Childhood asthma in a rural county

Clinically diagnosed childhood asthma and follow-up of symptoms in a Swedish case control study

Background

Childhood asthma has risen dramatically not only in the western societies and now forms a major and still increasing public health problem. The aims of this study were to follow up at the age of ten the patterns of asthma symptoms and associations among children with a clinically diagnosed asthma in a sizeable urban-rural community and to in compare them with demographic controls using a standardised questionnaire.

Methods

In a defined region in Sweden with a population of about 150 000 inhabitants, all children (n = 2 104) born in 1990 were recorded. At the age of seven all primary care and hospital records of the 1 752 children still living in the community were examined, and a group of children (n = 191) was defined with a well-documented and medically confirmed asthma diagnosis. At the age of ten, 86 % of these cases (n = 158) and controls (n = 171) completed an ISAAC questionnaire concerning asthma history, symptoms and related conditions.

Results

Different types of asthma symptoms were highly and significantly over-represented in the cases. Reported asthma heredity was significantly higher among the cases. No significant difference in reported allergic rhinitis or eczema as a child was found between cases and controls. No significant difference concerning social factors or environmental exposure was found between case and controls. Among the control group 4.7 % of the parents reported that their child actually had asthma. These are likely to be new asthma cases between the age of seven and ten and give an estimated asthma prevalence rate at the age of ten of 15.1 % in the studied cohort.

Conclusion

A combination of medical verified asthma diagnosis through medical records and the use of self-reported symptom through the ISAAC questionnaire seem to be valid and reliable measures to follow-up childhood asthma in the local community. The asthma prevalence at the age of ten in the studied birth cohort is considerably higher than previous reports for Sweden. Both the high prevalence figure and allowing the three-year lag phase for further settling of events in the community point at the complementary roles of both hospital and primary care in the comprehensive coverage and control of childhood asthma in the community.

Bronchial hyper-responsiveness and atopy in urban, peri-urban and rural South African children

Twenty years ago, the prevalence of atopic sensitization and bronchial hyper-responsiveness (BHR) in Xhosa children in a rural location in South Africa was very low. The aim of this study was to document the current prevalence of these two indices by comparing traditional rural Xhosa children, recently urbanized Xhosa children and established city white children, and to consider factors that may account for the observed increase in all of these groups. One thousand four hundred and fifty-seven school children aged 10-14 years from the rural Transkei, from a recently urbanized peri-urban area and from urban Cape Town areas were studied using a questionnaire. Four hundred and eighteen children had histamine challenges, and 492 tests for atopy were also conducted. As determined by bronchial challenge with histamine, 17% of rural and 34.4% of recently urbanized Xhosa children had increased BHR, a marked increase from the 0.03% and 3.17% prevalence of increased BHR previously found using the exercise challenge. The prevalence of increased BHR in white urban children was 33%. Sensitization to one or more aero-allergens, as indicated by CAP RAST tests, was present in 36.6% of the rural Xhosa children with normal BHR and in 62.5% of those with increased BHR, a striking increase from that of previous studies. Atopic sensitization to one or more aero-allergens, as indicated by a skin prick test (SPT), was found in 42.3% of the recently urbanized Xhosa children and 45% of urbanized white children. We have also documented sensitization to house dust mites in the rural Xhosa children for the first time. Passive cigarette smoking was not identified as a risk factor for increased BHR or atopy. Wood smoke in the indoor environment did not play a role in the rural Xhosa children's BHR. Ascaris infection does not appear to play any modifying role in the development of increased BHR in the rural or urban children. We have found that increases in BHR in the rural and recently urbanized Xhosa children develop independently of increases in atopy. Our results challenge the 'hygiene' hypothesis as a complete explanation for the recent dramatic worldwide increases in allergic diseases.

Prevalence of symptoms of asthma and allergies in schoolchildren in Gondar town and its vicinity, northwest Ethiopia

A low level of allergic disorders has been generally reported in children from developing countries. A survey was conducted to determine the prevalence of symptoms of asthma and allergies among schoolchildren in Gondar, northwest Ethiopia. A standardized self-administered questionnaire developed by the International Study of Asthma and Allergies in Children (ISAAC) was used. In total, 3,365 children aged 13-14 years were surveyed at school, with a response rate of 98.4%. The female to male ratio was 1.5:1. The 12-month-period prevalences of wheeze (16.2%), rhino-conjunctivitis (14.5%), and eczema (10.9%) were comparable to findings from Addis Ababa, but significantly higher than reported from Jimma. A striking seasonal pattern of rhinitis symptoms is observed during the months of September-December with a peak in November, corresponding with the main pollen season of the area. Overall, about 36% of the children reported symptoms of atopic disorders. However, the prevalence of diagnosed atopic diseases (8.6%) is less than a quarter of the symptom prevalence rate. This may reflect a generally poor awareness and low health service utilization, or underdiagnosis by health facilities. In conclusion, it appears that the prevalence of atopic diseases in Gondar area is high, and there is also wide variation within the country. This calls for further epidemiological studies with more objective assessments of atopy, such as allergen and bronchial hyperresponsiveness tests and ecological analysis.

Asthma in children: prevalence, treatment, and sensitization

This study compares the prevalence of asthma and sensitization in children from two Swedish regions with different climates: Göteborg on the southwest coast and Kiruna in the northern inland, north of the Arctic Circle. The 412 children of a population-based sample, 203 in Göteborg and 209 in Kiruna, were investigated at age 7-8 and 12-13 years. Questionnaire reports and interviews were obtained from all children at 7-8 years of age, and 192 children were skin-prick tested for common aeroallergens in Göteborg and 205 in Kiruna. At the follow-up, 5 years later, almost all the children were re-investigated. The prevalence of asthma, wheeze, and sensitization had increased with increasing age during the follow-up period. The questionnaire reports revealed that the prevalence of asthma was 8.5% at 12-13 years of age. All children who in the questionnaire reported current asthma, were using asthma medication. The interviews indicated that the prevalence of a clinically significant asthma might be even higher, reaching approximately 12%. Asthma and wheeze were as common in Göteborg as in Kiruna despite large differences in prevalence of sensitization. Sensitization, and especially sensitization to animals, was far more common in Kiruna than in Göteborg. This study shows that asthma and wheeze are increasingly prevalent even in school age children and that sensitization does not necessarily reflect the prevalence of asthma in a population.

Prevalence of bronchial asthma in schoolchildren in Delhi

There is a paucity of information on the prevalence of asthma in children in India. Some evidence suggests that asthma is less common in developing than in the developed countries. The present study was carried out to estimate its current magnitude in children in Delhi. The questionnaire-based study was carried out in two randomly selected schools in Delhi. All the children were eligible. The age range was 4-17 years. The questionnaires were distributed to all the children present (n = 2867) to be answered by either parent. The key questions were related to complaints of recurrent wheezing in the past, in the last 1 year, and also wheezing exclusively induced by exercise or colds. In all, 2609 questionnaires were completed and returned (response rate 91%). There was a slight excess of males (54%). The prevalence of current asthma was 11.6% and past asthma was reported by 4.1% of children, giving a cumulative prevalence of 15.7%. Exclusive exercise-induced asthma was 2.8% and that associated with colds, 2.3%. The current prevalence of all wheezing was thus 16.7% and cumulative prevalence was 20.8%. While there was no sex-related difference in prevalence, wheezers were the highest in the 9-13 year age group. A significant association was found between the prevalence of wheezing and a family history of asthma (odds ratio 3.65) and presence of smokers in the family (odds ratio 1.62). When both the above factors combined, the odds ratio for risk of asthma was 4.58. There was no significant association with any economic class. Only 11% of asthmatics had been labeled so by their physicians. The prevalence of bronchial asthma and wheezing in children in Delhi is quite high and comparable to that reported from several developed countries. A positive family history of asthma and presence of smokers in the family emerged as significant risk factors.

Genes, environments, and sex: factors of importance in atopic diseases in 7-9-year-old Swedish twins

Various atopic manifestations among adults have been shown to be influenced mainly by genetic factors. With the increase in prevalence of atopic diseases in recent years, especially among children, a great deal of attention has been given to environmental causes. In a study of 1480 Swedish twin pairs, 7-9 years old, we examined the importance of genetic and environmental factors in asthma, hay fever, eczema, and urticaria. Structural equation model fitting showed 33-76% of the variation in liability to the diseases to be due to genetic effects. Shared environmental effects were also important for hay fever and urticaria in both sexes and for eczema among girls. The clustering of atopic disease in families was almost entirely due to a common set of genes, but each disease manifestation also seemed to have specific genes of importance. Investigation of unlike-sex twins showed that boys had a higher cumulative incidence of asthma and hay fever than girls, whereas girls had a higher incidence of eczema. Thus, it may be concluded that although genetic factors are of major importance in atopic manifestation in children, both environmental and sex-related factors play a role.

Family dysfunction in asthma: a prospective study of illness development

The role of psychosocial factors in the development of wheezing was studied prospectively in 100 infants with a strong family history of allergy. The entire family participated in a standardized family test when the children were 3 and 18 months of age. The ability to adjust to demands of the situation ("adaptability") and the balance between emotional closeness and distance ("cohesion") were assessed from videotapes by independent raters. Families rated as functional in both aspects were classified as "functional" and otherwise as "dysfunctional." Based on records of symptoms kept by the parents and on results of physical examinations at 6 and 18 months of age, the children were classified as healthy or as having recurrent wheezing, recurrent infections, or eczema. An unbalanced family interplay was common (37%) at 3 months but did not predict development of illness. If the child remained healthy and the family did not experience any further stress, family interaction was functional 15 months later. If, however, the child acquired anxiety-provoking symptoms, such as wheezing, a high proportion of families continued or began to have dysfunctional interaction patterns. When the healthy children were 18 months of age, only 12% of their families were dysfunctional, compared with 26%, 46%, and 52%, respectively, of the families of children with eczema, recurrent infections, and obstructive symptoms (p < 0.01). We conclude that dysfunctional family interaction seems to be a result rather than the cause of wheezing in infancy.

Familial occurrence of atopic disease: genetic versus environmental factors

Cumulative life prevalence of atopic disease (any of reported symptoms of asthma/wheezy bronchitis, allergic rhinitis, eczema and urticaria) was studied by means of a questionnaire in 19814 (7-, 10- and 14-year-old) Swedish school children and their parents. Maternal history was found to be twice as common as paternal history. The children of affected mothers contracted atopic disease in the same proportion as the children of affected fathers yielding twice as many affected children with affected mothers than with affected fathers. The strongest parental influence on childhood disease was seen for multiple symptoms and for congruent symptoms with both parents. The number of children with both parents affected was 1.6 times larger than expected. A possible dose-response effect in polygenic inheritance is discussed as well as assumed impact of environmental factors with a tendency to familial clustering.

Prevalence of atopic disorders among adolescents in Turku, Finland

A study of the prevalence of atopic disorders among 15-16-year-old teenagers was carried out in a coastal urban town in south-western Finland. Altogether, 1712 children were found in that age group, all previously examined by a pediatrician. Each child who had present or previous allergic diseases was invited for a detailed study, a total of 434 (25%) pupils. Of these patients 416 (95.8%) participated in clinical examination and skin testing. The prevalence of atopic diseases was 21% in the studied group; atopic eczema was found in 9.7%, allergic rhinitis in 14% and asthma in 2.5%. Of subjects who had rhinitis, 38% also had atopic eczema, while rhinitis--as the only symptom--was found in 8.8%. Figures obtained from this survey suggest that the prevalence rates of atopic diseases are about the same as found 10 years ago in Finland and they correspond also with other recent reports.

Hay fever, eczema and urticaria in southwest Norway. Lifetime prevalences and association with sex, age, smoking habits, occupational airborne exposures and respiratory symptoms

Information on hay fever, eczema, urticaria, respiratory symptoms, smoking habits and occupational dust or gas exposure was obtained by a self-administered questionnaire from a random sample of 4992 subjects of the general population aged 15-70 years of the Hordaland county, Norway. The response rate was 90% of the sample. The lifetime prevalences of hay fever, eczema and urticaria were 10%, 25% and 9% of the respondents, respectively. Eczema and urticaria were more often reported by women than by men. The lifetime prevalence of hay fever decreased substantially by age in both sexes. A history of hay fever was inversely related to cigarette smoking. The lifetime prevalences of eczema and urticaria were associated with occupational dust or gas exposure after adjusting for sex, age, smoking habits and area of residence. Adjusted odds ratios of respiratory symptoms in subjects with hay fever were almost 2.0 compared with those without.

Natural history of allergic diseases in children

Questionnaire data from 1335 14-year-old children with a history of past or present asthma, allergic rhinitis or eczema were analysed regarding age at onset and cessation of symptoms. Incidence of asthma and eczema was highest during the first years of life. Early incidence of asthma was higher in boys than in girls but the sex ratio equalized gradually during childhood. Early incidence of eczema was equal between the sexes but the proportion of girls increased gradually with later age at onset. In 24% of the children more than one symptom was found. Cessation of symptoms was common in asthma (55%), in particular in those with early onset (74%), but less common in eczema (34%). Cessation of symptoms was less common in both diseases when associated with other allergic symptoms. Incidence of allergic rhinitis was fairly constant during childhood and cessation of symptoms was uncommon. A high risk of allergic airways disease was found after early eczema.

Birth season variation in asthma and allergic rhinitis

The prevalence of asthma and allergic rhinitis was analysed in relation to birth month in two cohorts of 18-year-old males born in 1953 (n = 55,393) and 1963 (n = 57,150), in schoolchildren (n = 19,814) and in children with defined specific allergies (n = 1080). Among the 18-year-olds, a marked variation with respect to birth season was only found in those born in 1963, with the highest prevalence of asthma in those born August-January and of allergic rhinitis in those born November-May. In the schoolchildren with allergic rhinitis the birth season pattern was found to be similar to that in the conscripts born in 1963. The influence of month of birth on the onset of allergic rhinitis was maximum about 6 years of age and was not seen before 2, and after 10 years of age. Obvious similarities in birth season patterns were found between the unselected populations and the children with defined pollen and animal dander allergies. The differences in birth season pattern between the two cohorts of 18-year-olds were interpreted as an effect of unidentified adjuvant factors that might have developed over a 10-year period.