Elsy Jönsson

Different pattern of risk factors for atopic and nonatopic asthma among children – report from the Obstructive Lung Disease in Northern Sweden Study

Background: A cross‐sectional study was performed among 7–8‐year‐old schoolchildren during the winter of 1996 in three municipalities in the most northern province of Sweden, Norrbotten. The study was the starting point of a longitudinal study of asthma, rhinitis, eczema, and type‐1 allergy, and provided data on prevalence and risk factors for these conditions. The aim of the present study was to validate the classification of asthma based on a parental questionnaire, and to examine risk factors for atopic and nonatopic asthma.

Asthma, type-1 allergy and related conditions in 7- and 8-year-old children in Northern Sweden: prevalence rates and risk factor pattern

As a first step in an intervention study of asthma and allergic diseases among school children, a cross-sectional study was performed during Winter 1996 in three towns (Kiruna, Luleå and Piteå) in the northernmost province of Sweden, Norrbotten. The cross-sectional study aimed to measure the prevalence of asthma, type-1 allergy and allergic diseases in order to make it possible to measure the incidence of the diseases, conditions and symptoms related to the diseases. Another aim was to perform a screening for possible risk factors. All children enrolled in the first and second classes at school, 7 and 8 years old, were invited to take part in this study. The ISAAC questionnaire with added questions about symptoms, morbidity, heredity and environment was distributed by the schools to the parents. The response rate was 97%, and 3431 completed questionnaires were returned. The children in two of the municipalities were also invited to skin test, and 2149 (88%) were tested with 10 common airborne allergens. The results showed that 7% of the children were currently using or had used asthma medicines during the last 12 months. Six percent had asthma diagnosed by a physician, and 4% were using inhaled corticosteroids. The prevalence of wheezing during the last 12 months was 12%, rhinitis without colds 14%, and eczema 27%, while 21% had a positive skin test. The respiratory symptoms and conditions were significantly greater in boys and, further, they were most prevalent in Kiruna in the very north, though not significantly. Type-1 allergy and asthma had different risk factor patterns. The main risk factors for asthma were a family history of asthma (OR = 3.2) followed by past or present house dampness (OR = 1.9), male sex (OR = 1.7) and a smoking mother (OR = 1.6). In Kiruna, when none of these three risk factors were present, none of the children had asthma, but when all three were present, 38% of these children were using asthma medicines.

Does non-responder bias have a significant effect on the results in a postal questionnaire study?

Background and aim: In epidemiological questionnaire studies results can be influenced by non-responder bias. However, in respiratory epidemiology this has been analysed in very few recently published papers. The aim of our paper is to assess if the results found in our previous postal questionnaire study in an adult population in Northern Finland were biased by non-response. Methods: A random sample of 385 persons from the 1284 non-responders in a previous postal questionnaire study was examined. The same questionnaire as in the original study was again mailed to these persons, and those still not answering were contacted by phone. Results: Totally 183 complete answers (48%) were collected. Lack of interest (56%) and forgetting to mail the response letter (22%) were the most common reasons to non-response. Typical non-responders were young men and current smokers who less frequently reported respiratory symptoms in exercise and asthma than the responders in the original study. Answers collected by phone gave for some questions higher prevalence rates than postal answers. Conclusion: Firstly, in this population the response rate (83.6%) in the original study was high enough to provide reliable results for respiratory symptoms and diseases, only the prevalence of current smoking was biased by non-response. Secondly, the methods used for collecting responses in a non-response study may influence the results.

Smoking, Respiratory Symptoms, and Diseases: A Comparative Study Between Northern Sweden and Northern Finland: Report From the FinEsS Study

STUDY OBJECTIVES The influences of different smoking categories on the prevalence of respiratory symptoms, asthma, and chronic bronchitis have been examined in the most northern province of Sweden, Norrbotten, and in Lapland, Finland. The two areas have similar geographic and demographic conditions. METHODS AND STUDY POPULATION The study is a part of the FinEsS studies, which are epidemiologic respiratory surveys in progress in Sweden, Finland, and Estonia. A random sample of 20- to 69-years-olds were invited to answer a postal questionnaire about respiratory symptoms, smoking habits, and occupation. In Norrbotten, 8,333 subjects were invited and 7,104 responded (85%). In Lapland, 8,005 were invited and 6,633 responded (83%). RESULTS The participation by age and sex was similar in both countries. The prevalence of smokers in Lapland was 32% vs 26% in Norrbotten. Significantly more women than men in Norrbotten were smokers, while the opposite was true for Lapland. Sputum production was the most prevalent symptom in both areas, 25% in Lapland vs 19% in Norrbotten. The prevalence of chronic productive cough was 11% in Lapland and 7% in Norrbotten. Bronchitic symptoms were more prevalent in Lapland among both smokers and nonsmokers. A positive family history of chronic obstructive airway disease together with increased number of consumed cigarettes showed an additive effect for both chronic productive cough and wheezing. The odds ratio (OR) for wheezing during the last 12 months was 3.8 for subjects without a family history of obstructive airway disease who consumed > 14 cigarettes per day compared with nonsmokers, but if the subjects had a family history of obstructive airway disease, the risk for wheezing increased to OR 8.4. CONCLUSION Bronchitic symptoms were more common in Finland. The difference remained also after correction for demographic variables including smoking habits, age and socioeconomic group, and family history of obstructive airway disease. Identical methods, sample composition, and the high participation rate contribute to the validity of the results. Air pollution, including environmental tobacco smoke, may contribute to the difference. To explain the difference, further analysis and investigations of social and environmental factors as well as genetic factors are needed.

Increasing prevalence of asthma but not of chronic bronchitis in Finland? Report from the FinEsS-Helsinki study

To assess the prevalence of asthma, chronic bronchitis and respiratory symptoms, and to calculate risk factors for them, we performed a postal survey in Helsinki, the capital of Finland. During the spring of 1996, questionnaires were mailed to a random sample of 8000 individuals aged 20-69. The total response rate was 76%, with 6062 complete answers. The prevalence of having ever had asthma was 7.2%, physician-diagnosed asthma was 6.6% and physician-diagnosed chronic bronchitis was 3.7%. Asthma was significantly more common among women than men, but no gender differences existed in prevalence of chronic bronchitis. The most common respiratory symptom was sputum production when coughing, reported by 27%. During the previous 12 months, wheezing had occurred in 20% and attacks of shortness of breath in 13% of subjects. Generally, the prevalence of different respiratory symptoms were significantly higher among smokers. The most important risk factor for asthma was a family history of asthma (Odds ratio:OR 3.3). Multivariate analysis revealed that being a member of the socioeconomic group, manual workers, was associated with a significantly increased risk for chronic productive cough (OR 1.7), and for wheezing during the previous 12 months (OR 1.7). Manual workers of both genders had the highest prevalence of asthma, chronic productive cough and wheezing during the previous 12 months. The prevalence of asthma in Helsinki was higher than previously found in Finland, and was at a similar level to that of other Nordic countries. In contrast, prevalence of chronic bronchitis was lower than previously shown in Finland.

Remission of asthma in the middle aged and elderly: report from the Obstructive Lung Disease in Northern Sweden study

BACKGROUND Remission of asthma in adults has been considered to be low but is still not well documented. In children remission occurs with a rate estimated at approximately 50%. Remission of asthma in middle aged and elderly subjects was investigated as part of a population based study of respiratory diseases in Northern Sweden. METHODS In 1986 86% of 6610 subjects participated in a questionnaire survey. After a clinical validation study 300 subjects were diagnosed as having current asthma. In 1996 5935 subjects of the cohort could be traced for a third survey and 87% participated. Of the subjects with current asthma in 1986, 267 participated. In addition, 60 symptomatic subjects were classified as suspected asthma and 58 of them participated in 1996. Remission of asthma was defined as no recurrent wheeze, no attacks of shortness of breath, and no use of asthma medicines in 1996. RESULTS Remission of asthma during the 10 year period under study was 6%. In subjects with suspected asthma, remission occurred in 22%. The average annual remission rate was less than 1%. Remission was associated with previously mild disease and cessation of smoking. CONCLUSION Remission of asthma or the disappearance of its symptoms to an asymptomatic latent phase appeared to be rare in middle aged and elderly subjects.

Clinical InvestigationsSmoking, Respiratory Symptoms, and Diseases: A Comparative Study Between Northern Sweden and Northern Finland: Report From the FinEsS Study

STUDY OBJECTIVES The influences of different smoking categories on the prevalence of respiratory symptoms, asthma, and chronic bronchitis have been examined in the most northern province of Sweden, Norrbotten, and in Lapland, Finland. The two areas have similar geographic and demographic conditions. METHODS AND STUDY POPULATION The study is a part of the FinEsS studies, which are epidemiologic respiratory surveys in progress in Sweden, Finland, and Estonia. A random sample of 20- to 69-years-olds were invited to answer a postal questionnaire about respiratory symptoms, smoking habits, and occupation. In Norrbotten, 8,333 subjects were invited and 7,104 responded (85%). In Lapland, 8,005 were invited and 6,633 responded (83%). RESULTS The participation by age and sex was similar in both countries. The prevalence of smokers in Lapland was 32% vs 26% in Norrbotten. Significantly more women than men in Norrbotten were smokers, while the opposite was true for Lapland. Sputum production was the most prevalent symptom in both areas, 25% in Lapland vs 19% in Norrbotten. The prevalence of chronic productive cough was 11% in Lapland and 7% in Norrbotten. Bronchitic symptoms were more prevalent in Lapland among both smokers and nonsmokers. A positive family history of chronic obstructive airway disease together with increased number of consumed cigarettes showed an additive effect for both chronic productive cough and wheezing. The odds ratio (OR) for wheezing during the last 12 months was 3.8 for subjects without a family history of obstructive airway disease who consumed > 14 cigarettes per day compared with nonsmokers, but if the subjects had a family history of obstructive airway disease, the risk for wheezing increased to OR 8.4. CONCLUSION Bronchitic symptoms were more common in Finland. The difference remained also after correction for demographic variables including smoking habits, age and socioeconomic group, and family history of obstructive airway disease. Identical methods, sample composition, and the high participation rate contribute to the validity of the results. Air pollution, including environmental tobacco smoke, may contribute to the difference. To explain the difference, further analysis and investigations of social and environmental factors as well as genetic factors are needed.

Are symptoms of obstructive sleep apnoea syndrome related to bronchitic symptoms or lung function impairment? Report from the Obstructive Lung Disease in Northern Sweden Study

To investigate whether the high prevalence of symptoms related to obstructive sleep apnoea syndrome (OSAS) in a bronchitic cohort is correlated with the bronchitic symptoms or lung function impairment we examined two cohorts with bronchitic symptoms (n = 357 and 82) and a reference group who had reported no respiratory symptoms in a previous survey in 1986 (n = 140). The study was a part of the Obstructive Lung Disease in Northern Sweden Study and included clinical examination and lung function tests. Although lung function measured as FEV1 percentage predicted was correlated with bronchitic symptoms we found that bronchitic symptoms and body mass index but not lung function impairment were correlated with symptoms related to obstructive sleep apnoea. According to our findings it was the various bronchitic symptoms such as longstanding cough, wheezing, sputum production and chronic productive cough that were correlated with OSAS symptoms. This might be due to increased upper airway swelling or increased upper airway resistance, and lung function impairment does not seem to be responsible for the high prevalence of symptoms related to obstructive sleep apnoea in this bronchitic cohort.