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Objective: To investigate the current prevalence of physician-diagnosed obstructive airway diseases by respiratory symptoms and by sex in Sweden and Finland., Method: In 2016, a postal questionnaire was answered by 34,072 randomly selected adults in four study areas: Västra Götaland and Norrbotten in Sweden, and Seinäjoki-Vaasa and Helsinki in Finland., Results: The prevalence of asthma symptoms was higher in Norrbotten (13.2%), Seinäjoki-Vaasa (14.8%) and Helsinki (14.4%) than in Västra Götaland (10.7%), and physician-diagnosed asthma was highest in Norrbotten (13.0%) and least in Västra Götaland (10.1%). Chronic productive cough was most common in the Finnish areas (7.7-8.2% versus 6.3-6.7%) while the prevalence of physician-diagnosed chronic bronchitis (CB) or chronic obstructive pulmonary disease (COPD) varied between 1.7 and 2.7% in the four areas. Among individuals with respiratory symptoms, the prevalence of asthma was most common in Norrbotten, while a diagnosis of COPD or CB was most common in Västra Götaland and Seinäjoki-Vaasa. More women than men with respiratory symptoms reported a diagnosis of asthma in Sweden and Seinäjoki-Vaasa but there were no sex differences in Helsinki. In Sweden, more women than men with symptoms of cough or phlegm reported a diagnosis of CB or COPD, while in Finland the opposite was found., Conclusion: The prevalence of respiratory symptoms and corresponding diagnoses varied between and within the countries. The proportion reporting a diagnosis of obstructive airway disease among individuals with respiratory symptoms varied, indicating differences in diagnostic patterns both between areas and by sex.

Background: Child-onset asthma is known to remit with high probability, but remission in adult-onset asthma is seemingly less frequent. Reports of the association between remission and asthma age of onset up to late adulthood are scarce., Objective: To evaluate the association between asthma remission, age at diagnosis and gender, and assess risk factors of nonremission., Methods: In 2016, a random sample of 16,000 subjects aged 20 to 69 years from Helsinki and Western Finland were sent a FinEsS questionnaire. Physician-diagnosed asthma was categorized by age at diagnosis to early- (0-11 years), intermediate- (12-39 years), and late-diagnosed (40-69 years) asthma. Asthma remission was defined by not having had asthma symptoms and not having used asthma medication in the past 12 months., Results: Totally, 8199 (51.5%) responded, and 879 reported physician-diagnosed asthma. Remission was most common in early-diagnosed (30.2%), followed by intermediate-diagnosed (17.9%), and least common in late-diagnosed asthma (5.0%) (P < .001), and the median times from diagnosis were 27, 18.5, and 10 years, respectively. In males, the corresponding remission rates were 36.7%, 20.0%, and 3.4%, and in females, 20.4%, 16.6%, and 5.9% (gender difference P < .001). In multivariable binary logistic regression analysis, significant risk factors of asthma nonremission were intermediate (odds ratio [OR] = 2.15, 95% confidence interval: 1.37-3.36) and late diagnosis (OR = 11.06, 4.82-25.37) compared with early diagnosis, chronic obstructive pulmonary disease (COPD) (OR = 5.56, 1.26-24.49), allergic rhinitis (OR = 2.28, 1.50-3.46), and family history of asthma (OR = 1.86, 1.22-2.85). Results were similar after excluding COPD., Conclusion: Remission was rare in adults diagnosed with asthma after age 40 years in both genders. Late-diagnosed asthma was the most significant independent risk factor for nonremission., (Copyright © 2020 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Background: Mortality and hospitalization due to asthma have decreased in many European countries, but asthma symptoms still cause a lot of morbidity and costs., Objectives: We evaluated prevalence trends of asthma, asthma symptoms and allergic rhinoconjunctivitis in adults aged 20-69 years during a 20-year period from 1996 to 2016 in the city of Helsinki, the capital of Finland., Methods: Three cross-sectional postal surveys were conducted in random population samples 10 years apart. In 1996, 2006 and 2016, a total of 6062 (response rate 75.9%), 2449 (61.9%) and 4026 subjects (50.3%) took part, respectively., Results: In all responders, the prevalence of physician-diagnosed asthma was 6.6% in 1996, 10% in 2006 and 10.9% in 2016. The prevalence increased from 1996 to 2006, but stabilized from 2006 to 2016, both in men and women and in smokers and non-smokers. The prevalence of current asthma (8.5% in 2006 and 8.8% in 2016) and of asthma with rhinoconjunctivitis (7.6% in 2006 and 7.5% in 2016) remained also at the same level. Allergic rhinoconjunctivitis decreased significantly from 2006 (42.7%) to 2016 (39.0%, p = 0.004). Those with physician diagnosed asthma reported significantly less symptoms in 2016 compared to 2006 and 1996, although there was no change in smoking habits or medication use. Young asthmatics (20-29 years) without rhinoconjunctivitis reported least symptoms., Conclusion: Previously observed increase of physician-diagnosed asthma prevalence in adults seems to be levelling off in Helsinki, and patients have fewer symptoms than 20 years ago. In addition, allergic rhinoconjunctivitis is less frequent than 10 years earlier. (247 words)., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

To assess risk factors related to the development of chronic obstructive pulmonary disease (COPD) including smoking and occupational exposure (OE) to dusts, gases or fumes, we performed a longitudinal 11-year follow-up postal survey. The original study population was a random population sample of 8000 inhabitants of Helsinki aged 20 to 69 years in 1996. Participants of the first postal questionnaire were invited to this follow-up survey in 2007 with 4302 (78%) answers obtained. Cumulative incidence of COPD in 11 years was 3.43% corresponding to an incidence rate of 3.17/1000/year after exclusion of those with self-reported physician-diagnosed COPD and ever COPD in 1996. Smoking and age, but not gender, were associated with incident COPD. Reported family history of COPD increased the cumulative incidence to 8.55% vs 3.04% among those without a family history (p < 0.001). In multivariate analysis, significant independent risk factors for incident COPD were: current smoking in 1996 (OR 4.40 [95% CI 2.89-6.71]), age over 50 (OR 3.42 [95% CI 2.22-5.26]), family history of COPD (OR 2.08 [1.27-3.43]), ever asthma (OR 2.28 [1.35-3.86]), and self-reported OE (OR 2.14 [1.50-3.05]). Occupational exposure to dusts, gases or fumes, assessed both based on self-reported exposure and a job exposure matrix using reported professions, was an independent risk factor for incident COPD. Smoking and OE together yielded an additive effect on incidence of COPD.

Our aim was to study the association of smoking habits and environmental tobacco smoke (ETS) exposure with bronchial hyperresponsiveness (BHR). A random sample of 292 adults was examined using a structured interview, spirometry, skin prick tests, exhaled nitric oxide fraction (FeNO) and bronchial histamine challenge. A large majority of subjects with BHR were smokers or ex-smokers. Starting to smoke before 20 years of age was significantly associated with BHR, as was current smoking, quantity of smoking and ETS exposure. The severity of BHR increased significantly with increasing pack-years of exposure (p<0.001). Current smokers with decreased lung function were at a particularly high risk of BHR. Impaired forced expiratory volume in 1 s and mean maximal expiratory flow were independent determinants for more severe BHR, regardless of age. In multivariate analysis, smoking remained an independent determinant for BHR after adjustment for impaired lung function and other covariates: ≥15 pack-years yielded an odds ratio of 3.00 (95% CI 1.33-6.76) for BHR. The association between BHR and FeNO was dependent on smoking habits. The results indicate that smoking is a significant risk factor for BHR, with a dose-dependent pattern, and that the severity of BHR increases with pack-years. The findings strongly suggest assessment of smoking habits in subjects with BHR.

Objectives: To evaluate current occupational exposure and its associations with asthma control, exacerbations, and severity in middle-aged men with asthma from youth., Methods: We used the Finnish Defence Force registers, 1986 to 1990, to select conscripts with asthma to represent mild or moderate asthmatic group (asthma group 1; N = 505), men who were exempted from military service to represent relatively severe asthmatic group (asthma group 2; N = 393), and a control group without asthma (N = 1500). A questionnaire was sent out in 2009., Results: The current self-reported or expert-evaluated exposure to asthma-aggravating factors differed only slightly between the asthmatic groups and the controls. In asthma group 2, being a manual worker or self-employed (odds ratio, 4.5; 95% confidence interval, 1.2 to 16.3) significantly associated with asthma exacerbations., Conclusions: Current work may associate with the asthma outcome of middle-aged men with relatively severe asthma in their youth.

Purpose: To assess the predictive value of lung function impairment on mortality among asbestos-exposed workers., Methods: A total of 590 workers originally screened for occupational lung disease including spirometry and pulmonary diffusing capacity measurements were followed up for mortality data (ICD-10 classification). The mean follow-up time was 10.5 years. Associations of different lung function parameters with mortality from all causes and from cardiovascular (I00-I99) and non-malignant respiratory diseases (J00-J99) were analysed. Factor analysis was used to create obstructive and restrictive factors., Results: A total of 191 deaths were found altogether. Most measured lung function variables were associated with increased mortality when studied separately. Both decreased forced expiratory flow in one second (hazard ratio/measurement unit = 0.977, 95 % CI 0.969-0.988, p < 0.001) and impaired diffusing capacity (0.973, 0.965-0.981, p < 0.001) were independently associated with mortality from all causes, as well as from cardiovascular and non-malignant respiratory diseases. Both obstructive factor alone and the sum of obstructive and restrictive factors were associated with all studied mortality categories. The restrictive factor alone was associated with all-cause and respiratory mortality., Conclusions: Deteriorated lung function predicts deaths. The reasons for impaired lung function should be medically explored to enable restoring measures aiming thus to prevent premature deaths.

Background: The continuing rise in asthma prevalence has been questioned, with recent reports suggesting a plateau., Aims: To assess a 10-year trend in the age-adjusted prevalence of physician-diagnosed asthma, respiratory and allergic symptoms, and use of asthma medication in the adult population of Helsinki during the Finnish Asthma Programme from 1994 to 2004., Methods: Two cross-sectional postal surveys were conducted among random Finnish National Population Registry samples 10 years apart using the same protocol. A total of 6,062 subjects (75.9%) and 2,449 subjects (61.9%) participated in 1996 and 2006, respectively., Results: The prevalence of physician-diagnosed asthma increased from 6.5% in 1996 to 10.0% in 2006 (p<0.001). This was evident in both genders aged <60 years, but particularly in women aged <40 years, paralleling an increased use of asthma medication. Concurrently, the prevalence of allergic rhinoconjunctivitis increased from 37.2% to 44.4% (p<0.001). The prevalence of physician-diagnosed chronic obstructive pulmonary disease remained unchanged (3.7%), while current smoking abated. Subjects with a smoking history had more respiratory symptoms (p<0.001). Among subjects without physician-diagnosed asthma, those reporting allergic rhinoconjunctivitis had a higher prevalence of lower respiratory tract symptoms., Conclusions: The prevalence of allergic rhinoconjunctivitis and physician-diagnosed asthma has increased in Helsinki during 10 years in adults, especially in women aged <40 years. Concomitantly, the use of asthma medication increased and subjects with physiciandiagnosed asthma were less symptomatic. The increase in the prevalence of physician-diagnosed asthma may partly be due to improved diagnostic recognition of asthma in primary care during the Finnish Asthma Programme, but the concurrent rise in allergic rhinoconjunctivitis may reflect a true rise in prevalence.

Introduction: Bronchial hyperresponsiveness (BHR) elevates the risk for development of respiratory symptoms and accelerates the decline in forced expiratory volume in the first second (FEV1 ). We thus aimed to assess the prevalence, determinants and quantity of BHR in Helsinki., Objectives: This study involved 292 randomly selected subjects age 26-66years, women comprising 58%., Methods: Following a structured interview, a spirometry, a bronchodilation test, and a skin-prick test, we assessed a bronchial challenge test with inhaled histamine using a dosimetric tidal breathing method. Results included the provocative dose inducing a decrease in FEV1 by 15% (PD15 FEV1 ) and the dose-response slope. For statistical risk factor-analyses, the severity of BHR was considered; PD15 values ≤1.6mg (BHR) and ≤0.4mg [moderate or severe BHR (BHRms )] served as cut-off levels., Results: BHR presented in 21.2% and BHRms in 6.2% of the subjects. FEV1<80% of predicted [odds ratio (OR) 4.09], airway obstruction (FEV1 /forced vital capacity<88% of predicted) (OR 4.33) and history of respiratory infection at age <5 (OR 2.65) yielded an increased risk for BHR as ORs in multivariate analysis. For BHRms , the determinants were decreased FEV1 below 80% of predicted (OR 27.18) and airway obstruction (OR 6.16). Respiratory symptoms and asthma medication showed a significant association with BHR., Conclusions: Of the adult population of Helsinki, 21% showed BHR to inhaled histamine. The main determinants were decreased FEV1 and airway obstruction. Quantitative assessment of BHR by different cut-off levels provides a tool for characterization of phenotypes of airway disorders in epidemiologic and clinical studies., (© 2011 Blackwell Publishing Ltd.)

Background: Asthma often begins in childhood or early adulthood and is a common disease among conscripts. The identification of long-term predictive factors for persistent asthma may lead to improved treatment opportunities and better disease control., Objective: Our aim was to study the prognostic factors of the severity of asthma among 40-year-old male conscripts whose asthma began in youth., Methods: We studied 119 conscripts who were referred to the Central Military Hospital during 1987-1990 due to asthma and who attended a follow-up visit approximately 20 years later. Asthma severity was evaluated during military service according to the medical records, and 20 years later during a follow-up visit using Global Initiative for Asthma guidelines. We used the results of lung function and allergy tests at baseline as predictors of current persistent asthma., Results: Compared with baseline, asthma was less severe at follow-up: 11.8% of subjects were in remission, 42.0% had intermittent asthma, 10.9% had mild persistent asthma, and 35.3% had moderate/severe persistent asthma (p < .001). In multivariate models, a positive exercise test at baseline yielded an odds ratio (OR) of 3.2 (95% CI 1.0-9.8, p = .046), a decreased FEV1/FVC % predicted an OR of 4.0 (95% CI 1.7-9.3, p = .002), and a decreased FEF50% % predicted an OR of 2.8 (95% CI 1.3-6.4, p = .012) for current persistent asthma., Conclusions: About half of the men had persistent asthma at the 20-year follow-up. Positive exercise tests and obstructive spirometry results were related to the persistence of asthma and may be useful long-term prognostic factors for asthma severity.

Objective: To examine the incidence of allergic rhinoconjunctivitis and asthma, and to assess allergic rhinoconjunctivitis as a risk factor for incident asthma, we performed a 11-year follow-up postal survey., Methods: The original study population was a random population sample of 8000 inhabitants of Helsinki aged 20-69 years in 1996. Participants in the first postal questionnaire survey, 6062 subjects, were invited to this follow-up study, and provided 4302 (78%) answers out of 5484 traced subjects in 2007., Results: Cumulative incidence of asthma from 1996 to 2007 was 4.0% corresponding to an annual incidence rate of 3.7/1000/year. After exclusion of those with asthma medication or physician-diagnosed chronic bronchitis or COPD at baseline in 1996, the cumulative incidence decreased to 3.5% (incidence rate 3.2/1000/year), and further to 2.7% (2.5/1000/year) when also those reporting recurrent wheeze or shortness of breath during the last year in 1996 were omitted from the population at risk. Remission of asthma occurred in 43 subjects and was 16.9% over 11 years. Cumulative 11-year incidence of allergic rhinoconjunctivitis was 16.9% corresponding to 16.8/1000/year, and cumulative remission was 18.1%. Incidence of allergic rhinoconjunctivitis was significantly lower among those who had lived in the countryside or on a farm during the first 5 years of life, but this was not true for asthma. In multivariate analysis, farm living during the first 5 years of life was protective for the development of allergic rhinoconjunctivitis, OR 0.75 (95%CI 0.57-0.99). Allergic rhinoconjunctivitis was a significant independent risk factor for incident asthma, OR 2.15 (95%CI 1.54-3.02). In the cohort, the prevalence of rhinoconjunctivitis increased from 38.0% in 1996 to 40.9% in 2007, physician-diagnosed asthma from 6.8% to 9.4%, while current smoking decreased from 31.3% to 23.3%., Conclusion: Incidence of allergic rhinoconjunctivitis was higher than in earlier studies, while asthma incidence remained on similar level, both being significantly higher in women. Allergic rhinoconjunctivitis doubled the risk for incident asthma., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Occupational exposures can cause adult-onset asthma. Early diagnosis and early avoidance of further exposure to causative agent improves the prognosis of occupational asthma. Occupational and primary care health services have an important role in the identification of new cases of occupational asthma. For the diagnosis of occupational asthma, serial peak expiratory flow (PEF) measurements should be performed in an early stage. Although it requires an effort from the patient, high quality recordings offer the best approach to assess the relationship between workplace exposure and respiratory symptoms. Good guidance and performance of serial PEF measurements in primary care is recommended and is worth the effort.

In a specific inhalation challenge (SIC) test the patient inhales an occupational agent in controlled environment and the subsequent asthmatic reaction is monitored. SIC is considered as the reference standard when confirming the diagnosis of sensitizer-induced occupational asthma. However, SIC is not always needed for the diagnosis; in many cases the causal relationship between an occupational agent and asthma can be shown also with serial peak flow measurements and specific immunologic testing. SIC is invaluable in identifying new occupational airway sensitizers. This is essential for preventing occupational asthma in the future.

Background: We aimed to assess the prevalence of allergic sensitization and multiple sensitization, risk factors, and the clinical impact of being sensitized in the adult population of Helsinki, Finland., Methods: As a part of the FinEsS study, a population-based random sample of 498 adults aged 26-60 years were tested for 15 common aeroallergens with skin prick tests (SPTs) and interviewed on respiratory symptoms and diseases, including respiratory irritants and childhood environment., Results: The prevalence of at least one positive prick test was 46.9%. A large difference by age was found: 56.8% were sensitized among those aged 26-39 years, 49.2% in the age group 40-49 years, and 35.6% in the age group 50-60 years (P<0.001). Sensitization to multiple allergens was common among young subjects with 42% of the sensitized responding to at least four allergens, while this proportion was only 16% of the sensitized among those aged 50-60 years. The prevalence of physician-diagnosed asthma, allergic rhinitis (AR) or conjunctivitis, and wheeze increased significantly with increasing number of positive responses to SPTs. Having a family history of AR or conjunctivitis was a significant risk factor for allergic sensitization and for sensitization to any of the pollens. Further, urban living in childhood yielded an increased risk for pollen sensitization., Conclusions: The prevalence of allergic sensitization was high in the urban adult population of Helsinki. More than half of those aged 26-39 years was sensitized and 24% was sensitized to at least four allergens. Sensitization to multiple allergens was associated with a high prevalence of asthma, AR or conjunctivitis, and wheeze.

Large differences in prevalence of asthma have been reported between westernised countries and the former Eastern European countries, and still no consensus about the reasons for the differences exists. The aim of this study was to assess diagnostic labelling of obstructive airway diseases, comparing subjects with respiratory symptoms and the diagnoses obtained in Estonia, Finland, and Sweden. A postal questionnaire was sent to population-based random samples, and 44,483 (76%) answers were obtained from the 58,661 invited in 1996. Among men, current smoking was most common in Estonia, 60%, followed by Finland, 39%, and Sweden, 28%. In all three countries, 30% of women were current smokers. Most respiratory symptoms including wheezing were most common in Estonia, also among non-smokers. The prevalence of asthma was 2.0% and chronic bronchitis 10.7% in Estonia, while the opposite was found in Sweden with an asthma prevalence of 7.8% and a chronic bronchitis prevalence of 3.1%. The pattern in Finland was similar to that of Sweden. The same differences between the three countries were found also among young subjects. The total proportion of diagnosed obstructive lung diseases in subjects with respiratory symptoms was similar, but the diagnosis of asthma was considerably more common in Finland and Sweden. Chronic bronchitis was favoured in Estonia, also among young adults irrespectively of what symptoms were present. In a multivariate model with correction for confounders, the risk (OR) for having a diagnosis of asthma was 5.65 (95% CI: 4.86-6.56) when living in Sweden, and 3.51 (95% CI: 3.00-4.12) in Finland, whereas risk for chronic bronchitis was 0.28 (0.25-0.31) and 0.22 (0.19-0.25), respectively, compared to Estonia. The study indicates differences in diagnostic practices of obstructive lung diseases between the three countries.

Objective: To assess the relation of socio-economic status to respiratory symptoms common in asthma and chronic bronchitis, and to compare risk factors for these symptoms between three neighbouring countries., Design: A postal survey was performed in 1996 as a part of comparative studies in Finland, Sweden and Estonia (the FinEsS studies). A random sample of 58,661 subjects aged 20-64 years were invited, of whom 44,483 participated., Results: Respiratory symptoms were most prevalent among manual workers, who were at significantly increased risk for chronic respiratory symptoms. The same pattern of increased risk appeared when the analyses were made among non-smokers only: for recurrent wheeze, manual workers in industry yielded an OR of 1.91 (95%CI 1.62-2.24) and in the service sector an OR of 1.50 (95%CI 1.27-1.78). The corresponding figures for chronic productive cough were 1.45 (95%CI 1.22-1.71) and 1.20 (95%CI 1.02-1.42), respectively. Risk factor profiles for respiratory symptoms were similar in Finland, Sweden and Estonia, except for gender differences in Estonia., Conclusions: Belonging to the socio-economic group of manual workers correlated with an increased risk for chronic respiratory symptoms, independently of smoking habits, in each country. Women manual workers in industry suffered most from respiratory symptoms.

The aim of this part of the FinEsS-studies was to assess whether differences existed in prevalence of asthma, chronic bronchitis, and respiratory symptoms between three Baltic capitals, and to examine risk factor profiles for respiratory conditions. In 1996, a postal survey was performed in these cities with a response rate of 72% in Stockholm, 76% in Helsinki, and 68% in Tallinn. The prevalence of physician-diagnosed asthma was 76% in Stockholm, 6.2% in Helsinki, and 2.3% in Tallinn, while respiratory symptoms were most common in Tallinn. The prevalence of physician-diagnosed chronic bronchitis was 10.6% in Tallinn, 3.4% in Helsinki, and 3.0% in Stockholm. Risk factor analyses revealed a significantly increased risk for those living in Tallinn compared to that of Stockholm for wheezing conditions, OR 1.56-1.69, longstanding cough, OR 1.92 (1.74-2.13), attacks of shortness of breath during the previous 12 months, OR 1.35 (1.20-1.52), and chronic productive cough, OR 1.49 (1.28-1.74). Subjects having symptoms common in asthma were more likely to have physician-diagnosed asthma in Stockholm and Helsinki than in Tallinn, while subjects having bronchitis symptoms had more often physician-diagnosed chronic bronchitis in Tallinn. Prevalence of respiratory symptoms was higher in Tallinn than in Stockholm and Helsinki, while physician-diagnosed asthma was more common in Stockholm and Helsinki. The prevalence of physician-diagnosed chronic bronchitis was three times as high in Tallinn as in Helsinki or Stockholm. Our results also suggest large differences in diagnostic practices between the three countries, while the differences between the capitals in true prevalence of disease may be small.

We have compared data from northern and southern Finland in a large epidemiological survey on respiratory conditions. The aim was to compare the prevalence of respiratory symptoms, asthma, and chronic bronchitis in northern and southern Finland. The study was a part of comparative studies in Finland, Estonia, and Sweden, the FinEsS studies. Data from a postal survey on subjects aged 20-69 was analyzed. Participation rate was 84% of 7937 invited in Lapland in the north, and 77% of 7877 in Helsinki in the south. Physician-diagnosed asthma was reported by 5.6% in Helsinki, and by 5.5% in Lapland. Symptoms common in asthma were also equally prevalent in the two areas. Hay fever was significantly more common in Helsinki, 36% vs. 26% (p < 0.001). The prevalence for physician-diagnosed chronic bronchitis was not significantly higher in Helsinki (3.4%) than in Lapland (2.9%). Those working outdoors reported more bronchitic symptoms than people working indoors (p < 0.05). Respiratory symptoms provoked by pollen or animal dander were more common in Helsinki, while symptoms provoked by inhaled irritants or cold weather conditions were more prevalent in Lapland. Current smoking was equally prevalent: 37% in Lapland and 38% in Helsinki. Risk factor analysis showed an elevated risk for chronic productive cough for living in Helsinki (OR 1.32), however, increasing age and current smoking were the strongest risk factors. In conclusion, prevalence of asthma and asthma-related symptoms was similar in southern and northern Finland, but chronic bronchitis and bronchitic symptoms were more common in Helsinki, and the highest prevalence was found among current smokers working outdoors. Respiratory symptoms in cold weather were more prevalent in the north, while hay fever and respiratory symptoms provoked by allergens were more common in the south. The results support the view that environmental factors have a substantial effect on respiratory symptoms, but less effect on the prevalence of asthma.

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.