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Epidemiology of asthma in primary school children: the Obstructive Lung Disease in Northern Sweden (OLIN) studies thesis VIII
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Childhood asthma has increased worldwide, although recent studies report a prevalence plateau in some western countries.

Aims: To investigate the prevalence of asthma and the associated risk factor patterns from ages 7-8 to 11-12 with special emphasis on the hereditary component, and further to study prevalence trends at age 7-8 from 1996 to 2006 and the possible determinants of these trends.

Methods: The studies involved two cohorts from Kiruna, Luleå and Piteå: one previously identified cohort of 3430 children age 7-8 followed by yearly questionnaires until age 11-12 with 97% yearly participation. Skin-prick tests for allergic sensitisation were performed at ages 7-8 and 11-12 in subsets of 2148 and 2155 children respectively (88% of invited). In 2006 a new cohort of 7-8-year-olds was identified and examined identically. 2585 (96% of invited) and 1700 (90% of invited) participated in the questionnaire and skin-prick tests, respectively. The questionnaire included questions about symptoms of asthma, allergic rhinitis and eczema, and possible risk factors.

Results: In the 1996 cohort, from age 7-8 to 11-12 the prevalence of physician-diagnosed asthma increased (5.7%-7.7%, P<0.01) while current wheeze decreased (11.7%-9.4%, P<0.01), and 34.7% reported ever wheee at ≥one occasion. Remission was 10% of which half relapsed during the study. Remission was significantly lower among sensitised children. The strongest risk factors for current asthma at ages 7-8 and 11-12 were allergic sensitisation (OR 5) and family history of asthma (OR 3). Several other significant risk factors, e.g. respiratory infections, damp house and low birth weight, had lost importance at age 11-12. At age 7-8, parental asthma was a stronger risk factor (OR 3-4) than parental rhinitis or eczema (OR 1.5-2). Sibling asthma had no independent effect. Biparental asthma had a multiplicative effect (OR 10). Maternal and paternal asthma was equally important, regardless of the child’s sex and sensitisation status.

From 1996 to 2006 the prevalence of current wheeze and asthma at age 7-8 did not increase (P=0.13, P=0.18), while lifetime prevalence of ever wheeze and physician-diagnosed asthma increased (P<0.01, P=0.01). Symptoms of rhinitis and eczema were unchanged, despite 45% increase (P<0.01) in allergic sensitisation. For current asthma the adjusted population attributable fractions of sensitisation and parental asthma increased (35%-41%, 27%-45%). This was however balanced by decreased exposure to infections, maternal smoking and home dampness, resulting in stable asthma prevalence. Stratification by sex revealed that current wheeze increased in boys (P<0.01) but tended to decrease in girls (P=0.37), seemingly due to symptom persistence in males. Several asthma indices followed this pattern. The boy-to-girl ratio in exposure to all studied risk factors increased, which may explain the sex-specific prevalence trends in wheeze.

Conclusions: The prevalence of current asthma and wheeze did not increase statistically significantly. However, the risk factor pattern has changed considerably since 1996, which will presumably affect the clinical features of childhood wheeze in this region. Sex-specific trends in wheeze can be explained by changes in exposure, and trends in risk factors should be explored parallel to prevalence trends.

Place, publisher, year, edition, pages
Umeå: Folkhälsa och klinisk medicin , 2008. , 79 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1162
Keyword [en]
Asthma, wheeze, child, allergic sensitisation, prevalence, remission, risk factor, trend
National Category
Respiratory Medicine and Allergy
Identifiers
URN: urn:nbn:se:umu:diva-1587ISBN: 978-91-7264-531-8 (print)OAI: oai:DiVA.org:umu-1587DiVA: diva2:141463
Public defence
2008-04-04, Sal D, 9 trappor, Tandläkarhögskolan, 901 85, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2008-03-17 Created: 2008-03-17 Last updated: 2016-03-11Bibliographically approved
List of papers
1. Asthma during the primary school ages--prevalence, remission and the impact of allergic sensitization.
Open this publication in new window or tab >>Asthma during the primary school ages--prevalence, remission and the impact of allergic sensitization.
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2006 (English)In: Allergy, ISSN 0105-4538, Vol. 61, no 5, 549-55 p.Article in journal (Refereed) Published
Keyword
Age Distribution, Asthma/*epidemiology, Child, Cohort Studies, Comorbidity, Female, Humans, Hypersensitivity/*epidemiology, Longitudinal Studies, Male, Odds Ratio, Prevalence, Prospective Studies, Questionnaires, Recurrence, Remission; Spontaneous, Respiratory Sounds/immunology, Risk Factors, Skin Tests, Sweden/epidemiology
Identifiers
urn:nbn:se:umu:diva-15050 (URN)10.1111/j.1398-9995.2006.01027.x (DOI)16629783 (PubMedID)
Available from: 2008-01-09 Created: 2008-01-09 Last updated: 2016-03-11Bibliographically approved
2. Family history of asthma and atopy: in-depth analyses of the impact on asthma and wheeze in 7- to 8-year-old children.
Open this publication in new window or tab >>Family history of asthma and atopy: in-depth analyses of the impact on asthma and wheeze in 7- to 8-year-old children.
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2007 (English)In: Pediatrics, ISSN 1098-4275, Vol. 120, no 4, 741-8 p.Article in journal (Refereed) Published
Abstract [en]

OBJECTIVES: Development of asthma in children is influenced by interactions between genetic and environmental factors. It is unclear whether paternal or maternal histories of disease confer different risks. Previous population-based studies have not stratified analyses by child gender and sensitization status. Our aim was to study in detail the hereditary component of childhood asthma. METHODS: A population-based cohort of 3430 (97% of invited) 7- to 8-year-old school children participated in an expanded International Study of Asthma and Allergy in Childhood survey, and two thirds were skin-prick tested. Heredity was defined as a family history of (1) asthma and (2) atopy (allergic rhinitis or eczema). Multivariate analyses corrected for known risk factors for asthma. RESULTS: At ages 7 to 8, prevalence of asthma was 5.3% among the children and 9.0% among the parents. In children without parental asthma or parental atopy, the prevalence of asthma was 2.8%. Corrected for parental asthma, parental atopy was a weak but significant risk factor. There were minor differences in the impact of parental disease between sensitized and nonsensitized children and between boys and girls. CONCLUSIONS: As risk factors for childhood asthma, there were major differences between parental asthma and parental atopy. Sibling asthma was only a marker of parental disease. Interactions between parental disease and the child's allergic sensitization or gender were not statistically significant. Asthma in both parents conferred a multiplicative risk, whereas the effect of parental atopy was additive, however limited. Asthma and atopy, despite their causal relationship, are separate entities and could be inherited differently. This large, population-based, and well-characterized cohort study does not confirm parent-of-origin effects found in previous studies.

National Category
Environmental Health and Occupational Health
Identifiers
urn:nbn:se:umu:diva-19126 (URN)10.1542/peds.2006-3742 (DOI)17908760 (PubMedID)
Available from: 2009-03-04 Created: 2009-03-04 Last updated: 2016-03-11
3. Sex-specific trends in childhood asthma and wheeze: prevalence and risk factors in Sweden 1996-2006
Open this publication in new window or tab >>Sex-specific trends in childhood asthma and wheeze: prevalence and risk factors in Sweden 1996-2006
(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:umu:diva-3030 (URN)
Available from: 2008-03-17 Created: 2008-03-17 Last updated: 2016-03-11Bibliographically approved
4. Changes in the risk factor pattern of childhood asthma from 1996 to 2006
Open this publication in new window or tab >>Changes in the risk factor pattern of childhood asthma from 1996 to 2006
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(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:umu:diva-3031 (URN)
Available from: 2008-03-17 Created: 2008-03-17 Last updated: 2016-03-11Bibliographically approved

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