma management may be particularly challenging in developing country settings. Even when the diagnosis of asthma has been made, effective treatment is frequently unaffordable and inaccessible Inhaled therapy, the current standard of care for both prophylaxis of persistent asthma and relief of acute attacks, is frequently unavailable. A questionnaire administered in 24 countries in Africa and Asia reported that inhaled steroids were available to only 37% of respondents and prescribed in 5%; inhaled bronchodilators were available to 83% and prescribed by 29%. 18 In contrast, oral theophylline and bronchodilators were available in almost all cases and prescribed by 73% and 85% respectively. A survey of the availability and affordability of essential asthma medicines in 8 developing countries found that these were unaccessible in most. 19 In 80% of countries, the cost of 1 years supply of essential drugs for treatment of a person with moderate persistent asthma, exceeded the monthly salary of a nurse in that country. 19 Cost and availability of asthma drugs are therefore an important barrier to effective management in many developing countries. But use of inhaled corticosteroids is cost effective as shown in a paediatric study from Costa Rica. 20 Moreover, the emergence of generic formulations and creation of an asthma drug facility by the International Union against TB and Lung Diseases, has made asthma therapy more affordable. 21 An additional obstacle to effective inhaled therapy for children in developing countries is the lack of low cost spacer devices. 22 However, low cost homemade devices with demonstrated efficacy, in particular a modified 500ml plastic soda bottle have been developed and can be relatively easily made and used. 23,24 Poor access to care, particularly in impoverished rural communities is an important obstacle to effective asthma management. Lack of transport, long distances to the nearest health facility and poor telecommunication facilities may further complicate management. Developing appropriate education and action plans for acute and chronic asthma in such situations is challenging. Asthma education programmes that are language and culturally appropriate to specific developing country populations need to be established. The place of traditional medicines in asthma therapy is also 4

5 worthy of consideration as such remedies are widely used in some developing countries. New therapies for asthma including long acting β 2 agonists, combination therapy or leukotriene receptor antagonists have had less impact in developing countries where access and affordability to such treatment is poor compared to that in developed nations. A survey of the price of therapy in selected low- and middle-income countries, reported that the cost of one month of combination treatment for asthma ranged from 1.3 days wages in Bangladesh to 9.2 days wages in Malawi. 25 Nevertheless, effective asthma therapy in the form of inhaled corticosteroids for prophylaxis and inhaled bronchodilators with or without oral corticosteroids for acute episodes, should be widely available as these drugs from part of the World Health Organisation s essential drug list. The availability of inhaled therapy for relief and prophylaxis is regarded as the bare minimum for good asthma management in developed countries; such therapy has also been reported to be cost effective. 20 Children with asthma living in developing countries should receive no lesser treatment. Greater advocacy and education is needed to ensure access to such therapy for all children in the developing world who need it. References 1. Asher MI, Montefort S, Bjorksten B, et al and the ISAAC Phase Three Study Group. Worldwide trends in the prevalence of symptoms of asthma, allergic rhinoconjunctivitis and eczema in childhood: ISAAC Phases One and Three repeat multicountry cross-sectional surveys. Lancet 2006;368: Ait-Khaled N, Odhiambo J, Pearce N et al. Prevalence of symptoms of asthma, rhinitis and eczema in 13- to 14-year-old children in Africa: the International Study of Asthma and Allergies in Childhood Phase III. Allergy 2007: 62: Pearce N, Aı t-khaled N, Beasley R et al. Worldwide trends in the prevalence of asthma symptoms: phase III of the International Study of Asthma and Allergies in Childhood (ISAAC).Thorax 2007;62: Zar HJ, Ehrlich R, Weinberg EG. The changing prevalence of asthma, allergic rhinitis and atopic eczema in African adolescents from 1995 to Pediatr Allergy Immunol ;18(7): Stewart AW, Mitchell EA, Pearce N, et al. The relationship of per capita gross national product to the prevalence of symptoms of asthma and other atopic diseases in children (ISAAC). Int J Epidemiol 2001;30: Ellwood P, Asher MI, Bjorksten B, et al. Diet and asthma, allergic rhinoconjunctivitis and atopic eczema symptom prevalence: an ecological analysis of the International Study of Asthma and Allergies in Childhood (ISAAC) data. ISAAC Phase One Study Group. Eur Respir J 2001;17:

6 7. Burr M, Emberlin JC, Treu R, et al. Pollen counts in relation to the prevalence of allergic rhinoconjunctivitis, asthma and atopic eczema in the International Study of Asthma and Allergies in Childhood (ISAAC). Clin Exp Allergy 2003;33: Shirtcliffe P, Weatherall M, Beasley R. An inverse correlation between estimated tuberculosis notification rates and asthma symptoms. Respirology 2002;7: Van Niekerk CH, Weinberg EG, Shore SC, Heese HdeV, Van Schalkwyk DJ. Prevalence of asthma: a comparative study of urban and rural Xhosa children. Clin Allergy 1979; 9: Steinman HA, Donson H, Kawalski M, Toerien A, Potter PC. Bronchial hyper-responsiveness and atopy in urban, peri-urban and rural South African Children. Pediatr Allergy Immunol 2003; 14(5): Calvert J, Burney PGJ. Increase in prevalence of exercise induced bronchospasm in a rural and urban population of African school children. Current Allergy and Clinical Immunology 2003; 16(3): Poyser MA, Nelson H, Ehrlich RI, Bateman ED, Parnell S, Puterman A, Weinberg E. Socioeconomic deprivation and asthma prevalence and severity in young adolescents. Eur Respir J 2002; 19: Castro-Rodriguez JA, Ramirez AM, Toche P, Pavon D, Perez MA, Girardi G, Garcia-Marcos L. Clinical, functional, and epidemiological differences between atopic and nonatopic asthmatic children from a tertiary care hospital in a developing country. Ann Allergy Asthma Immunol. 2007;98(3): Rabe KF, Vermiere PA, Soriono JB, Maier WX. Clinical Management of Asthma in 1999: The Asthma Insights and Reality in Europe (AIRE) Study. Eur Respir J 2001; 16(5): Bateman ED, Boushey HA, Bousquet J, et al. Can guideline-defined asthma control be achieved? The Gaining Optimal Asthma Control Study. Am J Respir Crit Care Med 2004;170: Global Initiative for Asthma (GINA). Global strategy for asthma management and prevention. Workshop Report. 2006, Parry H. Treating asthma in developing countries: a problem of inaccessible unavailable essential medication. Thorax 1997;52: Watson JP, Lewis RA. Is asthma treatment affordable in developing countries? Thorax 1997;52: Aït-Khaled N, Auregan G, Bencharif N et al. Affordability of inhaled corticosteroids as a potential barrier to treatment of asthma in some developing countries. Int J Tuberc Lung Dis. 2000;4(3): Perera BJC. Efficacy and cost effectiveness of inhaled steroids in asthma in a developing country. Arch Dis Child 1995;72: Ait-Khaled N, Enarson DA, Bissell K, Billo NE. Access to inhaled corticosteroids is key to improving quality of care for asthma in developing countries. Allergy. 2007;62(3): Zar HJ, Weinberg EG. Spacer devices for the developing world. ACI International 2002;14(1): Zar HJ, Brown G, Donson H, Brathwaite N, Mann MD, Weinberg EG. Home-made spacers for bronchodilator therapy in children with acute asthma: a randomized trial. Lancet 1999;354: Zar HJ, Streun S, Levin M, Weinberg E, Swingler G. Randomised controlled trial of the efficacy of a metered dose inhaler with bottle spacer for 6

7 bronchodilator therapy in acute lower airway obstruction. Arch Dis Child. 2007;92: Mendis S, Fukino K, Cameron A, Laing R, Filipe A Jr, Khatib O, Leowski J, Ewen M. The availability and affordability of selected essential medicines for chronic diseases in six low- and middle-income countries. Bull World Health Organ. 2007;85(4):