Decreased importance of environmental risk factors for childhood asthma from 1996 to 2006

Is asthma in children still increasing? 20-year prevalence trends in northern Sweden

BACKGROUND

In the present study, we describe prevalence trends of asthma and investigate the association with asthma symptoms, use of asthma medication, and asthma severity among 8-year-old children in Norrbotten, Sweden in 1996, 2006, and 2017.

METHODS

Within the Obstructive Lung Disease in Northern Sweden (OLIN) studies, three pediatric cohorts were recruited in 1996, 2006, and 2017 respectively. Identical methods were used; all children in first and second grade (median age 8 years) in three municipalities were invited to a parental questionnaire survey, completed by n = 3430 in 1996 (97% participation), n = 2585 in 2006 (96%), and n = 2785 in 2017 (91%). The questionnaire included questions about respiratory symptoms and diagnosis, treatment, and severity of asthma.

RESULTS

The prevalence of wheezing was stable during the study, 10.1% in 1996; 10.8% in 2006; and 10.3% in 2017, p = .621, while physician-diagnosed asthma increased: 5.7%, 7.4%, and 12.2%, p < .001. The use of asthma medication in the last 12 months increased: 7.1%, 8.7%, and 11.5%, p < .001. Among children diagnosed with asthma, the prevalence of asthma symptoms, the impact on daily life, and severe asthma decreased, while the use of inhaled corticosteroids increased from 1996 until 2017.

CONCLUSION

The prevalence of wheezing was stable among 8-year-old in this area from 1996 to 2017, while the prevalence of physician-diagnosed asthma doubled but without an increase in asthma morbidity. The increase of physician-diagnosed asthma without a coincident increase in asthma morbidity can partly be explained by more and earlier diagnosis among those with mild asthma.

The frequency of sleep-disordered breathing in preschool children with asthma and its effects on control of asthma

CONCLUSION

The frequency and score of SDB were higher in patients with uncontrolled asthma. Frequency and score of SDB were significantly affected by the severity of asthma. SDB must be evaluated in preschool children with uncontrolled asthma.

CONCLUSION

Sleep-disordered breathing (SDB) is more common in asthmatic patients than in non-asthmatic persons, and SDB affects negatively to control asthma. A limited number of studies are discovered on the effect of SDB in preschool asthmatic children. In this study, we aimed to investigate the prevalence of SDB and its effect on control and severity of asthma in preschool children. A pediatric sleep questionnaire was completed by parents of asthmatic children. Patients who received a score of 0.33 or higher were diagnosed with SDB. Control and severity of asthma was assessed by a pediatric allergy specialist based on the Global Initiative for Asthma (GINA) criteria. The study included 249 patients, with a mean±SD age of 4.37±1.04 (range: 2-5.9) years; 69% were boys; 56.6% children had uncontrolled asthma and 28.7% had SDB. The SDB score was significantly different between controlled and uncontrolled asthma (0.19 vs 0.28; P < 0.001). The frequency of uncontrolled asthma in patients with and without SDB was 74.3% and 49.4%, respectively (P < 0.010). Based on the severity of asthma, the frequency of SDB among patients with mild, moderate, and severe asthma was 23.4%, 35.2%, and 47.4%, respectively (P = 0.010).

Factors Associated with the Development of Childhood Asthma in Japan: A Nationwide Longitudinal Study

INTRODUCTION

Many environmental factors are related to the development of asthma. However, the key factors of childhood asthma onset have not been sufficiently elucidated. Further, low-weight births have increased in Japan. The aim of this study was to examine the risk factors for the incidence of childhood asthma and to evaluate whether these risk factors differ according to birth weight in Japan.

METHODS

We used the National Longitudinal Survey from 2001 to 2010. Multiple logistic regression analyses were conducted to determine the effects of gender, birth weight, single vs. multiple births, birth order, nutrition, keeping pets in the home, place of residence, annual household income, and parent ages, smoking behaviors, and educational backgrounds on asthma-related hospital visits.

RESULTS

Overall, 45,060 children were analyzed. The rate of cumulative hospital visits until age 10 was 18.9%. Birth weight < 2500 g (adjusted odds ratio [AOR] = 1.14, 95% confidence interval [CI] 1.03-1.26), being a boy (AOR = 1.27, 95% CI 1.21-1.33), having older siblings (AOR = 1.07, 95% CI 1.02-1.14), parental smoking behavior, mother`s age, and low household income (AOR = 1.17, 95% CI 1.10-1.24) were associated with asthma-related hospital visits.

DISCUSSION

Parental smoking behavior is a key risk factor for the development of asthma. Among low birth weight infants, being a boy, having older siblings, and father`s smoking behavior were predictive factors for the development of asthma. However, low birth weight was not associated with the development of asthma after 6 years of age.

Lower respiratory tract infections appear to be the most important risk factor for current asthma in subarctic schoolchildren

AIM

The aim of this study was to identify possible risk factors for current asthma revealed by two studies in Northern Norway in 1985 and 2008 and to evaluate these factors contributing to the increased prevalence of asthma over these 23 years.

METHODS

As part of the 'Asthma and allergy study among schoolchildren in Nordland county' we performed a case-control study (70.0% attendance) comparing 153 children with current asthma (cases) to their non-asthmatic controls. The results from this 2008 study were compared to a similar case-control study (93.2% attendance) performed in 1985 based on 62 current asthmatics.

RESULTS

In 1985, the most important risk factors for current asthma were repeated lower respiratory tract infections (LRTIs) with adjusted odds ratio (aOR) 52.11, together with urticaria ever and atopic disease in the family. In 2008, the most important risk factors were food allergy with aOR 7.06, LRTIs during the first three years of life with aOR 5.80 and hospitalisation caused by LRTIs.

CONCLUSION

In both studies, LRTI was the most important risk factor for current asthma. Whether or not LRTIs have contributed to the increased asthma prevalence in this population over 23 years remains unresolved.

Characterization of sensitization to furry animal allergen components in an adult population

BACKGROUND

There are paucity of data on sensitization to furry animal allergen components in adults. Furry animals are major sensitizers and contributors to asthma burden in northern Europe and North America.

OBJECTIVE

To characterize sensitization patterns to furry animal allergen components in Swedish adults.

METHODS

Based on the West Sweden Asthma Study, a random population (n = 1103) and an asthma sample (n = 769) were tested for allergen sensitization using Phadiatop^® . Those with IgE ≥ 0.35 kU_A /L were tested for cat (Fel d 1, 2, and 4), dog (Can f 1, 2, 3, and 5), and horse (Equ c 1) allergen component sensitization. We defined allergen component poly-sensitization patterns, identified data-driven sensitization clusters, described component sensitization overlaps, and assessed determinants of sensitization patterns.

RESULTS

The prevalence of allergen component sensitization ranged from 0.8% for Fel d 2 and Can f 3 to 8.9% for Fel d 1. The most common dog component was Can f 5 (3.6%); 2.1% were sensitized to Equ c 1. Those sensitized to Fel d 2 and Fel d 4 were commonly sensitized to Fel d 1. The most common dog component overlap was between Can f 1/Can f 2 and Can f 5. Mono-sensitization was 5.6%, double sensitization 1.5% and poly-sensitization 2.1%. Sensitization was always higher in the asthma than in the random sample. Three sensitization clusters were derived, namely non-sensitized (90% in random vs 66% in asthma sample); Fel d 1-driven sensitized (7% vs 19%); and multi-sensitized (3% vs 15%). Key determinants of sensitization were gender, age, raised on a farm, family history of allergy or asthma, smoking, and occupational exposure to dust or fumes.

CONCLUSIONS & CLINICAL RELEVANCE

Fel d 1 and Can f 5 are the most common cat and dog components sensitization in this adult Swedish population. Mono-sensitization is more common than poly-sensitization. This detailed characterization highlights the current distribution of furry animal allergen components in Swedish adults, and their impact on clinical outcomes of asthma will be further explored.

The impact of maternal smoking during pregnancy on childhood asthma: adjusted for exposure misclassification; results from the National Health and Nutrition Examination Survey, 2011-2012

PURPOSE

We sought to examine the association between childhood asthma and self-reported maternal smoking during pregnancy (MSDP) after adjusting for a range of exposure misclassification scenarios using a Bayesian approach that incorporated exposure misclassification probability estimates from the literature.

METHODS

Self-reported MSDP and asthma data were extracted from National Health and Nutrition Examination Survey 2011-2012. The association between self-reported MSDP and asthma was adjusted for exposure misclassification using a Bayesian bias model approach.

RESULTS

We included 3074 subjects who were 1-15 years of age, including 492 asthma cases. The mean (SD) of age of the participants was 8.5 (4.1) and 7.1 (4.2) years and the number (percentage) of female was 205 (42%) and 1314 (51%) among asthmatic and nonasthmatic groups, respectively. The odds ratio (OR) for the association between self-reported MSDP and asthma in logistic regression adjusted for confounders was 1.28 (95% confidence interval: 0.92, 1.77). In a Bayesian analysis that adjusted for exposure misclassification using external data, we found different ORs between MSDP and asthma by applying different priors (posterior ORs 0.90 [95% credible interval {CRI}: 0.47, 1.60] to 3.05 [95% CRI: 1.73, 5.53] in differential and 1.22 [CRI 95%: 0.62, 2.25] to 1.60 CRI: 1.18, 2.19) in nondifferential misclassification settings.

CONCLUSIONS

Given the assumptions and the accuracy of the bias model, the estimated effect of MSDP on asthma after adjusting for misclassification was strengthened in many scenarios.

Association of Electronic Cigarette Use With Smoking Habits, Demographic Factors, and Respiratory Symptoms

IMPORTANCE

There is an ongoing debate about whether electronic cigarettes (e-cigarettes) are the solution to the tobacco epidemic or a new public health threat. Large representative studies are needed to study e-cigarette use in the general population, but hardly any have been published.

OBJECTIVES

To estimate the prevalence of e-cigarette use and to investigate the association of e-cigarette use with smoking habits, demographic factors, and respiratory symptoms.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional, population-based study of random samples of the population, performed within the Obstructive Lung Disease in Northern Sweden (OLIN) study and West Sweden Asthma Study (WSAS). The same validated questionnaire including identical questions was used in OLIN and WSAS. In 2016, OLIN and WSAS conducted postal questionnaire surveys in random samples of adults aged 20 to 75 years. In OLIN, 6519 participated (response rate, 56.4%); in WSAS, 23 753 participated (response rate, 50.1%).

MAIN OUTCOMES AND MEASURES

Electronic cigarette use, smoking habits, and respiratory symptoms.

RESULTS

Of 30 272 participants (16 325 women [53.9%]), 3897 (12.9%) were aged 20 to 29 years; 4242 (14.0%), 30 to 39 years; 5082 (16.8%), 40 to 49 years; 6052 (20.0%), 50 to 59 years; 6628 (21.9%), 60 to 69 years; and 4371 (14.4%), 70 to 75 years. The number of current smokers was 3694 (12.3%), and 7305 (24.4%) were former smokers. The number of e-cigarette users was 529 (2.0%), and e-cigarette use was more common among men (275 of 12 347 [2.2%; 95% CI, 2.0%-2.5%]) than women (254 of 14 022 [1.8%; 95% CI, 1.6%-2.0%]). Among current smokers, 350 of 3566 (9.8%; 95% CI, 8.8%-10.8%) used e-cigarettes compared with 79 of 6875 (1.1%; 95% CI, 0.9%-1.3%) in former smokers and 96 of 15 832 (0.6%; 95% CI, 0.5%-0.7%) in nonsmokers (P < .001). Among e-cigarette users who answered the survey question about cigarette-smoking habits (n = 525), 350 (66.7%; 95% CI, 62.7%-70.7%) were current smokers, 79 (15.0%; 95% CI, 11.9%-18.1%) were former smokers, and 96 (18.3%; 95% CI, 15.0%-21.6%) were nonsmokers (P < .001 for trend). In a regression analysis, e-cigarette use was associated with male sex (odds ratio [OR], 1.35; 95% CI, 1.12-1.62); age groups 20 to 29 years (OR, 2.77; 95% CI, 1.90-4.05), 30 to 39 years (OR, 2.27; 95% CI, 1.53-3.36), 40 to 49 years (OR, 1.65; 95% CI, 1.11-2.44), and 50 to 59 years (OR, 1.47; 95% CI, 1.01-2.12); educational level at primary school (OR, 1.99; 95% CI, 1.51-2.64) and upper secondary school (OR, 1.57; 95% CI, 1.25-1.96); former smoking (OR, 2.37; 95% CI, 1.73-3.24); and current smoking (OR, 18.10; 95% CI, 14.19-23.09). All respiratory symptoms were most common among dual users and former smokers and nonsmokers who used e-cigarettes.

CONCLUSIONS AND RELEVANCE

Use of e-cigarettes was most common among smokers, and dual users had the highest prevalence of respiratory symptoms. On a population level, this study indicates that the present use of e-cigarettes does not adequately serve as a smoking cessation tool.

Association of Infant Eczema with Childhood and Adult Asthma: Analysis of Data from the 1958 Birth Cohort Study

The influence of early life exposures on later life disease has for some time provided clues to modifiable risk factors of disease. The “atopic march” is thought to play a role in the progression of allergic diseases and may offer an opportunity to lower asthma’s health and socioeconomic burden, although evidence remains controversial. We aimed to examine the relationship between early life eczema and asthma later in life. Using the National Child Development Study, we examined infant eczema and childhood and adult asthma. Data related to asthma or wheezing bronchitis were available for 13,503 (73%; 95% CI 72–74), 11,503 (61%; 95% CI 60–61), 12,524 (68%; 95% CI 67–69), 11,194 (60%; 95% CI 60–60), 9377 (51%; 95% CI 51–51), and 9760 (53%; 95% CI 52–53) subjects at ages 11, 16, 23, 33, 44, and 50 years, respectively. Logistic regression models were fitted to examine each wave separately before and after adjusting for a range of potential confounders. Generalised estimating equation (GEE) methods were undertaken to examine the associations after pooling all data from questionnaires. The prevalence of self-reported asthma in those that had previously reported infant eczema ranged from 1.0%; 95% CI 0.9–1.4 (age 44 years) to 2.2%; 95% CI 2.1–2.3 (age 33 years). Participants with infant eczema had a 2–3-fold increased risk of reporting asthma in childhood and adulthood; this was 1.6 times at age 44 years when using spirometry measures. Similar effect sizes were observed in the GEE models when considering all participants (OR 2.9; 95% CI 2.6–3.2). Childhood and adult asthma were consistently associated with infant eczema both by using the self-reported data and lung measures.

Birth decade affects the sensitization pattern and asthma risk in Finnish adult population

We have previously shown that sensitizations to several types of allergens distinguish subjects with and without adult-onset asthma in Finland. The aim was to analyze how age affects sensitization and asthma risk. We used previous population-based case-control data (N=456) from Finnish adult asthma patients with one or two matched controls. Asthma was diagnosed based on a typical history of asthmatic symptoms and lung function tests. Allergic sensitization was determined by skin prick test (SPT) to 17 aeroallergens. Information on demographics was obtained by a questionnaire. Sensitization to more than one allergen type and the number of positive SPT reactions associated with younger age and asthma. Atopic subjects aged 65 and above were characterized by sensitization to only one to two allergens, with very few animal danders and without an association with asthma. Multiple sensitizations and animal dander sensitization are more common among Finnish asthmatic adults aged under 56 than among older asthmatics. Cohort studies are needed to understand timing of host-environmental interactions behind this.

Self-Reported Allergic Rhinitis and/or Allergic Conjunctivitis Associate with IL13 rs20541 Polymorphism in Finnish Adult Asthma Patients

BACKGROUND

Our aim was to observe factors associated with IL13 rs20541 polymorphism and other factors with or without allergic comorbidities such as subject-reported allergic rhinitis (AR) and/or allergic conjunctivitis (AC) symptoms in adult asthmatics.

METHODS

A population-based sample of Finnish adult asthma patients (n = 1,156) and matched controls (n = 1,792) filled in a questionnaire. Asthma was diagnosed based on a typical history of asthma symptoms and lung function tests. Skin prick tests with 17 aeroallergens and blood tests including analysis of interleukin 13 (IL13) rs20541 (G/A) genotypes were performed for a subsample (n = 193).

RESULTS

The proportion of asthmatics reporting AR was 61.9% and reporting AC was 40.7%. After adjustments, the presence of the IL13 rs20541A- allele (OR 3.06, 95% CI 1.42-6.58, p = 0.004) or multisensitization (adjusted OR 4.59, 95% CI 1.48-14.26, p = 0.008) was associated with AR/AC asthma. Nasal polyps and acetylsalicylic acid-exacerbated respiratory disease was also associated with AR/AC asthma.

CONCLUSIONS

Adult AR/AC asthma could putatively be a phenotype, characterized by the presence of atopic and/or eosinophilic factors and a high prevalence of the IL13 rs20541A- allele. Studies on the mechanisms behind this and in other populations are needed.

Prevalence of allergic sensitization to conifer pollen in a high cypress exposure area

Background:

Sensitization to Pinales (Cupressaceae and Pinaceae) has increased dramatically in recent years. The prevalence of sensitization in different geographic areas is related to exposure to specific pollens.

Objectives:

To investigate the prevalence of allergy to different conifer pollens, describe the characteristics of patients with such allergy, and identify the involved allergens.

Methods:

Patients were recruited at five hospitals near Madrid. Extracts from conifer pollen were prepared and used in skin-prick testing. Wheal sizes were recorded, and serum samples obtained from patients with positive reactions to Cupressus arizonica and/or Pinus pinea. The specific immunoglobulin E value to C. arizonica and Cup a 1 was determined. Individual immunoblots for each patient and with a pool of sera were performed. Allergenic proteins were sequenced by using liquid chromatography-tandem mass spectrometry.

Results:

Of 499 individuals included in the study, 17 (14%) had positive skin-prick test results to some conifer pollen extracts. Sixty-four patients had positive results to C. arizonica (prevalence 12.8%) and 11 had positive results to P. pinea (2.2%). All the patients had respiratory symptoms (61.4% during the C. arizonica pollination period), and 62.9% had asthma. Approximately 86% of the patients had positive specific immunoglobulin E results to C. arizonica and 92.3% had positive results to Cup a 1. Fourteen different bands were recognized by immunoblot; the most frequent bands were those detected at 43, 18, 16, and 14 kDa. All sequenced proteins corresponded to Cup a 1.

Conclusion:

Allergy to conifer pollen could be considered a relevant cause of respiratory allergy in central Spain. Asthma was more frequent than in other studies. We only identified Cup a 1 as involved in sensitization.

Asthma prevalence and risk factors in early childhood at Northern Portugal

Asthma is the commonest and most important chronic non-infectious disease in childhood and it has become more prevalent in recent years. There is a shortage of studies in relation to early childhood and so, as part of the INAIRCHILD project, this cross-sectional study aimed to assess the prevalence of asthma and its associated risk factors, namely demographic, environmental, psychosocial and clinical factors for infants and preschoolers living in Northern Portugal. Data concerning asthma prevalence were collected through questionnaires based on those from the International Study of Asthma and Allergies in Childhood (ISAAC-derived), the questionnaires were distributed to 1042 children attending the 17 nurseries involved in the INAIRCHILD project (10 in urban and suburban context, and 7 in rural context). The response rate was 48%. Prevalence of asthma based on symptomatology and odds ratio was calculated. Around 52% of the studied children presented at least one of the respiratory symptoms investigated (wheeze, dyspnea and cough) in the absence of upper respiratory infections. The prevalence of asthma was 10.7%, comparable to the figures for Portuguese schoolchildren (6-7 years old) reported by the national Directorate-General of Health, thus showing that an early diagnosis might be possible and helpful for the mitigation of childhood asthma. Environmental context (urban, suburban or rural), gender and family asthma history showed clear associations with asthma prevalence, namely non-rural location, male gender, and having an asthmatic parent were found to be risk factors.

Prevalence and risk factors of COPD among never-smokers in two areas of Sweden - Occupational exposure to gas, dust or fumes is an important risk factor

BACKGROUND

Although active tobacco smoking is the main risk factor for COPD, COPD is not uncommon also among never-smokers. Different study locations along with different spirometric definitions of COPD have historically yielded different prevalence estimates of the disease.

AIM

To study current prevalence and risk factors of COPD among never-smokers in two areas of Sweden.

METHODS

Data collected in 2008-2012 within the West Sweden Asthma Study and Obstructive Lung Disease in Northern Sweden Studies was pooled. The study population consisted of 1839 subjects who participated in spirometry and interviews. COPD was defined as post-bronchodilator a) FEV(1)/(F)VC < 0.7, b) FEV(1)/FVC < 0.7 and c) FEV(1)/FVC < lower limit of normal.

RESULTS

Of the 1839 subjects, 967 (52.6%) were never-smokers. Among the never-smoking subjects, the prevalence of COPD according to definitions a-c was 7.7%, 4.9% and 3.0%, respectively. The corresponding prevalence of GOLD grade ≥2 was 2.0%, 1.4% and 1.3%. No significant difference in prevalence between the two study areas was observed. In never-smokers, occupational exposure to gas, dust or fumes (GDF) was significantly associated with both COPD (OR 1.85, 95% CI 1.03-3.33), and GOLD ≥2 (OR 4.51, 1.72-11.9) according to definition a), after adjusting for age, educational level and exposure to passive smoking at work.

CONCLUSION

Depending on definition, prevalence of COPD among never-smokers was 3.0-7.7%, whereas GOLD ≥2 was present in 1.3-2.0%. Occupational exposure to GDF remained independently and significantly associated with COPD regardless of spirometric definition of the disease.

Sensitization pattern affects the asthma risk in Finnish adult population

BACKGROUND

There is a large global variation in the sensitization pattern and its association with allergic diseases. In temperate and tropical urban environments, mite monosensitization can be the predominant cause of allergic airway diseases, whereas in other environments, polysensitization is more typical. Sensitization to mite allergens associates with asthma. However, it is suggested that mite sensitization might play a minor role in Northern Europe. The aim of the study was to analyze how sensitization pattern affects the asthma risk in Finnish adults, with a special focus on mites.

METHODS

A population-based case-control data (N = 523) from Finnish adult asthma patients with one or two matched controls were used. Asthma was diagnosed based on a typical history of asthmatic symptoms and lung function tests. The allergic sensitization was determined based on skin prick test (SPT) of five mites, three molds, and nine other aeroallergens. Information on demographics was obtained by a questionnaire.

RESULTS

The proportion of sensitization to any allergen was 55% in the asthma group and 39% in the control group (P = 0.001, OR 2.06, 95% CI = 1.35-3.14). Sensitization to animal dander, pollen, or Aspergillus fumigatus was associated with asthma. Polysensitization to more than one allergen types and the number of SPT-positive reactions associated with asthma, whereas sensitization to only one allergen type was not associated with asthma.

CONCLUSIONS

The large number of sensitizations to several types of allergens distinguishes subjects with asthma. Mite sensitization had little independent association with asthma in Finland.

A persistently high body mass index increases the risk of atopic asthma at school age

Aim

Being overweight has been associated with the risk of developing childhood asthma, but studies have produced conflicting results, for example with regard to possible links to allergic diseases. This study aimed to explore the relationship between body mass index (BMI) and school-age asthma.

Methods

Data were obtained from a prospective, longitudinal study of 5044 children born in western Sweden. The parents answered questionnaires at six months and one, four-and-a-half and eight years of age. The response rate to the final questionnaire at the age of eight was just over 80%. BMI was adjusted for age and gender, and a high BMI was defined as the 85th percentile and above.

Results

A multivariate analysis showed an independently increased risk of doctor-diagnosed asthma among children with a persistently high BMI, both in infancy and at school age, with an adjusted odds ratio (aOR) of 2.9 and a 95% confidence interval (CI) of 1.3–6.4. In addition, persistently high BMI was associated with an increased risk of atopic asthma (aOR 4.7, 95% CI 2.0–11.0).

Conclusion

A persistently high BMI during childhood increased the risk of doctor-diagnosed asthma at school age. The increased risk of atopic asthma suggests an effect mediated via the immune system.