Occupational risk factors for airway obstruction in a population-based study in Northern Europe.

BACKGROUND: Airway obstruction is a key feature of asthma and chronic obstructive pulmonary diseases (COPD). Smoking habits and workplace exposures to vapors, gas, dusts, and fumes (VGDF) could cause or exacerbate airway obstruction. The aim of this study is to evaluate the risk of airway obstruction due to smoking and workplace exposure, and their interaction, in a large population-based study. METHODS: In this cross-sectional study, a sample (n = 6153) of the Swedish population aged between 24 and 76 years underwent a questionnaire, clinical examination, blood test, and spirometry to gather information on airway obstruction classified by Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria or American Thoracic Society (ATS)/European Respiratory Society (ERS) criteria, risk factors, and confounders. Occupational exposures to VGDF were rated according to a specific job-exposure matrix. Adjusted logistic regression models were used to evaluate risk factors for airway obstruction in smokers and nonsmokers. RESULTS: In total, 9.8% had airway obstruction by GOLD criteria and 10.3% by ATS/ERS. Smokers with a high likelihood of exposure to VGDF had a higher risk of airway obstruction than those not exposed (odds ratio [OR]: 1.74, 95% confidence interval [CI]: 1.15-2.65 by GOLD; OR: 1.58, 95% CI: 1.06-2.37 by ATS/ERS) especially those >50 years of age. In smokers highly exposed to VGDF, risk estimates were higher than in the whole population, and the interaction between high exposure to VGDF and smoking further increased the risk of airway obstruction. CONCLUSIONS: This study suggests a possible role for interaction between cigarette smoking and VGDF exposure on the risk of airway obstruction.

Assessment of Global Lung Function Initiative (GLI) reference equations for diffusing capacity in relation to respiratory burden in the Swedish CArdioPulmonary bioImage Study (SCAPIS).

The Global Lung Function Initiative (GLI) has recently published international reference values for diffusing capacity of the lung for carbon monoxide (D LCO). Lower limit of normal (LLN), i.e. the 5th percentile, usually defines impaired D LCO We examined if the GLI LLN for D LCO differs from the LLN in a Swedish population of healthy, never-smoking individuals and how any such differences affect identification of subjects with respiratory burden.Spirometry, D LCO, chest high-resolution computed tomography (HRCT) and questionnaires were obtained from the first 15 040 participants, aged 50-64 years, of the Swedish CArdioPulmonary bioImage Study (SCAPIS). Both GLI reference values and the lambda-mu-sigma (LMS) method were used to define the LLN in asymptomatic never-smokers without respiratory disease (n=4903, of which 2329 were women).Both the median and LLN for D LCO from SCAPIS were above the median and LLN from the GLI (p<0.05). The prevalence of D LCO GLI LLN but GLI LLN but GLI LLN and >SCAPIS LLN). No differences were found with regard to physician-diagnosed asthma.The GLI LLN for D LCO is lower than the estimated LLN in healthy, never-smoking, middle-aged Swedish adults. Individuals with D LCO above the GLI LLN but below the SCAPIS LLN had, to a larger extent, an increased respiratory burden. This suggests clinical implications for choosing an adequate LLN for studied populations.

Restrictive spirometric pattern and true pulmonary restriction in a general population sample aged 50 - 64 years.

BACKGROUND: There is low diagnostic accuracy of the proxy restrictive spirometric pattern (RSP) to identify true pulmonary restriction. This knowledge is based on patients referred for spirometry and total lung volume determination by plethysmograpy, single breath nitrogen washout technique or gas dilution and selected controls. There is, however, a lack of data from general populations analyzing whether RSP is a valid proxy for true pulmonary restriction. We have validated RSP in relation to true pulmonary restriction in a general population where we have access to measurements of total lung capacity (TLC) and spirometry. METHODS: The data was from the Swedish CArdioPulmonary bioImage Study (SCAPIS Pilot), a general population-based study, comprising 983 adults aged 50-64. All subjects answered a respiratory questionnaire. Forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were obtained before and after bronchodilation. TLC and residual volume (RV) was recorded using a body plethysmograph. All lung function values are generally expressed as percent predicted (% predicted) or in relation to lower limits of normal (LLN). True pulmonary restriction was defined as TLC < LLN5 defined as a Z score < - 1.645, i e the fifth percentile. RSP was defined as FEV1/FVC ≥ LLN and FVC < LLN after bronchodilation. Specificity, sensitivity, positive and negative likelihood ratios were calculated, and 95% confidence intervals (CIs) were calculated. RESULTS: The prevalence of true pulmonary restriction was 5.4%, and the prevalence of RSP was 3.4%. The sensitivity of RSP to identify true pulmonary restriction was 0.34 (0.20-0.46), the corresponding specificity was 0.98 (0.97-0.99), and the positive likelihood ratio was 21.1 (11.3-39.4) and the negative likelihood ratio was 0.67 (0.55-0.81). CONCLUSIONS: RSP has low accuracy for identifying true pulmonary restriction. The results support previous observations that RSP is useful for ruling out true pulmonary restriction.

Pain could negatively affect school grades - Swedish middle school students with low school grades most affected.

Recurrent headache, abdominal and musculoskeletal pain are common in adolescents and it is therefore important to understand their impact on the transitional period from childhood to adulthood. However, studies of the prevalence over time and implications on educational outcomes are still limited, especially regarding multiple pain symptoms. The present study material consists of questionnaire surveys, completed in 2000 and 2008, including two study populations of 9th grade adolescents aged 15 living in West Sweden (n = 20 877). Pain symptoms and demographic variables were based on self-reports from the questionnaires, and school grades were obtained from Statistics Sweden after the student had finished their 9th grade. Between 2000 and 2008, the prevalence of abdominal pain increased among Swedish adolescents (largest increase in girls); the prevalence of headache increased only in girls; the prevalence of pain in upper body decreased only in boys. School grades were significantly lower among those with headache or abdominal pain. Among students with low school grades (10th percentile) the estimated difference between those having any of the symptoms or none were -27 school grade units (95% confidence interval for girls (-27.8; -26.0), for boys (-27.6; -25.5). Both symptoms being present pronounced the association. Low parental education increased the negative effect of symptoms on school grades, most pronounced in the group with the lowest grades. In conclusion, identification of pain symptoms may improve academic achievements, especially in students with multiple symptoms and with parents having low education. Further intervention studies are need.

Spirometric reference equations for Swedish adults.

New spirometric reference equations for Swedish adults are required. Three different older sets of reference equations clinically used in Sweden have various drawbacks and the recently published 'The Global Lung Function 2012 (GLI) equations' have been shown not to be adequate for Swedish normal, healthy non-smokers. We have recently concluded that a piecewise linear model presented by Lubinski and Gólczewski accurately describes the distribution of spirometric variables in a large Swedish random population sample. This piecewise linear model also offers the important advantage of implementing easily physiologically interpretable coefficients. The present study aimed at presenting piecewise linear reference equations for Swedish adults based on a random population sample of 6685 individuals aged 25-75 years. Predicted normal values by the piecewise linear reference equations and lower limit normal (LLN) were compared with the three reference equations frequently used clinically in Sweden and the GLI equations. We found predicted normal values according to the present piecewise linear reference equations close to 100% predicted normal as expected, whereas the other equations either overestimated or underestimated normal subjects. Concerning LLN, the present equations, i.e. 1·645 × RSD, showed the least deviation from the expected 5% and, e.g., the GLI equations systematically identified too few subjects below LLN. We conclude that the present piecewise linear reference equations, based on a relatively large general population sample, ought to be considered for clinical use in Sweden. Application of 1·645 × RSD below predicted value gave an acceptably accurate LLN.

Dietary intake, leisure time activities and obesity among adolescents in Western Sweden: a cross-sectional study.

BACKGROUND: Overweight and obesity among adolescents are increasing worldwide. Risk factors include dietary intake characteristics and high levels of physical inactivity. In Sweden, few large comprehensive population-based surveys of dietary intake and lifestyle among adolescents have been carried out. Thus, the purpose of the current study was to describe dietary intake and food choices as well as leisure time activities in relation to overweight and obesity in a total sample of all schoolchildren aged 15 years in Western Sweden. METHODS: In 2008, a questionnaire was sent to all 21,651 adolescents born in 1992 in Västra Götaland Region, Sweden. Participation rate was 54.3 % (50.7 % girls/49.3 % boys). The questionnaire included a 73-item semi-quantitative food frequency questionnaire and questions on lifestyle. Results were evaluated against the Nordic Nutrition Recommendations and Swedish indicators of healthy diet and exercise habits. Associations with concurrent overweight and obesity were evaluated in multiple linear regression analysis. RESULTS: Among girls, 49.5 % reached the goal of consuming fruit and vegetables at least daily, whereas for boys the figure was 34.4 %. Among both sexes, 15 % reached the goal of consuming fish at least twice weekly. Two-thirds of both sexes reached the goal of regular moderate or vigorous physical activity weekly. In total, 12.4 % were overweight and 2.4 % were obese. More girls than boys were underweight, whereas more boys than girls were overweight or obese (p < 0.001). Boys exhibited a more frequent intake of sodas and concentrated fruit juices, milk 3 % fat, bread and potatoes and fast food (p < 0.001). Frequent intake of candies and chocolate was reported by both sexes. Among girls and boys, living in rural areas, living in apartments and reporting no frequent leisure time physical activity were significant risk factors for being overweight or obese, also when adjusted for other risk factors. CONCLUSIONS: Dietary habits of adolescents in Western Sweden warrant improvements. Public health actions should be taken to increase consumption of fruit, vegetables and fish, and decrease consumption of sodas and candies and also to increase frequency of physical activity. These actions may be helpful in reducing risks for overweight and obesity.

A physiologically based model for spirometric reference equations in adults.

A spirometric reference equation consists of a mathematical model with constants and coefficients optimized to fit a specific data set from healthy individuals. Commonly applied models are selected on statistical rather than physiological considerations. A predetermined model with constants and coefficients optimized to various populations would enable interpretable and interesting comparisons between populations. Lubinski and Gólczewski recently presented a piecewise linear model with constants and coefficients claimed to be physiologically interpretable (Lubinski model). Three questions were addressed: Is the Lubinski model as useful clinically as other models: multiple linear, piecewise polynomial and exponential with splines? Will reference equations based on the Lubinski model and optimized to a Swedish and to a Polish population allow for interpretable comparisons? Are three well-known reference equations clinically useful in the Swedish adult population? A recent Swedish random population sample with high-quality spirometric measurements enabled the present analyses. When optimized to fit the Swedish population sample, the Lubinski model and two other models provided accurate predictive normal values. Interesting differences were demonstrated between the Polish and Swedish populations. The proportion of subjects below lower limit normal was adequate for the piecewise polynomial equations but too low and not clinically useful for the advocated exponential equations with splines. It is concluded that the Lubinski model is clinically as useful as other models, and it adds important value and is recommended for future spirometric reference equations for adults. The advocated exponential equations with splines are not recommended for Swedish adults because of too wide normal limits.

Trends in the prevalence of asthma, rhinitis, and eczema in 15 year old adolescents over an 8 year period.

BACKGROUND: Trends in prevalence of asthma and allergic diseases are still controversial, and rarely studied among adolescents at midpoint of puberty. METHODS: In 2000, a questionnaire was mailed to adolescents (n = 18,158) attending 9th grade at school and living in Västra Götaland County, Sweden. Eight years later, the same questionnaire was mailed to adolescents (n = 21,651), using identical inclusion criteria as previously. Altogether, 10,837 adolescents completed the questionnaire in 2000 and 11,754 in 2008. Differences in prevalence of physician diagnosed asthma, asthma symptoms, rhinitis, and eczema between the periods were analyzed by Chi-square test. Multiple logistic regression models were performed to test for trends in prevalence of these diseases, adjusting for potential confounders. RESULTS: Physician diagnosed asthma and lifetime and current rhinitis were increased in 2008, while wheeze decreased (p < 0.05). Taking sex, foreign descent, body mass index, and parents' education into account, the prevalence of physician diagnosed asthma (OR 1.3 [95% CI 1.2-1.4]) and lifetime (1.7 [1.6-1.8]) and current rhinitis (1.5 [1.4-1.6]) had increased. Eczema had decreased (0.9 [0.8-0.98]). These trends were consistent in boys and girls, but more prominent in those with obesity. In physician diagnosed asthmatics, there was no change in wheeze, asthma symptoms, or asthma medication. CONCLUSIONS: The prevalence of physician diagnosed asthma has increased over the last decade, maybe due to combinations of changes in diagnostics and increased general awareness, rather than a real increase. Results showed an increase in rhinitis and a decrease in eczema. Obesity seems to have a modifying effect, which calls for further investigation.

Validity of a questionnaire-based diagnosis of chronic obstructive pulmonary disease in a general population-based study.

BACKGROUND: The diagnosis of chronic obstructive pulmonary disease (COPD) is based on airflow obstruction. In epidemiological studies, spirometric data have often been lacking and researchers have had to rely almost solely on questionnaire answers. The aim of this study is to assess the diagnostic accuracy of questionnaire answers to detect COPD. METHODS: A sample of the Swedish general population without physician-diagnosed asthma was randomly selected and interviewed using a respiratory questionnaire. All eligible subjects aged 25-75 years (n = 3892) performed spirometry for detection of airflow obstruction using Global Initiative for Chronic Obstructive Lung Disease (GOLD) or American Thoracic Society (ATS)/European Respiratory Society (ERS) criteria. Sensitivity, specificity, positive likelihood ratio (LR+), positive predictive values (PPVs), and negative predictive values (NPVs) were calculated to define diagnostic accuracy of questionnaire answers. RESULTS: The sensitivity of the question "Have you been diagnosed by a physician as having COPD or emphysema?" in detecting airflow obstruction was 5.7% using GOLD, and 9.8% using ATS/ERS, criteria; specificity was 99.7% for GOLD and 99.5% for ATS/ERS. Sensitivity, specificity, and PPV were higher for the question compared to self-reported symptoms of chronic bronchitis in identifying subjects with airflow obstruction. CONCLUSIONS: The high specificity and good PPV suggest that the question "Have you been diagnosed by a physician as having COPD or emphysema?" is more likely to identify those who do not have airflow obstruction, whereas the low sensitivity of this question could underestimate the real burden of COPD in the general population.

Occupational chronic obstructive pulmonary disease: a systematic literature review.

OBJECTIVE: Occupational-attributable chronic obstructive pulmonary disease (COPD) presents a substantial health challenge. Focusing on spirometric criteria for airflow obstruction, this review of occupational COPD includes both population-wide and industry-specific exposures. METHODS: We used PubMed and Embase to identify relevant original epidemiological peer-reviewed articles, supplemented with citations identified from references in key review articles. This yielded 4528 citations. Articles were excluded for lack of lung function measurement, insufficient occupational exposure classification, lack of either external or internal referents, non-accounting of age or smoking effect, or major analytic inadequacies preventing interpretation of findings. A structured data extraction sheet was used for the remaining 147 articles. Final inclusion was based on a positive qualitative Scottish Intercollegiate Guidelines Network (SIGN) score (≥2+) for study quality, yielding 25 population-wide and 34 industry/occupation-specific studies, 15 on inorganic and 19 on organic dust exposure, respectively. RESULTS: There was a consistent and predominantly significant association between occupational exposures and COPD in 22 of 25 population-based studies, 12 of 15 studies with an inorganic/mineral dust exposure, and 17 of 19 studies on organic exposure, even though the studies varied in design, populations, and the use of measures of exposure and outcome. A nearly uniform pattern of a dose-response relationship between various exposures and COPD was found, adding to the evidence that occupational exposures from vapors, gas, dust, and fumes are risk factors for COPD. CONCLUSION: There is strong and consistent evidence to support a causal association between multiple categories of occupational exposure and COPD, both within and across industry groups.

[Occupational exposure for dust and gases is an important risk factor for developing COPD]. / Erhvervseksposition for støv og dampe er en betydende risikofaktor for KOL.

Some patients with chronic obstructive pulmonary disease (COPD) are never-smokers, which suggests that there must be other important risk factors. This paper describes the evidence for an association between occupational exposure and COPD. In several studies a consistent and predominantly significant association between occupational exposures and COPD is found, even though the studies vary in design, enrolled populations and in measures of exposure and outcome. Strong evidence supports a causal association between multiple categories of occupational exposure and COPD, both within and across industry groups.

Dissociation of dysfunctional breathing and odour intolerance among adults in a general-population study.

BACKGROUND: Many patients present with a mixture of respiratory problems such as shortness of breath, heavy breathing, coughing and odour intolerance. If these patients are diagnosed as asthma, it might sometimes be a false diagnosis. Concepts such as sensory hyperreactivity, hyperventilation, asthma-like symptoms, odour intolerance and dysfunctional breathing are used to refer to these patients. Non-respiratory symptoms such as headache, fatigue and bloating are sometimes also part of the clinical picture. Our aim was to use factor analysis to increase our understanding of breathing-related symptoms in a general-population frame. METHODS: A respiratory questionnaire was answered by 10 108 subjects in a general-population sample. Items aiming to identify individuals with breathing-related symptoms and asthma were included. We used factor analysis with Varimax rotation to extract discriminatory components (i.e. groups of symptoms), based on the questionnaire items. The aim was to find groups of items (factors) as distinct as possible, still allowing overlap and showing the importance of each item in the separated factor. RESULTS: Five distinct factors were identified in the factor analysis, representing dysfunctional breathing, odour intolerance, asthma, bronchitis and a group with mixed symptoms, respectively. These five factors explained 55% of the variance. CONCLUSIONS: Based on our findings, we conclude that non-asthmatic breathing-related symptoms may be separated into at least two categories in a general population, odour intolerance and dysfunctional breathing. These two categories seem to be two distinct groups of subjects with breathing-related symptoms and may represent different clinical entities separated from asthma and bronchitis.

A feasible lifestyle program for early intervention in patients with chronic obstructive pulmonary disease (COPD): a pilot study in primary care.

AIM: To evaluate the feasibility of a lifestyle program for early intervention in patients with COPD in a primary care population. METHODS: The study was performed in a Primary Health Care Centre in Western Sweden. During a four-week period, all smokers between 40-70 years of age were invited to answer a questionnaire and to perform spirometry. The intervention program included a specially designed smoking cessation program and programs for physical activity and diet. RESULTS: 84 smokers were included. 42% fulfilled the criteria for COPD. All of the COPD patients were in GOLD stage I and II. Among the COPD subjects, 38% were underweight and 56% had a low fat-free mass - both together indicating malnutrition and the need for nutritional treatment. By the end of the intervention program, 47% of the COPD patients had stopped smoking. CONCLUSIONS: The intervention program was feasible and effective with a very high smoking cessation rate.

Fish intake of Swedish male adolescents is a predictor of cognitive performance.

AIM: Fish intake is reported to positively influence cognitive performance in infants and the elderly. In a longitudinal cohort study, we evaluated how fish consumption related to later cognitive performance in healthy young male adolescents. METHODS: In 2000, all 15-year-olds (n = 18 158; 9260 males) in the western region of Sweden were requested to complete an extensive questionnaire with items on diseases, fish consumption and socioeconomic status. Questionnaire data from the male responders (n = 4792, response rate 52%) were linked with records on subsequent intelligence test performance at age 18 from the Swedish Military Conscription Register (n = 3972). Multivariate linear models were used to estimate associations between fish intake and cognitive performance, adjusting for potential confounders. RESULTS: There was a positive association between the number of times having fish meals per week at age 15 and cognitive performance measured 3 years later. Fish consumption of more than once per week compared to less than once per week was associated with higher stanine scores in combined intelligence (0.58 units; 95% confidence interval 0.39, 0.76), in verbal performance (0.45; 0.27, 0.63) and in visuospatial performance (0.50; 0.31, 0.69). The association between fish consumption and the 3 intelligence scores was the same in lowly and highly educated groups. This indicates that education did not influence the association between the frequency of fish meals consumed and cognitive performance. CONCLUSION: Frequent fish intake at age 15 was associated with significantly higher cognitive performance 3 years later.

Management of chronic obstructive pulmonary disease (COPD) in primary care: a questionnaire survey in western Sweden.

AIM: To assess the primary care management of chronic obstructive pulmonary disease (COPD) in relation to COPD guidelines. METHOD: A postal questionnaire was sent out to all Primary Health Care Centres (PHCCs) in western Sweden (n=232). The response rate was 75%. RESULTS: A majority of the PHCCs had a nurse and physician responsible for COPD care. They used spirometry equipment regularly, but only 50% reported that they calibrated it at least weekly. Less than 30% of the PHCCs reported access to a dietician, occupational therapist or physiotherapist. There was a structured smoking cessation program in 50% of the PHCCs. Larger PHCCs were more likely to use spirometry equipment regularly and to have specific personnel for COPD care. CONCLUSION: There is a need to establish structured programs for COPD care including smoking cessation programs for COPD patients with special trained staff. Larger PHCCs have a better infrastructure for providing guideline-defined COPD care.

Nasal symptoms are associated with school performance in adolescents.

Children with asthma and allergy have higher school absence rates than others, but little is known about their school performance. In a study of 9538 adolescents, nasal symptoms severe enough to affect daily activity were associated with low-grade sum, particularly in adolescents using anti-allergy medication.

Incidence of hand eczema in female Swedish hairdressers.

OBJECTIVE: To estimate the occurrence of hand eczema in hairdressers in Sweden. METHODS: The occurrence of hand eczema was estimated in a Swedish longitudinal retrospective cohort study including all female graduates from vocational schools for hairdressers from 1970 to 1995. A stratified sample from the general population acted as controls. A self-administered questionnaire including questions on the occurrence of hand eczema, skin atopy, working periods and number of hair treatments performed per week was sent to the participants. Incidence rate ratios (IRRs) of hand eczema were estimated. RESULTS: The incidence rate of hand eczema in hairdressers was 23.8 cases/1000 person-years, whereas in hairdressers who were aged <25 years it was 37.1/1000 person-years. The corresponding IRR for hairdressers compared with controls was 2.5 (95% confidence interval (CI) 2.2 to 2.8), and that for younger hairdressers was 3.1 (95% CI 2.6 to 3.5). The mean age at onset of hand eczema was 21.6 years for hairdressers and 21.2 years for controls. The 1-year prevalence of hand eczema was 18.0% for hairdressers and 12.1% for controls. A large number of hair treatments involving exposure to skin irritants and sensitisers were reported. The incidence rate of hand eczema was higher among individuals with a history of childhood eczema, both for hairdressers and for controls, giving an (age-adjusted) IRR of 1.9 and 2.2, respectively. The attributable fraction of hand eczema from skin atopy was 9.6%. A synergistic effect of skin atopy and hairdressing was found on the occurrence of hand eczema. The relative excess risk due to interaction was 1.21 (95% CI 0.21 to 2.21; p = 0.01). CONCLUSION: Hairdressers are highly exposed to skin-damaging substances. The self-reported incidence of hand eczema was substantially higher in female hairdressers than in controls from the general population and than that found previously in register-based studies. For many individuals, onset of hand eczema occurs early in life. Only about 10% of the hand eczema cases among hairdressers would be prevented if no one with skin atopy entered the trade.

Occupational skin exposure and hand eczema among dental technicians-need for improved prevention.

OBJECTIVES: The aims of this study were to estimate occupational skin exposure, the use of skin protection, and the incidence of hand eczema among dental technicians. METHODS: In a retrospective cohort study, dental technicians (N=2139) and randomly selected population controls (N=2288) received a postal questionnaire on occupational skin exposure, protective glove use, and hand eczema, including the year of onset. The response rate was 57% for the dental technicians and 58% for the controls. RESULTS: Altogether 80% of the dental technicians reported skin exposure to uncured (meth)acrylates (MA), and 87% had skin contact with grinding dust from MA. Thirty-nine percent used protective gloves when handling uncured MA. Twenty-two percent of the currently employed technicians reported participation in obligatory training concerning the handling of thermosetting plastics, and 58% did not know how long normally used gloves protected the skin against uncured MA. Altogether 48% of the dental technicians and 30% of the controls reported more than 10 hand washings a day (P<0.001). For the dental technicians, the incidence of hand eczema was 8.5 cases/1000 person-years during MA-exposed time. For the controls, the incidence was 3.3. The incidence rate ratio for the men was 3.6 (95% CI 2.3-5.6), and for the women it was 2.4 (95% CI 1.7-3.3). CONCLUSIONS: The work of dental technicians involves frequent and unprotected exposure to MA and frequent hand washings. Dental technicians have twice the risk of hand eczema than the general population. Efforts to improve skin protection and increase participation in obligatory training about handling thermosetting plastics are important.

The incidence of respiratory symptoms in female Swedish hairdressers.

BACKGROUND: Airway diseases in hairdressers are a concern. The objective of this investigation is to evaluate the risk for three respiratory symptoms, wheeze, dry cough, and nasal blockage, in hairdressers. METHODS: A questionnaire on respiratory symptoms, atopy, smoking, and work history was answered by 3,957 female hairdressers and 4,905 women from the general population as referents. Incidence rates (IR) and incidence rate ratios (IRRs) for the three symptoms were estimated. RESULTS: The IRs of all three studied symptoms were higher in the hairdressers compared with the referents. Smoking modified the effects of cohort affiliation for all three symptoms; the combined effect from hairdressing work and smoking was less than expected. In addition, the effect of cohort affiliation for wheeze was also modified by atopy, and the effect of cohort affiliation for nasal blockage was also modified by calendar year. CONCLUSIONS: Hairdressing work was associated with increased incidences of respiratory symptoms. Smoking had a negative modifying effect.