| 1. |
- Almqvist, Linnea, 1987-
(författare)
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Asthma epidemiology : prognosis of asthma with onset in childhood and in adulthood
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aim: to update the knowledge on the epidemiology of asthma with onset in childhood and adulthood as well as examine the importance of risk factors in early childhood and clinical characteristics on the incidence and prognosis of asthma.Methods: The thesis is based on the epidemiological research program Obstructive Lung Disease in Northern Sweden (OLIN) studies. Pediatric cohort: recruited in 1996 (age 8y, n=3430, 97% of invited) and followed annually by questionnaire about asthma, allergy and risk factors until 19y and a postal questionnaire at 28y. Clinical examinations included skin prick tests (SPT at 8, 12 and 19y) and spirometry (19y). Adult cohort: 309 adults (age 20–60y) with asthma onset in the last 12 months were recruited 1995-99 and re-examined in 2012-14 (n=205). Structured interviews, spirometry and SPT were performed at recruitment and follow-up and bronchial hyperreactivity (BHR) at recruitment.Results: The asthma incidence rate was 10-13/1000/year in childhood and adolescence and 6/1000/year in young adulthood. Several risk factors in early life were associated with asthma onset in childhood, adolescence and young adulthood, e.g. family history of asthma, <3 months breastfeeding, rhinoconjunctivitis and positive SPT at 8y, while low birthweight, maternal smoking during pregnancy, severe respiratory infections and eczema were associated with onset in childhood and adolescence. Among those with asthma at 8y, 62% still had asthma at 28y and this was associated with positive SPT, rhinoconjunctivitis, severe respiratory infection in childhood, and bronchial hyperreactivity (BHR) in adolescence. Coexistence of asthma, rhinitis and eczema increased by age, especially among those with a positive SPT. However, having all three conditions was uncommon. In the 15y follow-up adult onset asthma, 89% had persistent asthma. Better lung function at recruitment and less severe BHR was associated with remission. Remission rate of adult onset asthma was <1% per year.Conclusion: The incidence of asthma was high during childhood and adolescence and then decreased in young adulthood. Factors in early life that were associated with incident asthma during childhood were still associated with the incidence in adult age. Among those with asthma onset by 8 years, 62%, still had asthma as young adults. The coexistence of asthma, rhinitis and eczema varied from 8 to 28y without following a specific pattern, only a small proportion reported having all three conditions. Remission of adult onset asthma was rare.
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| 2. |
- Andersson, Martin, 1979-
(författare)
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Asthma in school age : prevalence, incidence and remission in relation to environmental determinants
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background In the past half-century, the prevalence of asthma among children and adolescents has risen and asthma has become an important public health challenge in Sweden as well as in many other countries, necessitating further studies on this complex disease and its risk factor pattern. The studies included in this thesis aimed to investigate the clinical expression of childhood asthma over time, to describe the determinants of new-onset and remission of asthma, and to evaluate possible environmental risk factors in northern Sweden.Methods As the result of a repeated questionnaire survey among primary school children aged 7-8 years in three municipalities in the north of Sweden, two pediatric cohorts were formed, one in 1996 (n=3430) and one in 2006 (n=2585). The cohort created in 1996 was followed annually until the age of 19 years. Skin prick testing was performed on children in both cohorts. Lung function and bronchial hyperreactivity testing were carried out in children with asthma in the first cohort. The study participation and retention rates were very high in both cohorts. Among children in the second cohort living in Luleå, the home addresses were assigned to coordinates in a geographical information system (GIS) to evaluate the impact on respiratory health of living near roads with much traffic, which was measured as the number of vehicles daily. We used a validated reported diagnosis of asthma and International Study of Asthma and Allergies in Childhood (ISAAC) questions were incorporated into the questionnaire. A cross-sectional study of children of the same age ten years apart, longitudinal studies on asthma incidence and remission as well as a cross-sectional study on vehicle traffic were performed.Results While children aged 7-8 years in 2006 more often had a physician-diagnosed asthma compared to children of the same age in 1996 (7.4% vs 5.7%, p<0.001), they had less asthma symptoms, especially severe symptoms. In parallel, a more beneficial environment and a more intense treatment with inhaled corticosteroids (ICS) were observed. The explanation for this change in clinical expression probably includes also an increased awareness and diagnosing of asthma. From age 12 years to age 19 years, the cumulative incidence of physician-diagnosed asthma was 7.2% and of current wheeze 22.0%. The risk of new-onset asthma in adolescence was increased among girls, sensitized and those with heredity for asthma. Smoking and home dampness increased the risk for incident wheeze. The risk for both incident asthma and wheeze was inversely related to number of siblings. Among children with current asthma at age 7-8 years, 21% were in remission, 38% had periodic asthma and 41% had persistent asthma at a follow-up at age 19 years. Subjects in remission and with periodic asthma had significantly less airway obstruction and showed less bronchial hyperreactivity compared to subjects with persistent asthma. The probability of asthma remission from childhood to early adulthood was significantly increased by absence of allergic sensitization, male gender and a low asthma severity scoring at age 7-8 years. Sensitization to furred animals was more important as a determinant of both incidence and remission than sensitization to pollen. Living close to roads with high traffic flows, especially with heavy vehicles, was associated with an increased risk for current wheeze. Stratified analyses showed that the effect of traffic on asthma and wheeze was restricted to non-sensitized subjects.Conclusion Asthma onset in adolescence was more common among girls and remission was more common among boys. Children sensitized to furred animals and children with a more severe asthma were risk groups for persistence of asthma. Environmental factors such as smoking and dampness were associated to onset of asthma symptoms during adolescence, and vehicle traffic was associated with asthma symptoms among children also in a small city with relatively low traffic flows. Preventive measures like smoking reduction programs, improvement of damp housing conditions and separation of areas where many children live from heavily trafficked roads could prove to be beneficial.
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| 3. |
- Backman, Helena, 1979-
(författare)
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Lung function and prevalence trends in asthma and COPD
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Asthma and chronic obstructive pulmonary disease (COPD) are common obstructive airway diseases with a substantial burden in terms of morbidity, mortality and costs. Smoking is the single most important risk factor for COPD, and is associated with incident asthma. It is important to know if the prevalence of asthma and COPD is increasing or decreasing in the population in order to effectively allocate health care resources. The definitions of these diseases have varied over time which makes it difficult to measure changes in prevalence. The preferred method is to estimate the prevalence with the same procedures and definitions based on cross-sectional population samples with identical age distributions in the same geographical area at different time points. Measurements of lung function (spirometry) are required to diagnose COPD, and spirometry is used to evaluate disease severity and progress of both asthma and COPD, where observed values are compared to reference values. The most commonly used reference values in Sweden are published during the mid 1980s, and there are few evaluations of how appropriate they are today based on Swedish population samples. The aim of the thesis was to estimate trends in the prevalence of asthma and COPD in relation to smoking habits, and to evaluate and estimate reference values for spirometry.Methods: The project was based on population-based samples of adults from the Obstructive Lung Disease in Northern Sweden (OLIN) studies. Postal questionnaires were sent to large cohorts, recruited in 1992 (n=4851, 20-69 years), 1996 (n=7420, 20-74 years) and 2006 (n=6165, 20-69 years), respectively. The questionnaire included questions on respiratory symptoms and diseases, their comorbidities and several possible risk factors including smoking habits. Structured interviews and spirometry were performed in random samples of the responders to the 1992 and 2006 surveys, of which n=660 (in 1994) and n=623 (in 2009) were within identical age-spans (23-72 years). The trend in asthma prevalence was estimated by comparing the postal questionnaire surveys in 1996 and 2006, and the trend in COPD prevalence was estimated by comparing the samples participating in dynamic spirometry in 1994 and 2009, respectively. The prevalence of COPD was estimated based on two different definitions of COPD. Commonly used reference values for spirometry were evaluated based on randomly sampled healthy non-smokers defined in clinical examinations of participants in the 2006 postal questionnaire (n=501). The main focus of the evaluation was the global lung function initiative (GLI) reference values published in 2012, for which Z-scores and percent of predicted values were analysed. New sex-specific reference values for spirometry were estimated by linear regression, with age and height as predictors. These new OLIN reference values were also evaluated on a sample of healthy non-smokers identified in the population-based West Sweden Asthma Study.Results: Although the prevalence of smoking decreased from 27.4% to 19.1%, p<0.001, between 1996 and 2006, the prevalence of physician-diagnosed asthma increased from 9.4% to 11.6%, p<0.001. The prevalence of symptoms common in asthma such as recurrent wheeze did not change significantly between the surveys or tended to decrease, while bronchitis symptoms such as cough and sputum production decreased significantly. The evaluation of the GLI reference values showed that the predicted values were significantly lower compared to the observed values in Norrbotten, which makes the percent of predicted too high. This was especially true for FVC percent predicted with a mean of 106%. In general, the deviations were more pronounced among women. New OLIN reference values valid for the Norrbotten sample were modelled and showed a high external validity when applied on the sample from western Sweden. The prevalence of moderate to severe COPD decreased substantially over the 15-year period between 1994 and 2009, regardless of definition.Conclusions: In parallel with substantially decreased smoking habits in the population between 1996 and 2006, the prevalence of several airway symptoms decreased while the prevalence of physician-diagnosed asthma increased. These results suggest increased diagnostic activity for asthma, but may also suggest that the asthma prevalence has continued to increase. In contrast to asthma, the prevalence of COPD tended to decrease and moderate to severe COPD decreased substantially. The continuous decrease in smoking in Sweden during several decades prior to the study period is most likely contributing to these results. The evaluation of reference values showed that the GLI reference values were lower than the observed spirometric values in the population, especially for women, why the new up-to date reference values may be of importance for disease evaluation in epidemiology and in the health care as well.
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| 4. |
- Bjerg Bäcklund, Anders, 1982-
(författare)
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Epidemiology of asthma in primary school children
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 5. |
- Bunne, Joakim, 1987-
(författare)
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Allergic sensitization among schoolchildren in northern Sweden : time trends, risk factors and relation to asthma, allergic rhinitis and lung function.
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Asthma and allergic rhinitis are common chronic diseases of childhood.Their prevalence has increased globally in the 20th century, with regionally diverging trends in recent years. Allergic sensitization (AS) is strongly associated with asthma and allergic rhinitis (AR), with similar trends over time and uncertainty of development in recent years. AS increases in childhood until young adulthood. Risk factors for AS are not as well characterized as for asthma and AR, and important aspects of the relation between AS and disease are not known. This includes why some sensitized children do not develop disease and how common this is in a longitudinal perspective. While many studies have assessed AS in the first years of life, fewer have focused on school age, and none have focused on the effect of age at onset of AS. Further, the association between AS and lung function is unknown.Aims: To assess time trends in prevalence, incidence and factors associated with AS in schoolchildren. Further, to assess the association between AS and asthma, allergic rhinitis and lung function, with special interest in age at onset of sensitization.Methods: Children in grades 1 and 2 (median age 8 years) in two municipalities in northern Sweden were invited to a questionnaire study of allergic diseases and skin prick tests to common aeroallergens in 1996. The cohort was reassessed at 12 and at 19 years also including spirometry. Identical methods were used to recruit a second and third cohort in 2006 and 2017.Results: The prevalence of AS at 8 years was 21% (1996), 30% (2006) and 30% (2017). Patterns of sensitization and risk factors for sensitization were similar. In the second cohort, the incidence between 8-12 years of 18% and prevalence of 41% at 12 years were higher than in the first cohort. Compared with later onset, sensitization ≤8 years was more strongly associated with asthma and allergic rhinitis at 19 years. AS was not independently associated with lung function at 19 years.Conclusions: In northern Sweden, the increase in allergic sensitization at age 8 years between 1996 and 2006 has halted in recent years. The increase between the first two cohorts was seen also at age 12 years. Age at onset of allergic sensitization impacts development of asthma and allergic rhinitis until 19 years. Despite an association with asthma, sensitization does not affect lung function at 19 years.
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| 6. |
- Hedman, Linnea, 1979-
(författare)
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Epidemiological studies of asthma and allergic diseases in teenagers : methodological aspects and tobacco use
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Parental reports are often used in studies of asthma and allergic diseases in children. A change in respondent from parent to index subject usually occurs during adolescence. Little is known about the effects this change in method might have on the outcomes of a longitudinal study. Smoking is a major cause of respiratory symptoms among adults and environmental tobacco smoke (ETS) is a risk factor for asthma among children. Less is known about these associations among teenagers. In order to improve prevention of smoking, it is important to identify populations at risk of becoming smokers. The aim of this thesis were to 1) evaluate the methodological change from parental to self-completion of a questionnaire about asthma and allergic diseases, and 2) to study determinants for, and respiratory health effects of ETS and personal smoking in teenagers.In 1996, a longitudinal study of asthma and allergic diseases among schoolchildren started within the Obstructive Lung Disease in Northern Sweden (OLIN) studies. All children in first and second grades (aged 7-8 years) in three municipalities, Luleå, Kiruna and Piteå (n=3,525) were invited and 97% participated by parental completion of a questionnaire. The cohort has been followed with annual questionnaires until age 16-17 years and with high participation rates (>91%). From age 12-13 years, the teenagers were the respondents and questions about their tobacco use were included. In addition to the questionnaire completed by the teenagers at age 13-14 years, a questionnaire was also distributed to a random sample of 10% of the parents and 294 participated (84%). The parents and the teenagers reported a similar prevalence of asthma, respiratory symptoms, rhinitis, eczema and environmental factors. Two statistically significant differences were found: the teenagers reported a higher prevalence of wheezing during or after exercise (14% vs 8%, p<0.05), and having a dog in the home in the last 12 months (42% vs 29%, p<0.001). Answer agreement between parents and teenagers on questions about asthma was almost perfect with kappa values of 0.8-0.9. Corresponding kappa values for questions about respiratory symptoms and rhinitis were 0.3-0.6 and for eczema 0.5-0.6. Agreement about environmental factors varied from 0.2-0.9. Kappa values for parental smoking were 0.8-0.9. The risk factor pattern for allergic diseases was similar regardless of respondent, ie parent or teenager.The prevalence of smoking increased from 3% at 12-13 years to 6% at 14-15 years. Smoking was more common among girls, while the use of snus was more common among boys. Significant risk factors related to smoking among teenagers were smoking family members, female sex and living in an apartment. Having physician-diagnosed asthma did not prevent the teenagers from becoming smokers. Factors related to using snus were a smoking mother and male sex. Daily smokers aged 16-17 years (9%) reported a significantly higher prevalence of wheezing and physician-diagnosed asthma compared to non-smokers. There was a significant dose-response association with higher prevalence of wheeze among those who smoked ≥11 cigarettes per day compared to those who smoked ≤10 per day. In multivariate analyses, maternal environmental tobacco smoke exposure was a significant risk factor for ever wheeze and physician-diagnosed asthma at age 16-17 years, while daily smoking was a risk factor for current wheeze.In conclusion, the methodological change of questionnaire respondent from parent to index subject did not substantially alter the findings of this longitudinal study. There were significant sex differences in the tobacco use: smoking was more common among girls and snus was more common among boys. The most important factor related to tobacco use was presence of family members who smoke. Both maternal ETS exposure and personal smoking was associated with asthma and wheeze in adolescence. ETS was associated with lifetime symptoms but daily smoking was more strongly associated with current symptoms.
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| 7. |
- Kalm-Stephens, Pia, 1959-
(författare)
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Development of allergic and respiratory symptoms in adolescence and early adulthood : Risk factors and gender differences
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Asthma and allergic diseases have increased in prevalence for several decades and affect a substantial number of individuals in everyday life, as well as their families and public healthcare resources. Subjects with asthma report impaired self-rated health. Fractional exhaled nitric oxide (FeNO) is a marker of type 2 inflammation in the airways and higher levels may precede the development of allergic and respiratory disease.Aims: To investigate the development of allergic and respiratory symptoms in adolescence and early adulthood, and related baseline risk factors. Further, to study self-rated health in young adults with reported asthma.Methods: A total of 959 schoolchildren completed a standardized respiratory questionnaire and underwent lung function and FeNO measurements at baseline (12–15 years; early adolescence). Four (late adolescence) and sixteen (early adulthood) years later, 921 (96%) and 502 (52%) of these individuals completed a similar questionnaire. A total of 491 subjects participated in all three examinations. Nineteen clinically assessed non-asthmatic subjects with elevated FeNO and 28 control subjects with low FeNO and without symptoms of asthma or allergy in early adolescence were identified. Their FeNO, IgE sensitization, airway responsiveness, and inflammatory markers in blood and sputum were measured.Results: The main finding was that higher FeNO in early adolescence was associated with an increased risk of developing allergic symptoms to cat and dog, but not pollen allergens, during adolescence. Gender-stratified data showed that obesity at baseline in girls and an atopic constitution in boys were associated with increased risk of developing wheeze during adolescence. The prevalence of asthma and wheeze had increased in early adulthood, but the increase was significant only in females. Reduced lung function at baseline in females and higher FeNO in males were associated with an increased risk of incident asthma sixteen years later. The increase in allergic symptoms during this period was significant but without sex differences. Asthmatic females rated their health worse than non-asthmatic females, a difference not observed in males. Non-asthmatic adolescents with higher FeNO at baseline were to a higher extent sensitized, had more reactive airways, higher blood eosinophil counts, and lower systemic activation of neutrophils, compared with controls.Conclusions: It is important to detect risk factors for the development of allergic and respiratory diseases at an early stage to optimize health and wellbeing. Gender differences in respiratory development, associated risk factors, and treatment of respiratory symptoms must be taken into account.
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| 8. |
- Patelis, Antonios, 1980-
(författare)
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IgE sensitization against food allergens : Natural history, relation to airway inflammation and asthma
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: According to recent studies in children, IgE sensitization not only against perennial allergens, but also against food allergens, is related to asthma risk and increased airway inflammation. During the last decade, a new technique for IgE determination based on allergen components has become available, but its use in epidemiological studies has been limited.Aims: To investigate the relationship between the pattern of IgE sensitization to allergen components and the prevalence of asthma, airway inflammation and hyperresponsiveness in a population-based setting. To examine the relationship of IgE sensitization to allergen extract, and airway inflammation, airway hyperresponsiveness and blood eosinophilia in asthmatics. To examine the natural history of IgE sensitization to food allergens in adults. To compare extract-based and component-based IgE measurements in relation with new-onset respiratory disease and airway inflammation and hyperresponsiveness.Methods: The present thesis is based on cross-sectional and longitudinal analyses of the adult, the population-based study ECRHS (European Community Health Survey) and a cross-sectional, observational study of young subjects with asthma. IgE sensitization was examined by means of both extract-based and component-based tests. Airway inflammation was assessed by exhaled NO and airway hyperresponsiveness with methacholine test. Results: IgE sensitization to food allergens independently related to increased airway inflammation in both a population-based study and a study of asthmatics. Furthermore, a relation was found with increased blood eosinophils in asthmatics. The decrease in prevalence of IgE sensitization against food allergens during a 9-year follow-up was larger than the decrease of aeroallergens. Subjects with IgE sensitization to both cat extract and components showed more frequent airway inflammation, greater bronchial responsiveness and higher likelihood of developing asthma and rhinitis than subjects with IgE sensitization only to cat extract. Conclusions: The presence of IgE antibodies against food allergens was independently associated with airway and systemic inflammation. Both aeroallergens and food allergens should be examined in order to understand the signaling of local and systemic inflammation in asthma. Prevalence of IgE sensitization to food decreased in adults to a larger extent than IgE sensitization against aeroallergens. Measurement of IgE sensitization to cat allergen components appears to have a higher clinical value than extract-based measurement
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| 9. |
- Schyllert, Christian, 1983-
(författare)
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Social determinants in asthma : population-based studies on asthma and respiratory symptoms in relation to occupation, occupational exposure and socioeconomic status
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Asthma is one of the most common chronic obstructive airway diseases among children and adults, with a prevalence between 6-11% in European countries. It is also the most common work-related occupational respiratory disease. There are different methods to classify occupational exposure and, even though there is no clear consensus on which method is the most accurate, the single-item question on exposure to the composite measure vapour, gas, dust or fumes (VGDF) is commonly used in epidemiological research. Low socioeconomic status is associated with asthma and also behavioural factors such as smoking and over-weight, which by themselves are risk factors for asthma. Socioeconomic status is, however, truly a multifaceted concept and using only one measure does not encompass its entire effect on health-related outcomes. Asthma does also have a negative impact on the quality of life among adolescents: they report less physical fitness compared to their peers and more school absenteeism due to respiratory symptoms. Still, research on whether childhood asthma has any impact on socioeconomic status in young adulthood is scarce.Aim: The overall aim is to study social determinants of health such as socioeconomic status, occupation and occupational exposure and their relationship with asthma and respiratory symptoms among adults and further, to evaluate if asthma during childhood or adolescence is associated with social determinants in young adulthood.Method: This thesis includes four papers based on data from the Obstructive Lung Disease in Northern Sweden (OLIN) studies. Papers I-III are cross-sectional studies among adults; a structured interview from clinical examinations between 2002-04 (paper I, n=4036) and postal questionnaire surveys from 2006 (paper II, n=9992) and 2016 (paper III, n=6854) with the addition of register-based data in paper III. Paper IV is a longitudinal prospective cohort study; the first OLIN paediatric cohort followed from 7 to 19 years of age and a postal questionnaire follow-up at ages 27-28 in 2015 (n=2017). Asthma was defined as physician diagnosis (paper I) together with respiratory symptoms (paper II-IV) or use of asthma medication (paper IV). In paper IV asthma was further categorized based on age of onset and p v and adolescence. Main or longest held occupation was used to categorize occupational and socioeconomic groups. In papers III and IV additional measures of socioeconomic status were included; educational level (papers III and IV) and income (paper III). In all papers, occupational exposure to vapour and/or gas, dust and fumes (VGDF or GDF) were taken into consideration and in paper I further divided into subgroups based on a detailed questionnaire on occupational exposure.Results: In paper I we found that the association between occupational exposure to VGDF and asthma and rhinitis was driven by the component of chemicals rather than dusts. In paper II, the ISCO-based manual Swedish Standard Classification of Occupations (SSYK) and the manual Socioeconomic classification (SEI), could both identify occupational and socioeconomic groups at risk for respiratory symptoms and asthma, while the older ISCO-based manual Nordic Classification of Occupations (NYK) was not as sensitive.In paper III, behavioural risk factors for respiratory symptoms and asthma such as smoking and obesity and, occupational exposure to GDF were associated with low educational level. Interaction analyses between income level and sex revealed different patterns among women and men. Among women, low income was associated with all respiratory symptoms as well as asthma, while among men only with productive cough.In paper IV, early onset asthma was associated with lower educational level in young adulthood, especially not continuing after compulsory school. Further, those with asthma during childhood or adolescence did not seem to refrain from smoking at age 19, nor did they as young adults seem to avoid occupations with known or expected exposure to GDF.Conclusions: Increased automation in industries have decreased the number of manual workers in industries with typically dirty tasks, meaning that the interrelationships between the subgroups included in VGDF may have changed. This may also affect the meaning of occupational exposure to VGDF, at least with regard to asthma and rhinitis, and according to our findings exposure to the component of chemicals may be the most important. We also found that the use of an ISCO-based manual (SSYK) as well as socioeconomic classification based on job-title (SEI) can be useful and easily applicable tools to identify occupational and socioeconomic groups at risk for respiratory symptoms and asthma. Further, low socioeconomic status is associated with respiratory vi symptoms and asthma. It seems as these associations relies more on low income than low educational level. Low educational level as well as low income are furthermore related to known behavioural risk factors for respiratory symptoms and asthma such as obesity, smoking and, also potentially modifiable risk factors as occupational exposure to gas dust or fumes. Having a persisting asthma since childhood is associated with lower educational level as a young adult. This may, in turn, be related with behavioural risk factors as discussed above and, there were no indications that those with child or adolescent asthma refrained from smoking at age 19. Neither did they in young adulthood avoid occupations with known or expected exposure to gas, dust or fumes, such as manufacturing, construction and transportation work. To conclude, our results indicate a vicious circle with regard to the relationship between the studied social determinants of health and asthma and respiratory symptoms.
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| 10. |
- Strinnholm, Åsa, 1962-
(författare)
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Food hypersensitivity among schoolchildren : prevalence, Health Related Quality of Life and experiences of double-blind placebo-controlled food challenges
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: The prevalence of reported food hypersensitivity among children has increased in Western countries. However, the prevalence varies largely due to differences in methods used in different studies. Double-blind placebo-controlled food challenge (DBPCFC) is the most reliable method to verify or exclude food hypersensitivity. The use of double-blind food challenges is increasing in clinical praxis, but since the method is time- and resource consuming it is rarely used in population-based cohort studies. There is a lack of knowledge on how adolescents and mothers experience participation in double-blind placebocontrolled food challenges and to what extent the food is reintroduced after a negative challenge. While several studies have described the impact of IgEmediated food allergy on Health-Related Quality of Life (HRQL), few studies have described HRQL among children with other food hypersensitivity phenotypes.Aim: The aim of this thesis was to estimate the prevalence of reported food hypersensitivity, associated risk factors, and symptom expressions among schoolchildren. We also examined HRQL among children with total elimination of cow's milk, hen’s egg, fish or wheat due to food hypersensitivity as a group compared with children with unrestricted diet, and after we categorised the children with eliminated foods into different phenotypes of FHS. Finally, adolescents' and mothers' experience of DBPCFC was examined as well if the food had been reintroduced.Methods: Three studies were based on the Obstructive Lung Disease in Northern Sweden (OLIN) paediatric cohort II. The cohort was recruited in 2006 when all children in first and second grade (7-8 years) in three municipalities in Norrbotten were invited to a parental questionnaire study and 2,585 (96% of invited) participated. The questionnaire included questions about food hypersensitivity, asthma, rhinitis, eczema and possible risk factors. The children in two municipalities were also invited to skin prick testing with 10 airborne allergens, and 1,700 (90%) participated. Paper I is based on this initial survey of the cohort. Four years later, at age 11-12 years, the cohort was followed up using the same methods and with the same high participation rate. At the follow-up, 125 children (5% of the cohort) reported total elimination of cow's milk, hen's egg, fish or wheat due to food hypersensitivity. These children were invited to a clinical examination and to complete a generic (KIDSCREEN-52) and a diseasespecific HRQL questionnaire (FAQLQ-TF) (n=75). Based on the clinical examination the children were categorised into different phenotypes of food hypersensitivity: current food allergy, outgrown food allergy and lactose intolerance. In addition, a random sample of children with unrestricted diet from the same cohort, answered the generic questionnaire (n=209). Paper II is based on this HRQL study. Children categorised as having current food allergy were invited to a further evaluation including DBPCFC. Eighteen months after the challenges, these children were interviewed about their experiences during and after the challenge (n=17). Paper III is based on these interviews. Paper IV was based on interviews with mothers to children referred to a paediatric allergy specialist for evaluation of food allergy using DBPCFC (n=8). In the two interview studies results were analysed using qualitative content analysis.Results: At age 7-8 years, the prevalence of reported food hypersensitivity was 21%. Food hypersensitivity to milk, egg, fish, wheat or soy was reported by 10.9% and hypersensitivity to fruits or nuts by 14.6%. The most common essential food to trigger symptoms was milk, reported by 9%. The most frequently reported food induced symptoms, were oral symptoms mainly caused by fruits, followed by gastrointestinal symptoms mainly caused by milk. The risk factor pattern was different for food hypersensitivity to milk compared to hypersensitivity to other foods. No significant difference in distribution in generic or disease-specific HRQL was found among children with reported total elimination of milk, egg, fish and/or wheat due to FHS compared to children with unrestricted diet. However, a trend indicated that the disease-specific HRQL was most impaired among children with current food allergy compared to children with outgrown food allergy and lactose intolerance. The proportion of poor HRQL defined as ≥75 percentile was significantly higher among children with current food allergy than the other phenotypes. A DBPCFC was an opportunity for the adolescents and the mothers to overcome the fear of reactions to food that had been eliminated for a long time. After the challenge, when the food was partially or fully reintroduced, socializing became easier and both adolescents and mothers experienced more freedom regarding food intake. A negative challenge was not consistently associated with reintroduction of the food. Reasons for reintroduction failure were fear of allergic reactions, that the adolescent did not like the taste of the food, or that living with an elimination diet was considered as normal. Conclusion In this population-based study, one in five of children at age 7-8 years reported food hypersensitivity to any food. The generic HRQL was similar among children with and without food hypersensitivity. However, poor disease-specific HRQL was more common among children with current food allergy compared to children with other FHS phenotypes. If the tested food was reintroduced after a DBPCFC, both adolescents and mothers described a changed life with less fear, and that life had become easier regarding meal preparations and social events. As reintroduction failure was present despite a negative food challenge, follow-ups and evaluations of food reintroduction should be performed independent of the outcome of a food challenge.
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