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Page 1: A systematic review of recent asthma symptom surveys in Iranian children

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http://crd.sagepub.com/content/6/2/109The online version of this article can be found at:

 DOI: 10.1177/1479972309103884

2009 6: 109Chronic Respiratory DiseaseA Entezari, Y Mehrabi, M Varesvazirian, Z Pourpak and M Moin

A systematic review of recent asthma symptom surveys in Iranian children  

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REVIEW ARTICLE

A systematic review of recent asthma symptom surveysin Iranian children

A Entezari1, Y Mehrabi2, M Varesvazirian3, Z Pourpak4 and M Moin4

1Department of Community and Preventive Medicine, Shaheed Beheshti University MC, Tehran, Iran; 2Department of Epidemiology, School ofPublic Health, Shaheed Beheshti University of Medical Sciences and Health Services, Tehran, Iran; 3Department of Psychiatry, Iran University ofMedical Science and Health Services, Tehran, Iran; and 4Immunology, Asthma and Allergy Research Institute, Tehran University of Medical

Sciences and Health Services, Tehran, Iran

Asthma is the most prevalent chronic disease in children. To quantify the national prevalence ofasthma symptoms in Iranian children, we conducted a systematic review and meta-analysis.After internet and hand searching for population-based prevalence estimates published from1998 to 2003 from 142 articles, dissertations and reports of research projects, 19 of them wereselected. All the selected studies on children had been performed by the International Study ofAsthma and Allergies in Childhood (ISAAC) protocol. We analyzed the data using NCSS soft-ware. In the included 19 studies, 61,067 children in different age groups had been examined bythe ISAAC protocol. The lowest prevalence of asthma symptoms was 2.7% in Kerman and thehighest was 35.4% in Tehran (capital of Iran). Overall prevalence of asthma symptoms at anational level was estimated as 13.14% (95% CI: 9.97–16.30%). Based on this study, the preva-lence of asthma symptoms in Iran is higher than that estimated in the international reports. Thisinformation can be used to help prioritize asthma prevention and control within the range ofIranian public health concerns. Chronic Respiratory Disease 2009; 6: 109–114

Key words: burden of asthma; ISAAC; meta-analysis; prevalence

Introduction

Pediatric asthma is a major clinical concern world-wide and represents a huge burdenon family and soci-ety. It accounts for a large number of lost school daysand may deprive the child of both academic achieve-ment and social interaction. Childhood asthma alsoplaces strain on healthcare resources as a result ofdoctor and hospital visits and the cost of treatment.In Iran, asthma is an important cause of impairedquality of life, use of primary care, consumption ofprescribed drugs, hospital admission, and mortalityacross the whole range of age, sex, ethnicity, socio-economic status, and geographical location.1,2Asthma is not just a public health problem for high

income countries; it also occurs in developing nationsand especially in polluted and heavy traffic cities. Theprevalence of asthma is rising in many parts of theworld, but it is unclear whether this is due to an actualincrease in incidence or increase in allergic disorders.3

According to World Health Organization (WHO)estimates, 300 million people suffered from asthmaand 255,000 people died of asthma in 2005.4 The prev-alence rate of asthma increases as communities adoptwestern lifestyles and become urbanized.4 It has beenestimated that there may be an additional 100 millionpeople with asthma by 2025.3 Based on global burdenof asthma, prevalence of current asthma symptoms inIran was reported to be 5.5% in all age groups andapproximately 10% in children.4

International surveys have been valuable sourcesfor understanding and managing asthma. The Inter-national Study of Asthma and Allergies in Child-hood (ISAAC) and other surveys have providedmuch needed information on the global patterns ofasthma prevalence from childhood to adulthoodand have generated new hypotheses for furthertesting and validation.5

Chronic Respiratory Disease 2009; 6: 109–114http://crd.sagepub.com

© SAGE Publications 2009 Los Angeles, London, New Delhi and Singapore 10.1177/1479972309103884

Correspondence to: Mostafa Moin, Immunology, Asthma and AllergyResearch Institute, Tehran University of Medical Science andHealth Services, Tehran, Iran. Email: [email protected] [email protected]

Reprint requests: Abbass Entezari, 7th floor, EducationalDevelopment Center (EDC), Deputy of Medical Education, Ministryof Health and Medical Education, Falamak Ave, Simaye Iran Ave,Shahrak Gharb, Tehran, Iran.

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The prevalence of children’s asthma is a concernfor both health authorities and the general popula-tion in terms of personal, social, and economic costs.For estimating the burden of asthma in children, anational health system requires many parameters.Prevalence of asthma is one indicator for this pur-pose. Many prevalence studies on asthma symptomsin childhood in Iran have been conducted, but few ofthese studies addressed the national prevalence ofasthma symptoms alone. The present study attemptsto estimate the prevalence of asthma symptoms inchildren at the national level by reviewing recentasthma symptom surveys in Iran. The aim of thisstudy is to provide a clearer picture of the prevalenceof asthma symptoms in children in Iran.

Methods

A review of asthma symptom surveys in Iran, con-ducted or published between 1998 and 2003, wasundertaken by a general literature search. Keywordsincluded “Asthma,” “Prevalence,” “Epidemiology,”“ISAAC,” and “Survey.” We searched the Iranianscientific and medical internet databases such asIRANDOC, IRANMEDEX, SID, and MAGIRANfor all documents such as Persian articles, disserta-tions, conference proceedings, and other reportsabout asthma. Then, we searched on PUBMED and

Google for English articles and conference proceed-ings. The following initial selection criteria wereused: observational survey design, patient reportedoutcomes, perceptions or data related to asthma man-agement. Additional hand searching was performedon Persian dissertations and conference proceedingsabout asthma. Data from all studies were extractedin a systematic fashion into a large two-dimensionalmatrix. This approach simplified identification of sub-sets of surveys in which the methods, including design,populations, and outcomes, were sufficiently similarfor possible pooled analysis. The following maincriteria were used to structure the matrix: the periodof data collection, the nature of data extraction(interview/self-reported questionnaire), and question-naire type (standardized/ISAAC), location, design(cross-sectional/longitudinal), the sampling method,sample composition and size, and population demo-graphics. After the “extraction phase”, appropriatedata were selected. From a total of 142 surveys ini-tially screened, 21 surveys (including some subpopula-tions of special studies) were selected. Two surveyswere on adults and were excluded. Finally, 19 surveys,which were conducted on children less than 18 yearsusing ISAAC protocol, were included in the study.A list and overview of the design of surveys reviewedare provided in Table 1.6–24 All studies were con-ducted in urban regions. We analyzed data usingNCSS 2003 software (Number Cruncher StatisticalSystem, Kaysville, Utah, USA).

Table 1 Included studies on prevalence of asthma symptoms by first author or researcher, location, sample size, and percentagesof prevalence

Study number Researcher/author Place of studyStudy orpublication year Sample size

Prevalence of asthmasymptoms (%)

1 Janghorbani et al. [6] Kerman 1998 2217 2.702 Heidarnazhad et al. [7] Tabriz 2000 1147 3.953 Amra et al. [8] Shahre Kord 1998 700 5.004 Abbasi et al. [9] Guilan 2002 6060 5.605 Golshan et al. [10] Borujerd 2000 1331 5.706 Golshan et al. [11] Zarrinshahr 1999 1424 5.907 Golshan et al. [12] Isfahan 2000 4069 7.308 Golshan et al. [13] Isfahan 1999 3982 7.609 Gharagozlou et al. [14] Kashan 1998 3000 10.0010 Mortazavi Moghadam et al. [15] Birjand 2002 3540 10.1011 Hatami et al. [16] Bushehr 2002 2699 10.1012 Boskabady et al. [17] Mashad 1999 4781 15.8513 Masjedi et al. [18] Tehran 2001 6127 16.0014 Zohal et al. [19] Ghazvin 2003 5068 18.0015 Golshan et al. [20] Isfahan 1999 3986 19.6016 Boskabady et al. [21] Mashhad 2000 5534 21.7017 Tootoonchi et al. [22] Tehran 2001 611 21.9018 Bazazi et al. [23]b Gorgan 2003 2800 28.2019 Mirsaeid Ghazi et al. [24]b Tehran 2003 2000 35.40

aAll studies were carried out by ISAAC protocol.bOutliers (excluded from meta-analysis in second stage).

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Forest plot was used for illustration of meta-analysis results. The size of the square representsthe sample size of the corresponding study in themeta-analysis and the line represents the 95% confi-dence interval of an effect estimate. The pooledestimate is marked with a diamond. The confidenceintervals of pooled estimates are displayed as a hor-izontal line through the diamond.25

Because the Cochran test showed heterogeneity,we used a random effect model. Q is calculated bythe formula given below:

Q ¼ ∑iWiðbPi−bPÞ2,

where Wi ¼ 1

VarðbPiÞand bP ¼ ∑iWiPi

∑iWi.

Wi is the weight, bP is prevalence of asthma symptomin all population, and Pi is prevalence of asthmasymptom in the ith study. Analysis was conductedfor four groups of data. At the first stage, all datawere analyzed. In the second and third stages, outliersand data of Tehran surveys were excluded, respec-tively. Data of Tehran surveys were analyzed sepa-rately. Finally, we divided all the studies into threesubgroups on the basis of the time of the study: beforeyear 2000, 2000, and after 2000, and thenwe repeatedthe data analysis by this categorization.

Results

The 19 surveys reviewed included a total of 61,076subjects less than 18 years from 13 provinces of Iran.The prevalence of asthma symptoms by ISAACprotocol varied from 2.7% in Kerman to 35.4% inTehran. As shown in Table 1, prevalence of allasthma symptoms varied from 16 to 35.4% in allpopulation of Tehran.

Prevalence of asthma symptoms is calculated as13.14% (95% CI: 9.97–16.30%) of all studies(Table 1). Figure 1 gives the forest plot showingthe prevalence of asthma symptom for each studyand also pooled estimates for three situations.After deletion of outliers, analysis was repeated. Inthis situation, prevalence of asthma symptom wascalculated as 9.56% (95% CI: 6.93–12.19%). In thelast stage, data of Tehran was omitted and preva-lence of asthma symptoms in all other regions ofIran was estimated as 11.07% (95% CI: 7.94–14.19%), which is shown in Figure 1. Prevalence ofasthma symptom in Tehran only was calculated

24.41% (95% CI: 11.19–37.64%) using weightedmean of 8738 subjects in three surveys.

Prevalence of asthma symptom is calculated as9.66% (95% CI: 1.99–17.32%), 9.52% (95% CI:4.99–14.04%), and 18.11% (95% CI: 12.28–23.93%), respectively, for before year 2000, 2000,and after 2000. Figure 2 shows mean prevalenceof asthma symptoms for each year from 1998 to2003.

0% 10% 20% 30% 40%Prevalence

12

4567

9101112

1314

15

16

8

171819

CombinedIndividual

Outliers

a

b

c

a All data b without outliers

c without Tehran

3

Stud

y nu

mbe

r

Figure 1 Forest plot of prevalence and 95% confidenceintervals. (The size of the square represents the sample sizeand the line represents the 95% confidence interval of an effectestimate.)

5.89

9.52

18.72

8.58

27.16

12.23

5

10

15

20

25

30

Mea

n pr

eval

ence

%

Year1998 1999 2000 2001 2002 2003

Figure 2 Mean prevalence of asthma symptoms for each yearfrom 1998 to 2003 in different studies in Iran.

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Discussion

Before discussing the findings, it is important toaddress methodological aspects of our study. Thestrength of this analysis is the relatively large num-ber of studies nationally. All studies had followedsame protocol. The weaknesses of our study arethat only one study (Masjedi, et al.18) is a trueISAAC study, but the other studies have used theISAAC protocol and have not been part of theinternational ISAAC research program and havetherefore not been part of the international datacenter checks of the data and methodology. Onesurvey had been conducted in children aged5 years (Tootoonchi22). The ISAAC protocol didnot cover this age group. The present review of19 patient surveys indicates that prevalence ofasthma symptoms in Iranian children is between2.7 and 35.4%. There are many differences in theprevalence of asthma in different regions in Iran,and it is similar to other studies that showed theexistence of geographic differences, within andbetween countries.26

Although many environmental risk factors forasthma have been identified, such as animal, mite,other allergens, cigarette smoke, genetics, and airpollutants,27 the reasons for this variation in preva-lence are unclear and likely to be related to severalfactors such as differences in lifestyle, diversity ofclimates, and herbaceous coverage in differentparts of Iran. Iran’s climate ranges from arid orsemiarid to subtropical along the Caspian coastand the northern forests. On the northern edge ofthe country (the Caspian coastal plain), tempera-tures nearly fall below freezing, and it remainshumid for the rest of the year. The northern partof Iran is covered by dense rain forests calledShomal or the Jungles of Iran (Gorgan). Kermanis a sprawling city at the margin of Dasht-e Kavir,Iran’s largest desert. Tehran is the capital of Iranand the largest city in the Middle East and is themost populated city in Southwestern Asia with apopulation over 7 million, and most Iranian indus-tries are headquartered in Tehran.

A number of protective factors against asthmaonset have been identified including having beenbreastfed for more than six months and havingolder siblings. There are a number of groups atgreater risk of developing asthma. Infants born ata low weight are also believed to be at increasedrisk of developing asthma during childhood oradolescence.1

The present analysis shows that the prevalence ofasthma symptom in Iranian children is higher thanin the international reports about Iran.4

Based on international evidence, the first hypo-thesis to explain the increasing prevalence of asthmasymptom is the increasing proportion of populationoverweight or obese and this trend parallels theincreasing prevalence rate of asthma.28 The secondhypothesis has become known popularly as the“hygiene hypothesis.” Several studies have shownthat having older or a greater number of siblingsprotects a child from developing asthma.29,30 Inaddition to the overweight/physical activity hypo-thesis and the hygiene hypothesis, many investiga-tors have sought to identify specific environmentalexposures associated with the development ofasthma. With the exception of specific work-related exposures,31 there are no results for describ-ing this at a national level in Iran. This condition hascreated a need for more information regardingasthma in Iranian children.

The prevalence of asthma symptom varies world-wide, possibly because of different exposure to respi-ratory infection, indoor and outdoor pollution, anddiet. It is unclear why the variation in the prevalenceof asthma is so large. The most comprehensive sur-vey is the ISAAC (International Study of Asthmaand Allergies in Childhood) program, the largeststandardized international study of asthma preva-lence in children ever undertaken. It obtained dataon asthma prevalence in over 700,000 children from156 centers in 56 countries worldwide, including5873 children from Rasht and Tehran centers inIran in 1998.5 In the first ISAAC program, preva-lence of asthma symptom in Iranian children wasreported as 10.9% and average of this prevalencein Middle East region is 10.7%, which varied from7.5% in Morocco to 17% in Kuwait.5 This regionaldifference is due to special socioeconomic status,high urbanization, diversity of climates, and specificherbaceous coverage especially in the northern partof country and air pollution in industrialized andlarger cities such as Tehran.

After 6 years, in the second ISAAC program, theprevalence of asthma symptoms in Iranian childrenwas estimated as 13.2% (6065 subjects) in 2004.According to this report, the absolute yearly rateof increase in asthma symptoms in Iran is 0.38%.32Pearce, et al. showed that mean yearly rate ofincrease in asthma symptoms in the world is 0.06%and 0.13% in 13–14 years and 6–7 years old chil-dren, respectively, from 1998 to 2004.33 It seemedthat yearly rate of increase in asthma symptoms in

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Iran is higher than the world trend. If the trend isindeed increasing, we would expect a 15% preva-lence of asthma symptoms in Iranian children by2012. As shown in Figure 2, the present meta-analysis showed the prevalence of asthma symptomsin Iranian children is an increasing pattern from1998 to 2003, but slightly decreased at 2000 and2002. According to this analysis, the prevalence ofasthma symptoms in primary school age children ishigher than that in junior high school age childrenin Iran, and it is similar to other internationalreports.33

This meta-analysis showed the prevalence ofasthma symptoms in Iran is higher than in the firstreport of ISAAC, but it is very close to recentISAAC reports about Iran. According to this analy-sis, asthma symptoms impact nearly 1.5 millionchildren in Iran, and if the trend is continued, nearly3.2 million children will suffer from asthma symp-toms in 2012.

The prevalence of asthma symptoms varies in dif-ferent parts of Iran, but the reason for this variationin prevalence is unclear. As described previously,this national difference is probably due to indoorand outdoor pollution, industrialization, urbanizedlifestyle, overweight and obesity in Tehran; specificherbaceous coverage and other allergens such asmites and animals in Gorgan with a higher preva-lence; and low humidity and aridity in Kerman withlower prevalence of asthma symptoms.

This information can be used to help prioritizeasthma prevention and control within the range ofIranian public health concerns, as well as to provideinformation needed for asthma prevention and con-trol planning throughout the country. The publichealth community has not yet adequately focusedon gaining an understanding of the asthma epi-demic. Without this, prevention is not possible.Unfortunately we have large gaps in knowledgeabout the prevalence, severity, and morbidity ofasthma in the general population to accuratelyassess the burden of asthma and make internationalcomparisons.

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