Changes in prevalence of asthma and allergy in Swedish school children over almost three decades and factors reducing risk of allergy

• Main Author: Hicke-Roberts, Anna
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2021
• Subjects: allergi; barn; epidemiologi; riskfaktorer; skyddande faktorer; Kiruna
• Online Access: http://hdl.handle.net/2077/68704

ABSTRACT Background: Asthma and allergy are one of the most common chronic diseases among children. The prevalence of allergic diseases increased dramatically during the last decades of the twentieth century. The reason behind this increase is still not fully understood. Aim: The aim of the thesis was to investigate changes over time in the prevalence of asthma and allergy in two Swedish towns, and to identify protective and risk factors for allergy development. Methods: Data were obtained from two studies: a population-based cross-sectional study that was used in all four papers, and in paper III results from a birth cohort study was added. The cross-sectional study (N=1029) was performed in 2007 and prevalence data were compared with two previous cross-sectional studies conducted in 1979 and 1991. All three studies were based on questionnaires with the same set of questions on asthma and allergy, and the children were of the same age and from the same two Swedish towns: Mölndal/Gothenburg and Kiruna. Questions on dietary habits and food allergy were added in 2007 study. The birth cohort study (N=249), used in paper III, recruited children from Västra Götaland county. The children were recruited at birth, between 1998 and 2005, and they were clinically assessed at the age of 8-9 years. Results: Paper I: The prevalence of asthma were 2.5% (1979), 5.7% (1991) and 7.1% (2007), allergic rhino-conjunctivitis: 5.5% (1979), 8.1% (1991) and 11.1% (2007), eczema 7.1% (1979), 18.3% (1991) and 19.7% (2007) respectively. Allergic rhino-conjunctivitis continued to increase from 1979 to 2007, while asthma and eczema levelled off between 1991 and 2007. Having both parents born abroad was a protective factor for developing allergy. Paper II: Hand-dishwashing decreased the risk of allergy (odds ratio 0.57; 95% confidence interval 0.37-0.85). The risk was reduced in a dose-response pattern if the child was also served fermented food, and if the family bought food directly from a farm. Paper III: Keeping cats and dogs during the ...