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January - March 2003: 
Volume 16, Issue 1

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Frequency and outcome of childhood bronchial asthma in the town of Larissa
Abstract
SUMMARY. The purpose of this study was to estimate the frequency of bronchial asthma in childhood in the town of Larissa and to assess the possible effects of social status, environmental factors, the child’s medical and family history on the course of the disease. A brief asthma questionnaire was distributed and completed by 754 families with at least one child attending a public day nursery in Larissa. Of these, 120 were found to have a child with symptoms consistent with asthma in the past year. Children were 4 8 years old and the questionnaire was completed by their parents. The International Study of Asthma and Allergy in Childhood (ISAAC)-Phase I questionnaire with additional items referring to the socio-economic status of the family, indoor environment factors and parental smoking habits was used. A child with asthma was identified in seventy families. Two years later the course of the disease was evaluated in 66 of those families, using a modified ISAAC questionnaire. The frequency of bronchial asthma in the study population was 9,3%, with the frequency of asthma attacks declining with age. The majority of the children had mild asthma. Allergic rhinitis was found in 31,4% and allergic dermatitis (eczema) in 14,2%. Parental smoking was not related to asthmatic attacks. Allergic rhinitis and conjunctivitis were strongly related to asthmatic attacks on reevaluation two years later. These results suggest an important role of atopic disease in the course of asthma and confirm the reports of declining attack frequency with advancing age. Pneumon 2003, 16(1):49-58.
Full text

Introduction

Asthma is one of the most important childhood diseases in developed countries.1‑3 Its incidence varies from 5 to 20% worldwide, shows large geographical variation and has being steadily rising in the past 30 years.4,5 The environment in which a child is growing up affects the course of the disease. A variety of factors, such as early childhood infections, house dust, atmospheric pollution, smoking (either active or passive) as well as medical and family history have been shown to play a role.6,7 A history of atopic disease and a family history of asthma aggravate the course of childhood asthma. In the majority of cases, asthma symptoms significantly subside after puberty. The purpose of the present study was to estimate the frequency of bronchial asthma in childhood in the town of Larissa and to assess the possible effect of the child's medical and family history on the course of the disease.

Material and Methods

A brief asthma questionnaire was distributed in 863 families with at least one child attending a public day nursery in Larissa. The study was conducted in 1998 and included all seven public day nurseries operating in Larissa. Seven hundred fifty four families responded and 120 of these reported respiratory symptoms in at least one child in the past year. To minimize false negative cases, any suspicion of recurrent respiratory disease as indicated by the answers to the questionnaire was considered a potential asthma case. Children were 4‑8 years old and the questionnaire was completed by their parents. The Respiratory Function Study Unit of the Laboratory of Physiology constructed the questionnaire used in this initial study phase, aiming to the greatest possible sensitivity in data collection from day nurseries. In the event that no asthma-related symptoms were reported, drugs occasionally used by the children were taken into account. Use of drug treatment for wheezing and asthma lead to inclusion in the second study phase. Those 120 families were asked to complete both the ISAAC questionnaire and an attached questionnaire with items related to indoor environment and socioeconomic status, so as to obtain an accurate estimation of the frequency of childhood asthma and other allergic conditions in Larissa. To enhance the reliability of the survey, parents were asked if "asthma" was ever diagnosed in their offspring, and the child's health booklet was reviewed. The ISAAC (International Study of Asthma and Allergy in Asthma) questionnaire (see Appredix) was constructed in 1991 aiming to optimize our knowledge on the epidemiology of asthma and allergic conditions.3,8 The ISAAC has received international recognition and consists of three phases aiming to assess the frequency of allergic conditions (asthma, allergic rhinitis, eczema) in an international and concerted manner, to investigate time trends and to make comparisons between countries. In phase 1, the prevalence of asthma in many countries was estimated. Phase 2, which began in 1998 and is currently in progress, was designed so as to examine the possible relationship between the disorder and certain risk factors. This phase has included an extension of the primary questionnaire, allergic skin testing, bronchial hyperreactivity testing, serum IgE determinations and genetic analysis. In phase 3, the time course of asthma, allergic rhinitis and eczema will be investigated and attempts to identify associations of the course of those conditions with environmental factors will be made. A slightly modified phase I questionnaire was used in the present study. The original questionnaire has three sections. Section 1 consists of 8 asthma-related items, section 2 of 6 items relating to allergic rhinitis and section 3 of 7 items relating to the presence of eczema. In our modified questionnaire section 1 includes 20 items.

An additional 31-item questionnaire on the family's socioeconomic status was attached to the ISAAC questionnaire as an introductory section (see Appredix). It includes items on the parents' educational background and profession, the family's living environment, parental smoking habits and the children's sporting activities. That questionnaire was based on a similar one produced by the Pediatrics Department of the University of Ioannina, Greece, for respiratory function screening in elementary school pupils in the years 1996-97.

A follow-up evaluation of those families found to have an asthmatic child was performed two years later. A modified ISAAC questionnaire, more brief and focused on items relating to the course of asthma, was used. The number of asthma attacks and hospital admissions for asthma exacerbations, as well as any change in smoking habits received special attention. In essence, the follow-up questionnaire was ISAAC-Section I without questions 1, 8‑10, 15‑20 that related to the identification of the disease. Families were contacted by phone and asked to complete the questionnaire. Of the initial 70 families, four had moved house and could not be easily reached. Thus, 66 families comprised the study sample in the second phase.

a. Coding: Data on the number of family members (siblings, any elderly persons living in the same house), as well as on family history were obtained from the questionnaire items that related to family status. Socioeconomic status was assessed based on the educational level and the profession of the parents. Three levels of education were considered, with secondary school regarded as a single unit, since in the last two decades virtually every student in Greece has attended secondary school for 6 years. Higher education was defined as at least two years of education after secondary school graduation. Family density was calculated by dividing the number of individuals living in a house by the number of rooms (low <1, moderate 1-2, high >2). Data relating to smoking habits were comparatively evaluated, with emphasis placed on indoor smoking.

b. Data processing: Data were analyzed using Pearson's chi-square (x2) and the Yates correction for continuity where necessary. The relationship between parental factors and the frequency of asthma attacks two years after initial evaluation was investigated. Variables taken into account included the child's gender, parental history of asthma, socioeconomic status of the family, exposure to parental smoking, a child's history of allergic rhinitis or eczema, family density and number of older siblings. A p value equal to or less than 0.05 was considered statistically significant. Statistical analysis was performed using SPSS 7.5 for Windows.

Results

Seventy families with at least one child with asthma-consistent symptoms comprised the study sample. Demographic data of the sample are shown in Table 1. The frequency of asthma was 9.3% (70/754). Of children with asthma symptoms, 45.7% were male and 54.3% were female. The children's mean age was 5.9 years. 68.6% of fathers and 58.5% of mothers had received higher education (Table 1). The majority of the children had mild asthma (Table 2). 75.7% of the children had one attack in the last year and only 2.8% had three attacks in a year. Eczema was reported in 14.2% of cases and allergic rhinitis in 31,4% (Table 2). As regards heredity, 38.6% of cases had at least one first- or second-degree relative with bronchial asthma (Table 3). The frequency of recurrent asthma symptoms on reevaluation two years later was 9.1% (Table 4). The number of asthmatic attacks was not greater than once in a year, and none of the cases required hospital admission. The presence of asthmatic attacks two years later was strongly associated with a history of allergic rhinitis and conjunctivitis (hay fever) (Table 5).

 

 

Table 1. Demographic characteristics of study sample (Larissa, 1998)

                                              Ν     Μ    SD       %

Child’s age(mean value)       70    5.9 1.17

Father’s age                                   70    39   4.30

Mother’s age                                 70 33.9   4.61

Gender – male                              32                           45.7

   No. of siblings

                  0                                 17           24.3

                  1                                 41           58.6

                  2                                   9           12.9

                  3                                   3             4.3

   Educational level of father

                 (years)

                 <6                                  3             4.3

                6-14                               19           27.1

                >14                               48           68.6

   Educational level of mother

                 (years)

                 <6                                  1             1.4

                6-14                               28           40.1

                >14                               41           58.5

   Maternal smoking                       28              40

   Paternal smoking                        42              60

 

 

Table 2. Demographic characteristics of asthmatic children

Variables                                               Mean value                          Comments

Asthma attacks in the past year                      1                       53 (74.3%) had one attack

                                                                                               6 (8.6%) had two attacks

                                                                                               2 (2.8%) had three attacks       

Absent from school (days)                             4                       53 (75.7%) less than 10 days   

Medical consultations                                    2                       62 (88.6%) less than 5 visits    

Hospital admissions                                       0                       53 (75.7%) none

                                                                                               11 (15.7%) one            

Other allergic conditions                               Ν                                        %

Allergic rhinitis                                              22                                      31.4

Eczema                                                         10                                      14.2

Allergic rhinitis and/or eczema                      27*                                     38.5

*5 children had both allergic rhinitis and eczema

 

 

Table 3. Frequency of asthma in the members of families with asthmatic children.

Family member 

with asthma            No. of families Percentage (%)

Mother                              6                 8.6      

Father                               4                 5.7      

Sibling                               6                 8.6      

Grandmother                     6                 8.6      

Grandfather                       5                 7.1      

None                               43               61.4

Total                                70             100.0

 

 

Table 4. Course of asthma two years later.

90.9%    no symptoms

9.1%      mild symptoms

 

 

Table 5. Allergic rhinitis-conjunctivitis and asthmatic attacks two years later (p<0.05).

                                 Αsthma attacks

Αllergic rhinitis             2 years later            

and conjuctivits           Yes         No          Total

Yes                               5           17             22

No                                1           43             44

Total                             6           60             66

 

Discussion

The frequency of bronchial asthma, as determined by the present study, was 9.3%, which is close to the values reported in the literature in the recent years.3‑5 The prevalence of childhood asthma in Europe varies from 7 to 11%. According to the first study on childhood asthma conducted in the whole of Greece in 1988, the prevalence of asthma in children aged 7‑8 years is approxima tely 7.3%.9 Recent studies conducted in the region of Thessaly report higher values, reaching a frequency of 8%.10 In Turkey the frequency of asthma was 9.8%, with the frequency of wheezing rising up to 15.1%.11 In the UK the prevalence of wheezing was 33% and that of asthma 20%.12 Approximately 70% of the parents were aware that their child suffered from asthma, whereas the rest used other terms for their child's condition (e.g. asthmatic bronchitis, spastic bronchitis or allergic bronchitis) without knowing that those terms are synonymous with asthma.

The frequency of wheezing and asthma is steadily rising in the last 30 years. It has been shown that the rise in the frequency of asthma is much greater than that of wheezing.13,14 This enhances the assumption that a large part of the increase in the frequency of asthma may be attributed to the ever increasing recognition of this condition as "asthma" and the obsolescence of terms widely used in the past such as "asthmatic/asthmatoid bronchitis" or "allergic bronchitis". There are significant variations in the prevalence of asthma both between different geographical areas and between studies.3 Those variations are in part due to differences in methods and diagnostic criteria employed in different studies. It seems, however, that there is also a genuine increase in the incidence of the disease. In Hong Kong the prevalence of asthma increased by 71% and that of wheezing by 24% within a few years.15 Similar findings are reported in many studies. In Aberdeen, Scotland, the prevalence of wheezing in childhood has increased from 10% in 1964 to 20% in 1989, whereas the prevalence of asthma rose from 4 to 10% in the same period of time. Eczema cases also increased from 6 to 12%, and the same is true for hay fever which has increased from 3 to 12%, indicating a generalized trend of increase in atopic disease cases.16 In relation to heredity, a positive family history of bronchial asthma is reported in 30‑60% of the cases.17 A parental (especially maternal) history of asthma or atopy is the strongest predictor for childhood asthma among other family history parameters.6 Studies on twins have shown that serum IgE levels in children and adults are genetically determined; furthermore, other studies have shown that there is a genetic basis for bronchial hyperreactivity, even in the absence of clinical manifestations of the disease.18,19

There is only a small number of studies addressing the incidence rates and the course of childhood asthma. A national survey conducted in Great Britain reported annual incidence rates 2.6%, 1.1%, 0.7% and 0.8% at ages 7, 11, 16 and 23 respectively.20 The general impression is that the incidence of asthma is greater in early childhood and declines as the child grows up and enters adolescence. The majority of infants and pre-school children experience transient episodes of wheezing; nevertheless, those episodes are not associated with increased risk of developing asthma or allergy later in life. A remarkable decline in the number of asthma attacks is generally observed when the child reaches puberty. However, unfavorable environmental factors, frequent viral infections and a predisposition to atopy contribute to the persistence of the attacks. The frequency of asthma in the present study is higher than that reported in a relatively recent study conducted in Greece, and by 15% higher compared to another study conducted in Thessaly five years ago.10 This difference was expected as it reflects the rise in the prevalence of asthma observed worldwide in the recent years.

The frequency of asthma attacks two years after the initial evaluation was 9.1%. The attacks were less severe, since none of the patients was admitted to hospital for treatment. The decline in the frequency of attacks reflects the general benign course of the disease with advancing age. Similar changes in the frequency of asthma in the longterm are reported in a study conducted in Great Britain; children were followed up from age 7 to age 30. At age 7, 18% of the children still had symptoms of asthma.21 According to the results of the ISAAC study, which included 2,561 children aged 13-14 years, the prevalence of asthma in Greece was estimated at around 5%, one of the lowest values globally.3

On reevaluation, two years later, asthma attacks were strongly related only to a history of allergic rhinitis. In contrast to other reports,10,20,22 a history of eczema was not found to be associated with recurrent attacks. Both allergic rhinoconjunctivitis and a history of eczema are known to be closely related to the incidence of asthma and the persistence of asthma symptoms in the course of the disease.23,24 Allergic rhinitis with concomitant conjunctivitis (hay fever) as a manifestation of atopy, is associated with high risk for persistence of asthma symptoms after the age of 20.25 In general, children with atopic conditions (hay fever, eczema) present a higher incidence of bronchial hyperreactivity, especially those sensitized to more than one groups of allergens.26,27 Furthermore, the degree of bronchial hyperreactivity is directly related to the degree of atopy. However, the remission of allergic rhinitis symptoms with the local use of steroids leads to an improvement in asthma symptoms.28 It is currently recognized that any factor that irritates the upper airways may cause an exacerbation of asthma. Even acute or chronic sinusitis may induce bronchial hyperreactivity.29 Other factors that have been shown to play an important role in the onset and course of asthma, were found to be less significant in the present study. Parental smoking habits and the number of cigarettes smoked indoors were not related to the severity of asthma, and this applies also to socioeconomic status. However, in agreement with other studies, maternal smoking, especially during pregnancy, and breast-feeding, is a significant risk factor for the development of asthma.30,32 The number of cigarettes smoked is also significant, with 10 cigarettes a day being a critical limit. However, smoking may not affect the course of asthma in late childhood.

There are some points and sources of potential bias that have to be recognized in the present study. Patients were followed up for only two years. Had the follow-up period been longer, it might have been possible to identify additional associations. The study sample, although randomly selected from the public day nurseries in the town of Larissa, may not be representative; moreover, families with a higher socioeconomic status may have preferred private nurseries. Another crucial point is that atopy cannot be properly assessed un young children without specific sensitization testing, given the high frequency of infections at that age. Parents may have given inaccurate answers to the questions on family history. Asthma is often confused with conditions such as chronic obstructive pulmonary disease or heart failure. In addition, many parents were not aware that terms like allergic or spastic bronchitis were synonymous with asthma. There is also a possibility that questions on childhood asthma were not candidly answered because of prejudice on the severity of the disease.

The present study had a preliminary character. Although it is difficult to arrive to safe conclusions, our findings pinpoint the role of a history of atopy in the outcome of asthma. The steady increase in the prevalence of asthma over the recent years is further confirmed. This study has also demonstrated a decline in the frequency of asthma attacks on reaching puberty.

 

 

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