Linda Ekerljung

West Sweden Asthma Study: Prevalence trends over the last 18 years argues no recent increase in asthma

Asthma prevalence has increased over the last fifty years, but the more recent changes have not been conclusively determined. Studies in children indicate that a plateau in the prevalence of asthma may have been reached, but this has not yet been confirmed in adults. Epidemiological studies have suggested that the prevalence of asthma in adults is approximately 7-10% in different parts of the western world.We have now performed a large-scale epidemiological evaluation of the prevalence of asthma and respiratory symptoms in adults between the ages of 16-75 in West Sweden. Thirty thousand randomly chosen individuals were sent a detailed questionnaire focusing on asthma and respiratory symptoms, as well possible risk factors. Sixty-two percent of the contacted individuals responded to the questionnaire. Asthma prevalence, defined as asthma diagnosed by a physician, was 8.3%. Moreover, the prevalence of respiratory symptoms was lower compared to previous studies. The most common respiratory symptom was any wheeze (16.6%) followed by sputum production (13.3%). In comparison with studies performed 18 years ago, the prevalence of asthma has not increased, and the prevalence of most respiratory symptoms has decreased. Therefore, our data argues that the continued increase in asthma prevalence that has been observed over the last half century is over.

Large scale questionnaire survey on respiratory health in Sweden: effects of late- and non-response.

BACKGROUND Participation rates in epidemiologic studies conducted with postal questionnaires have steadily declined since 1970s. This can lead to an increased risk for selection bias. The aim of this study was to examine cause and effect of non-response in a large cross sectional study assessing respiratory health in western Sweden. METHODS The study sample was 29,218. The response rate to the initial postal questionnaire was 33%. The response rates to subsequent postal reminders were 15%, 7% and 7% of eligible participants totalling a participation of 62%. Of those who did not respond to the postal survey, a random sample of 400 subjects were identified and contacted for interview by telephone. RESULTS Non-responders did not differ significantly in prevalence of airway diseases or symptoms when compared with responders. Male sex, young age and smokers were underestimated among non-responders. No clear trends in prevalence of respiratory symptoms and report of asthma were found with delayed response to the postal survey. The proportion of smokers and men increased with increasing number of reminders. Letters reminding subjects about the study did increase the participation rate but did not alter the risk estimates. CONCLUSION We conclude that with a response rate of 62%, our estimate of disease and symptom prevalence was not biased in this Swedish population. However, smoking was underestimated. No general trend for late-responders was seen and therefore we conclude that extrapolation of results to non-responders is not possible in our study. Causes of non-response were mainly due to circumstantial factors.

Increased Prevalence of Symptoms of Rhinitis but Not of Asthma between 1990 and 2008 in Swedish Adults: Comparisons of the ECRHS and GA2LEN Surveys

Background The increase in asthma prevalence until 1990 has been well described. Thereafter, time trends are poorly known, due to the low number of high quality studies. The preferred method for studying time trends in prevalence is repeated surveys of similar populations. This study aimed to compare the prevalence of asthma symptoms and their major determinants, rhinitis and smoking, in Swedish young adults in 1990 and 2008. Methods In 1990 the European Community Respiratory Health Survey (ECRHS) studied respiratory symptoms, asthma, rhinitis and smoking in a population-based sample (86% participation) in Sweden. In 2008 the same symptom questions were included in the Global Allergy and Asthma European Network (GA2LEN) survey (60% participation). Smoking questions were however differently worded. The regions (Gothenburg, Uppsala, Umeå) and age interval (20–44 years) surveyed both in 1990 (n = 8,982) and 2008 (n = 9,156) were analysed. Results The prevalence of any wheeze last 12 months decreased from 20% to 16% (p<0.001), and the prevalence of “asthma-related symptoms” was unchanged at 7%. However, either having asthma attacks or using asthma medications increased from 6% to 8% (p<0.001), and their major risk factor, rhinitis, increased from 22% to 31%. Past and present smoking decreased. Conclusion From 1990 to 2008 the prevalence of obstructive airway symptoms common in asthma did not increase in Swedish young adults. This supports the few available international findings suggesting the previous upward trend in asthma has recently reached a plateau. The fact that wheeze did not increase despite the significant increment in rhinitis, may at least in part be due to the decrease in smoking.

Growing up on a farm leads to lifelong protection against allergic rhinitis.

To cite this article: Eriksson J, Ekerljung L, Lötvall J, Pullerits T, Wennergren G, Rönmark E, Torén K, Lundbäck B. Growing up on a farm leads to lifelong protection against allergic rhinitis. Allergy 2010; 65: 1397–1403.

No further increase of incidence of asthma: Incidence, remission and relapse of adult asthma in Sweden

BACKGROUND Knowledge about time trends of disease patterns in society is essential for planning and prioritizing health care resources. Longitudinal population-based studies on asthma are scarce but provide an opportunity to assess incidence, remission and relapse of asthma, and their determinants, which were the objectives of the present study. METHODS A postal questionnaire was sent on two occasions, 1996 and 2006, to a randomly selected sample of subjects aged 20-69 years in 1996. The response rates were 72% and 83%, respectively, and in total 4479 subjects participated in both surveys. The questionnaire included questions on asthma, respiratory symptoms and possible determinants. Logistic regression was used to assess determinants. RESULTS Cumulative incidence of asthma was 2.4% (men 1.9%; women 2.8%, p=0.06). Family histories of asthma (OR 2.31, CI 95% 1.42-3.76), rhinitis (OR 2.25, CI 95% 1.43-3.53) and being an ex-smoker (OR 2.17, CI 95% 1.27-3.71) were determinants for incident asthma. The 10-year remission of asthma was 14.6% and inversely associated with rhinitis. Relapse was found in 38% of eligible subjects. CONCLUSIONS The current study with high participation rates concludes that the incidence of asthma among adults has been stable in Sweden for the past two decades. Remission was associated with mild disease at study start. Relapse in adults has rarely been reported previously and provide new insight in the course of asthma. Low remission and high relapse further support the view of asthma as a chronic disease; possibly representing fluctuations of the disease over time.

Passive Smoking Exposure Is Associated With Increased Risk of COPD in Never Smokers

BACKGROUND Passive smoking, or environmental tobacco smoke (ETS), is a risk factor for lung cancer, cardiovascular disease, and childhood asthma, but a relationship with COPD has not been fully established. Our aim was to study ETS as a risk factor for COPD in never smokers. METHODS Data from three cross-sectional studies within the Obstructive Lung Disease in Northern Sweden (OLIN) database were pooled. Of the 2,182 lifelong never smokers, 2,118 completed structured interviews and spirometry of acceptable quality. COPD was defined according to the GOLD (Global Initiative for Chronic Obstructive Lung Disease) criteria using postbronchodilator spirometry. The association of COPD with ETS in single and multiple settings was calculated by multivariate logistic regression adjusting for known risk factors for COPD. RESULTS COPD prevalence was associated with increased ETS exposure: 4.2% (no ETS), 8.0% (ETS ever at home), 8.3% (ETS at previous work), and 14.7% (ETS ever at home and at both previous and current work), test for trend P = .003. Exclusion of subjects aged ≥ 65 years and subjects reporting asthma yielded similar results. ETS in multiple settings, such as ever at home and at both previous and current work, was strongly associated to COPD (OR, 3.80; 95% CI, 1.29-11.2). CONCLUSIONS In this population-based sample of never smokers, ETS was independently associated with COPD. The association was stronger for ETS in multiple settings. ETS in multiple settings was, after age, the strongest risk factor for COPD and comparable to personal smoking of up to 14 cigarettes/d in comparable materials. The findings strongly advocate measures against smoking in public places.

RNA-containing exosomes in human nasal secretions.

Background Exosomes are nanovesicles of endocytic origin released by cells and present in human body fluids such as plasma, breast milk, and bronchoalveolar lavage fluid. These vesicles take part in communication between cells. Recently, it was shown that exosomes contain both mRNA and microRNA. This RNA can be shuttled between cells (exosomal shuttle RNA), which is a new route of communication between cells. The aim of this study was to determine whether nasal secretions harbor exosomes and furthermore, whether these exosomes contain RNA. Methods Human nasal lavage fluid (NLF) underwent centrifugation and filtration to discard cells and debris, followed by a final ultracentrifugation at 120,000 × g to pellet the exosomes. Exosomes were detected using electron microscopy (EM), flow cytometry, and Western blot. RNA was extracted and analyzed using a Bioanalyzer. Results Exosomes were visualized as 40–80 nm, CD63+ vesicles using EM. Flow cytometry of exosomes using anti–major histocompatibility complex class II beads revealed exosomes positive for the tetraspanins CD9, CD63, and CD81. Western blot confirmed the presence of exosomal protein and absence of proteins from the endoplasmic reticulum (ER), because the exosomes were positive for Tsg101, but negative for the ER marker, calnexin. Bioanalyzer analysis revealed that, these exosomes contain RNA. Conclusion This study shows for the first time that NLF contains exosomes and that these exosomes contain RNA. Further characterization of the exosomal RNA and proteins may provide important information about communication in the nose and potentially provide a source of biomarkers for upper airway diseases.

Eczema among adults: prevalence, risk factors and relation to airway diseases. Results from a large-scale population survey in Sweden.

Background  In contrast to asthma and rhinitis, few studies among adults investigating the prevalence and risk factors of eczema have been published.

Multi-symptom asthma is closely related to nasal blockage, rhinorrhea and symptoms of chronic rhinosinusitis-evidence from the West Sweden Asthma Study

BackgroundWe have previously shown that approximately 25% of those with asthma in West Sweden have multiple asthma symptoms, which may describe a group of patients with more severe disease. Furthermore, asthma is associated with several co-morbid diseases, including rhinitis and chronic rhinosinusitis. The aim of this study was to determine whether multi-symptom asthma is related to signs of severe asthma, and to investigate the association between multi-symptom asthma and different symptoms of allergic and chronic rhinosinusitis.MethodsThis study analyzed data on asthma symptoms, rhinitis, and chronic rhinosinusitis from the 2008 West Sweden Asthma Study, which is an epidemiologically based study using the OLIN and GA2LEN respiratory and allergy focused questionnaires.ResultsMulti-symptom asthma was present in 2.1% of the general population. Subjects with multi-symptom asthma had more than double the risk of having night-time awakenings caused by asthma compared with those with fewer asthma symptoms (P < 0.001). The prevalence of allergic rhinitis was similar in the fewer- and multi-symptom asthma groups, but nasal blockage and rhinorrhea were significantly increased in those with multi- versus fewer-symptom asthma (odds ratio 2.21; 95% confidence interval 1.64-2.97, versus 1.49; 1.10-2.02, respectively). Having any, or one to four symptoms of chronic rhinosinusitis significantly increased the risk of having multi- versus fewer-symptom asthma (P < 0.01).ConclusionAn epidemiologically identified group of individuals with multiple asthma symptoms harbour to greater extent those with signs of severe asthma. The degree of rhinitis, described by the presence of symptoms of nasal blockage or rhinorrhea, as well as the presence of any or several signs of chronic rhinosinusitis, significantly increases the risk of having multi-symptom asthma.

Asthma in late adolescence – farm childhood is protective and the prevalence increase has levelled off

Wennergren G, Ekerljung L, Alm B, Eriksson J, Lötvall J, Lundbäck B. Asthma in late adolescence – farm childhood is protective and the prevalence increase has levelled off.
Pediatr Allergy Immunol 2010: 21: 806–813.
© 2010 John Wiley & Sons A/S