Atopy in people aged 40 years and over: Relation to airflow limitation.

BACKGROUND: Previous studies have reached conflicting conclusions about the role of atopy as a risk factor for COPD. In part, this is attributable to variation in the definitions of airflow limitation and the treatment of people with asthma. OBJECTIVE: To establish whether there is any independent association between atopy and post-bronchodilator airflow limitation in the general population aged 40 years and over. METHODS: A cross-sectional survey was conducted in a general population sample of 2415 people aged 40 years and over in Australia. A history of ever being diagnosed with asthma was elicited by questionnaire. Atopy was defined as any skin prick test weal to common aeroallergens ≥4 mm. Airflow limitation was defined as post-bronchodilator spirometric (FEV1 /FVC) ratio

Adherence to asthma management guidelines by middle-aged adults with current asthma.

BACKGROUND: With the increasing burden of asthma worldwide, much effort has been given to developing and updating management guidelines. Using data from the Tasmanian Longitudinal Health Study (TAHS), the adequacy of asthma management for middle-aged adults with asthma was investigated. METHODS: Information about spirometry, medication history and current asthma status was collected by the most recent TAHS when participants were in their mid 40s. Only those who reported ever having asthma were eligible for analysis. RESULTS: Of the 702 participants who reported ever having asthma, 50% had current asthma (n = 351) of whom 71% were categorised as having persistent asthma (n = 98 mild, n = 92 moderate, n = 58 severe). The majority (85.2%) of participants with current asthma had used some form of asthma medication in the past 12 months, but the proportion of the use of minimally adequate preventer medication was low (26%). Post-bronchodilator airflow obstruction increased progressively from mild to severe persistent asthma for those inadequately managed, but not for those on adequate therapy. CONCLUSION: Appropriate use of asthma medication by this middle-aged group of adults with current asthma was inadequate, especially for those with adult-onset moderate or severe persistent disease and without a family history of asthma. These results suggest that proper use of preventer medication could protect against the progressive decline in lung function associated with increasing severity. This has implications not just for poor quality of life, but also for the development of fixed airflow obstruction.

Relevance of the hygiene hypothesis to early vs. late onset allergic rhinitis.

INTRODUCTION: The hygiene hypothesis proposes that reduced exposure to infections in early life increases the risk of developing allergic conditions including allergic rhinitis. We examined the association between markers of the hygiene hypothesis and allergic rhinitis that developed before 7 years of age and allergic rhinitis that developed after 7 years of age. METHODS: The Tasmanian Longitudinal Health Study (TAHS) is a population-based cohort (n=8583) study of respiratory disease. Participants have been followed from 7 to 44 years of age. Information on potential risk factors, allergies and respiratory symptoms was collected longitudinally. Using multi-nomial logistic regression, exposure to siblings, infections, tonsillectomy and farm residence during childhood were examined as risk factors for allergic rhinitis that developed before or after 7 years of age. All analyses were adjusted for gender, maternal and paternal atopy, mother's age at participant's birth, paternal socio-economic status in 1968 and personal socio-economic status in 2004. RESULTS: Greater cumulative exposure to siblings before the age of 2 years was strongly inversely associated with early onset allergic rhinitis (<1 year sib exposure: OR=0.6, 95% CI 0.3-1.0; 1-3 years sib exposure: OR=0.6, 95% CI 0.4-0.9; >3 years sib exposure: OR=0.4, 95% CI 0.3-0.8) less so with later onset allergic rhinitis. The risk of early onset allergic rhinitis decreased with increasing viral infections (OR=0.7, 95% CI 0.5-0.9) during childhood. Having a tonsillectomy before 7 years of age increased the risk of early onset allergic rhinitis (OR=1.7, 95% CI 1.2-2.5). None of these factors was associated with later onset allergic rhinitis. CONCLUSIONS: Exposures relevant to the hygiene hypothesis were important predictors for the development of early onset but less so for later onset allergic rhinitis. The exact mechanisms by which siblings and infections protect against allergic rhinitis are unclear. The stronger findings for earlier onset allergic rhinitis suggest that family structure and infections have most impact on disease risk in early life. Further research should focus on early onset allergic rhinitis when exploring causal explanations for any sibling effect.

Prediction equations for single breath diffusing capacity (Tlco) in a middle aged caucasian population.

BACKGROUND: There are many reference equations for the measurement of single breath carbon monoxide diffusing capacity of the lung (Tlco). However, the testing methodologies vary and there are no well documented studies that have developed reference equations for Tlco and alveolar volume (Va) in middle aged and older populations. AIMS: (1) Develop reference equations for Tlco in a middle aged population using the current American Thoracic Society/European Respiratory Society (ATS/ERS) guidelines; (2) compare the equations with those commonly used in laboratories around the world. METHODS: Healthy subjects (498 male and 474 female) aged 45-71 years were recruited as part of a larger epidemiological study. All participants completed a respiratory questionnaire and had spirometry and single breath Tlco (corrected for haemoglobin) measurements following ATS/ERS guidelines. RESULTS: Mean age was 58 years for males and 57 years for females. For males, factors that predicted Tlco were: height, age, agexheight interaction and being an ex-smoker. For females, factors that predicted Tlco were: height, age, weight and an agexheight interaction. CONCLUSION: We have described new prediction equations for Tlco in a middle aged population that require validation in other populations.

A mixed methods study to compare models of spirometry delivery in primary care for patients at risk of COPD.

BACKGROUND: To increase recognition of airflow obstruction in primary care, we compared two models of spirometry delivery in a target group at risk of chronic obstructive pulmonary disease (COPD). METHODS: A 6 month qualitative/quantitative cluster randomised study in eight practices compared opportunistic spirometry by "visiting trained nurses" (TN) with optimised "usual care" (UC) from general practitioners (GPs) for smokers and ex-smokers, aged over 35 years. Outcomes were: spirometry uptake and quality, new diagnoses of COPD and GPs' experiences of spirometry. RESULTS: In the eligible target population, 531/904 (59%) patients underwent spirometry in the TN model and 87/1130 (8%) patients in the UC model (p < 0.0001). ATS spirometry standards for acceptability and reproducibility were met by 76% and 44% of tests in the TN and UC models, respectively (p < 0.0001). 125 (24%) patients tested with the TN model and 38 (44%) with the UC model reported a pre-existing respiratory diagnosis (p < 0.0001). Three months after spirometry, when the ratio of forced expiratory volume in 1 s/forced vital capacity (FEV(1)/FVC) was < 0.7 and no prior COPD diagnosis was reported, nine (8%) participants had a new doctor recorded COPD diagnosis in practices with the TN model and two (8%) participants in practices with the UC model. Mislabelling of participants with a diagnosis of COPD when FEV(1)/FVC was > or = 0.7 was present in both models prior to and after spirometry. GPs valued high quality spirometry and increased testing of patients at risk of COPD in the TN model. They identified limitations, including the need for better systematic follow-up of abnormal spirometry and support with interpretation, which may explain persisting underdiagnosis of COPD in practice records. CONCLUSIONS: Although opportunistic testing by visiting trained nurses substantially increased and improved spirometry performance compared with usual care, translating increased detection of airflow obstruction into diagnosis of COPD requires further development of the model. TRIAL REGISTRATION NUMBER: Australian Clinical Trials Registry: registration No 12605000019606.

Effect of a microaerosol barrier filter on the measurement of lung function.

STUDY OBJECTIVE: A disposable barrier filter (Pall Biomedical, United Kingdom) was developed to prevent the contamination of lung function equipment in clinical use. The aims of this study were to examine its resistance characteristics and to determine the effect of the filter on clinical measurements of lung function. MEASUREMENTS: Twenty-one randomly selected patients and four normal subjects had lung function measured with and without the filter between the mouth and measuring equipment. Measurements of ventilatory function were made with a pneumotachograph (Lilly; Hoechberg, Germany), total lung capacity and airway resistance by constant volume plethysmography, and diffusing capacity for carbon monoxide by the single breath method. Resistance was determined in five unused filters over the flow range 1 to 12 L/s and at a single flow rate (12 L/s) just after a normal subject expired 20 forced vital capacity (FVC) breaths through each of them. RESULTS: The resistance (mean +/- SD) of unused filters was 0.19 +/- 0.02 cm H2O/L/s at 1 L/s and increased linearly to 0.56 +/- 0.02 cm H2O/L/s at 12 L/s. There was no significant increase in resistance after use. The addition of the filter to the breathing circuit caused statistically significant decreases in forced expiratory volume in 1 s (FEV1) (0.044 +/- 0.08 L, p = 0.014) and peak expiratory flow rate (PEFR) (0.47 +/- 0.073 L/s, p = 0.004). The filter did not affect other indices of lung function. CONCLUSION: The filter caused a statistically significant reduction in FEV1 and PEFR; however, this difference was believed not to affect the clinical utility of routine lung function testing.

The effect of physiologic and mechanical aging on the performance of peak flowmeters.

PURPOSE: To investigate the effects of physiologic and mechanical aging on peak flowmeters. MATERIALS AND METHODS: Eight each of MiniWright (MW; Clement Clark; Harlow, UK), Personal-Best (PB; HealthScan Products; Cedar Grove, NJ), Vitalograph (V; Vitalograph Ltd; Buckingham, UK), and Breath-Taker (BT; Medical Development Australia; Melbourne, Australia) peak flowmeters were assessed for accuracy and repeatability before and after aging using a computer-driven syringe to deliver peak flows from 100 to 700 L/min. Four of each type of flowmeter were physiologically aged by normal subjects performing up to six peak flows daily for 1 year. The remaining four of each flowmeter were mechanically aged using an accelerated aging device to deliver 2,000 exponential waveforms with a peak flow of 600 L/min over a period of 3 h. RESULTS: The V and BT flowmeters were linear and accurate over the range 100 to 700 L/min, while the PB overread at high flows. The MW was alinear throughout. The SD of the difference between readings before and after aging ranged from 8.6 to 40.6 L/min (mean, 9.2). Comparing the slopes of the relationship of actual against reference peak expiratory flow (PEF) showed that 16 flowmeters--5 BTs, 6 MWs, 4 PBs, and 1 V had no significant change in slope after aging. Mechanical aging caused a consistent underreading in PEF at high flow rates. Physiologic aging showed a more variable pattern both within and between flowmeter types. The MW was the most affected by physiologic aging, producing overestimates of PEF by as much as 100 L/min at 500 L/min. CONCLUSIONS: We conclude that the effects of physiologic and mechanical aging are different, and that while mechanical aging may provide a guide to the effects of aging, studies using physiologic aging would be more appropriate.

Airway distensibility in healthy and asthmatic subjects: effect of lung volume history.

Anatomic dead space (VD) is known to increase with end-inspiratory lung volume (EILV), and the gradient of the relationship has been proposed as an index of airway distensibility (DeltaVD). The aims of this study were to apply a rapid method for measuring DeltaVD and to determine whether it was affected by lung volume history. VD of 16 healthy and 16 mildly asthmatic subjects was measured at a number of known EILVs by using a tidal breathing, CO(2)-washout method. The effect of lung volume history was assessed by using three tidal breathing regimens: 1) three discrete EILVs (low/medium/high; LMH); 2) progressively decreasing EILVs from total lung capacity (TLC; TLC-RV); and 3) progressively increasing EILVs from residual volume (RV; RV-TLC). DeltaVD was lower in the asthmatic group for the LMH (25.3 +/- 2.24 vs. 21.2 +/- 1.66 ml/l, means +/- SE) and TLC-RV (24. 3 +/- 1.69 vs. 18.7 +/- 1.16 ml/l) regimens. There was a trend for a lower DeltaVD in the asthmatic group for the RV-TLC regimen (23.3 +/- 2.19 vs. 18.8 +/- 1.68 ml/l). There was no difference in DeltaVD between groups. In conclusion, mild asthmatic subjects have stiffer airways than normal subjects, and this is not obviously affected by lung volume history.

Respiratory function in lambs after in utero treatment of lung hypoplasia by tracheal obstruction.

Tracheal obstruction (TO) stimulates growth of hypoplastic lungs in the fetus, but there is little knowledge of subsequent postnatal respiratory function. We have determined the effectiveness of TO in fetal sheep with existing lung hypoplasia in restoring postnatal respiratory function. Lung hypoplasia was induced by lung liquid drainage from 112 days of gestation to term ( approximately 148 days). We used an untreated group (ULH), a treated group (TLH) in which the trachea was obstructed for 10 days, and a control group. ULH lambs died within 4 h of birth. TLH lambs were hypoxic for the first week and were hypercapic at 2 days. Pulmonary diffusing capacity, gas volumes, and respiratory compliances were not different between control and TLH lambs. Minute ventilation was not different between the two groups; however, tidal volumes were lower and respiratory frequencies were higher in TLH lambs than in controls for 2 wk after birth. We conclude that 10 days of TO in the presence of initial lung hypoplasia prevents death at birth and returns most aspects of pulmonary function to normal by 1-2 wk after birth.

Measurement of lung diffusing capacity and functional residual capacity in lambs during the first postnatal month.

The diffusing capacity of the lung for carbon monoxide (DLCO) is an important index of lung function but is not easily measured in spontaneously breathing animals with small lung volumes. Our aim was to devise a simple rebreathing method that would allow us to make serial measurements of DLCO in spontaneously breathing lambs during their first month after birth. By adding He to the rebreathing gas mixture, we were also able to measure functional residual capacity (FRC), enabling us to normalize DLCO with respect to FRC. We have compared FRC measured by the rebreathing technique with that measured by a closed-circuit helium dilution method (FRCcc). Using the rebreathing method we found highly significant positive correlations between DLCO and body weight (r = 0.70, P < 0.001) and between FRC and body weight (r = 0.79, P < 0.001). There was no significant change in DLCO/FRC over the first postnatal month; the mean value was 8.1 +/- 0.6 mL/min/mmHg/mL. Rebreathing FRC was highly correlated with FRCcc (r = 0.88, P < 0.001), but was lower than FRCcc by about 18%. In normal lambs DLCO and FRC, but not DLCO/FRC, increased during the first month after birth, suggesting that the increase in DLCO parallels lung growth. We conclude that the modified rebreathing method is suitable for measuring DLCO in small uncooperative spontaneously breathing animals.

Infection control of lung function equipment: a practical approach.

The degree of risk of cross-infection of patients via lung function testing equipment has yet to be quantified. Based on current evidence, elaborate precautions are not justified for the majority of patients attending the laboratory, but attention to appropriate routine cleaning and disinfection protocols is important. Disinfection and sterilization can be achieved by a variety of methods, although chemical methods should be used with caution. Identification of factors increasing the susceptibility or infectivity of particular patients is important in determining appropriate precautions. Where patients are known to be infectious or are immunocompromized, additional precautions such as using a barrier filter may be appropriate. However, because of cost constraints, the routine use of barrier filters is difficult to justify based on current evidence of minimal cross-infection associated with lung function equipment. Until further studies have been conducted to quantify the degree of risk of cross-infection that lung function test equipment poses, the recommendations given in this review provide a practical approach to dealing with this problem.

An air-entrainment device for preparing precision gas mixtures.

Three low-cost venturi's built from readily available materials are described and evaluated to determine whether they can be used to prepare precision gas mixtures for the calibration of gas analysers. Using pure oxygen (O2) and nitrogen as the priming gases the venturi's generated mixtures with an O2 concentration within the range 12-53% O2. Over a two-week period, the variability was found to be less than 0.25% O2. The mixtures produced were found to vary according to the density of the priming gas, but were virtually independent of the priming flow rate. We conclude that the venturi may offer a simple and inexpensive method of preparing precision gas mixtures suitable for the calibration of gas analysers.

Cardiovascular effects of methacholine-induced airway obstruction in man.

Cardiovascular disease is the most frequent cause of death in people with chronic respiratory disease. The cause of this association has been attributed to airway obstruction leading to cardiovascular dysfunction (increased central blood pressure (BP) and aortic stiffness). However, this has never been experimentally tested. Methacholine is routinely used to stimulate airway function changes that mimic airway pathology. This study aimed to determine the cardiovascular effects of methacholine-induced airway obstruction. Fifteen healthy young adults (aged 22.9±2.5 years; 4 male; mean±S.D.) underwent a bronchial challenge test (randomized, blinded, cross-over design) in which they received nebulized methacholine inhalation in serially increasing concentrations (from 0.39 to 25 mg/ml) or saline (0.9%; control) on two separate days. Bronchoconstriction was assessed by forced expiratory volume at one second (FEV1) and cardiovascular effects by augmentation index, brachial BP, central BP, heart rate and aortic stiffness. Methacholine significantly decreased FEV1 from baseline to peak inhaled concentration compared with saline (-0.48±0.34 vs. -0.07±0.16 L; p<0.001), but there was no between-group change in augmentation index (1.6±7.0 vs. 3.7±10.2% p=0.49), brachial systolic BP (-3.3±7.6 vs. -4.7±5.7 mmHg; p=0.59), central systolic BP (-1.1±5.2 vs. -0.3±5.5 mmHg; p=0.73), heart rate (0.4±7.1 vs. -0.8±6.6 bpm; p=0.45) or aortic stiffness (0.2±1.3 vs. 0.8±1.8 m/s; p=0.20; n=12). Thus, methacholine induced airway obstruction does not acutely change brachial BP or central haemodynamics. This finding refutes the notion that airway obstruction per se leads to cardiovascular dysfunction, at least in healthy individuals in the acute setting.

Poor lung function and tonsillectomy in childhood are associated with mortality from age 18 to 44.

BACKGROUND: The aim of this analysis was to examine associations between lung health in childhood and mortality between ages 18 and 44 years in the Tasmanian Longitudinal Health Study (TAHS). METHODS: The 1961 Tasmanian birth cohort who attended school in 1968 (n=8583) were linked to the Australian National Death Index (NDI) to identify deaths. Additional deaths were notified by families through a 37 year follow-up postal questionnaire. Information on lung health at age 7 years and on potential confounders was obtained from the original 1968 TAHS survey and school medical records. Cox proportional hazards modelling was used to assess determinants of mortality. RESULTS: A total of 264 (3%) deaths were identified. The principal causes of death were external injury (56.1%, n=97) and cancer (17.9%, n=31). Males were more likely than females to have died (p=<0.1). Only two (1.1%) participants had died from respiratory conditions. Having an FEV(1)<80% predicted at 7 years of age was associated with a 2-fold increased incidence of death. Tonsillectomy before age 7 years was associated with a 1.5-fold increase in mortality (p=0.05); being male with a 3.6-fold increase in mortality (p=0.0001); and repeated chest illnesses at age 7 years causing >30 days confinement in the last year, was associated with a 2.2-fold increase in mortality (p=0.03). CONCLUSIONS: Childhood lung health appears to be associated with increased mortality in adulthood, perhaps by affecting the ability to survive trauma, major illnesses and other physical stresses.

Nonpharmacological and pharmacological interventions to prevent or reduce airway remodelling.

In the present review of airway remodelling and its response to therapies, clinical observations about airway physiological abnormalities, assumed to be caused by remodelling processes, are related to what is known about the components of structural changes from airway sampling and histopathological analysis. The review focuses on three important diseases: asthma, chronic obstructive pulmonary disease and bronchiolitis obliterans syndrome (BOS), which occurs commonly after lung transplantation as a manifestation of chronic rejection. The present authors chose to use BOS as an issue, because with routine bronchoscopic surveillance after lung transplantation there has been more opportunity to directly study airway pathology longitudinally than in more everyday conditions. In addition, the present authors have reviewed animal models of induced airway remodelling, where most information is available on the potential of therapeutic intervention. Finally, the limited information that can be gained from the literature on the effects of commonly used airway medications on remodelling components is reviewed. In conclusion, the present authors have detailed some of the gaps in knowledge surrounding the potential to improve or modulate remodelling processes in human disease. The areas where it is believed urgent research needs to be focused have also been highlighted.

Airway cell and cytokine changes in early asthma deterioration after inhaled corticosteroid reduction.

BACKGROUND: Back-titration of inhaled corticosteroid (ICS) dose in well-controlled asthma patients is emphasized in clinical guidelines, but there are few published data on the airway cell and cytokine changes in relation to ICS reduction. In our study, 20 mild-to-moderate persistent (inspite of low-moderate dose ICS treatment) asthmatic subjects prospectively rendered largely asymptomatic by high-dose ICS were assessed again by clinical, physiological, and airway inflammatory indices after 4-8 weeks of reduced ICS treatment. We aimed at assessing the underlying pathological changes in relation to clinical deterioration. METHODS: Patients recorded daily symptom scores and peak expiratory flows (PEF). Spirometry and airways hyperreactivity (AHR) were measured and bronchoscopy was performed with assessment of airway biopsies (mast cells, eosinophils, neutrophils, and T lymphocytes), bronchoalveolar lavage (BAL) IL-5 and eotaxin levels and cellular profiles at the end of high-dose ICS therapy and again after ICS dose reduction. Baseline data were compared with symptomatic steroid-free asthmatics (n=42) and non-asthmatic controls (n=28). RESULTS: After ICS reduction, subjects experienced a variable but overall significant increase in symptoms and reductions in PEF and forced expiratory volume in 1 s. There were no corresponding changes in AHR or airways eosinophilia. The most relevant pathogenic changes were increased CD4(+)/CD8(+) T cell ratio, and decreased sICAM-1 and CD18 macrophage staining (potentially indicating ligand binding). However, there was no relationship between the spectrum of clinical deterioration and the changes in cellular profiles or BAL cytokines. CONCLUSIONS: These data suggest that clinical markers remain the most sensitive measures of early deterioration in asthma during back-titration of ICS, occurring at a time when AHR and conventional indices of asthmatic airway inflammation appear unchanged. These findings have major relevance to management and to how back-titration of ICS therapy is monitored.

How have we been managing chronic obstructive pulmonary disease in Australia?

AIM: Although chronic obstructive pulmonary disease (COPD) is a main cause of disability, hospital admissions and premature deaths in Australia, little is known about the community management of COPD in relation to recently published guidelines. The aim of the article was to report on COPD management in a community based cohort. METHODS: A random sample of adults aged between 45 and 70 years drawn from the electoral roll participated in the study. They completed a detailed respiratory questionnaire, spirometry, methacholine challenge and measurement of transfer factor. COPD was defined according to the Global initiative for Chronic Obstructive Lung Disease (GOLD) criteria. Current asthma was defined as wheeze during the last 12 months together with bronchial hyperreactivity. Subjects were classified as either COPD-only, asthma-only or both asthma and COPD. RESULTS: Of 1224 subjects completing spirometry, 39 (3.5%) met the GOLD criteria for stage 2 or 3 COPD, asthma-only was found in 99 (8.9%) subjects and 40 (3.6%) subjects had both asthma and COPD. The COPD-only group was significantly older than the other two groups. More than 40% of subjects with COPD did not have a diagnosis of COPD from their doctors. Only 48.7% of subjects with COPD had ever been prescribed medication for their breathing. More than two-thirds of all subjects had seen a doctor for breathing problems, but very few had seen a general practitioner in the last 12 months and even fewer had respiratory function tests. CONCLUSIONS: Most subjects with COPD are being undertreated. Diagnosis, monitoring and referral systems should be improved. Preventive activities such as influenza vaccination and smoking cessation should be intensified.

Inter-relationships between airway inflammation, reticular basement membrane thickening and bronchial hyper-reactivity to methacholine in asthma; a systematic bronchoalveolar lavage and airway biopsy analysis.

BACKGROUND: Asthma is accepted as a disease characterized by airway inflammation, with evidence that airway structural changes, or 'remodelling' occurs. There are few studies relating airway physiology, inflammation and remodelling, however. We have carried out a study of inter-relationships between airway inflammation, airway remodelling, reticular basement membrane (RBM) thickening, and bronchial hyper-reactivity (BHR), before and after high-dose inhaled corticosteroid (fluticasone propionate 750 microg b.d.), in a group of relatively mild but symptomatic, steroid naïve asthma patients. METHODS: Double-blind, randomized, placebo-controlled, parallel group study of inhaled corticosteroid (ICS) in 35 asthmatics, with bronchoalveolar lavage (BAL) and airway endobronchial biopsy (EBB) for inflammatory cell profiles and EBB for airway remodelling carried out at baseline, 3 and 12 months. RESULTS: At baseline RBM thickening was related to BAL mast cells and EBB eosinophil counts. In turn baseline log EBB EG2 eosinophil count, log%BAL epithelial cells and log RBM thickness explained 55% of the variability in BHR. CONCLUSION: We provide new information that airway inflammation, remodelling, and BHR in asthma are inter-related and improved by ICS therapy. Our data potentially support the need for early and long-term intervention with ICS even in relatively mild asthmatics, and the need to further assess the potential merit of longitudinal BHR testing in management of some patients, as this may reflect both airway inflammation and remodelling.

Biological dust exposure in the workplace is a risk factor for chronic obstructive pulmonary disease.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality. Although the main risk factor is smoking, 15-19% of COPD even in smokers has been attributed to occupational exposures. The aim of this study was to investigate the association between occupational exposure and risk of COPD. METHODS: Participants were part of a cross sectional study of risk factors for COPD. A total of 1232 completed a detailed respiratory questionnaire, spirometric testing and measurement of gas transfer. Job histories were coded according to the International Standard Classification of Occupations. These codes were then used to establish occupational exposures using the ALOHA job exposure matrix. RESULTS: The prevalence of emphysema was 2.4%, chronic obstructive bronchitis 1.8%, and COPD 3.4%. Subjects ever exposed to biological dusts had an increased risk of chronic obstructive bronchitis (OR 3.19; 95% CI 1.27 to 7.97), emphysema (OR 3.18; 95% CI 1.41 to 7.13), and COPD (OR 2.70, 95% CI 1.39 to 5.23). These risks were higher in women than in men. For biological dust, the risk of emphysema and COPD was also significantly increased in both the duration of exposure categories, again in women but not in men. No significant increased risks for COPD were found for mineral dust (OR 1.13; 95% CI 0.57 to 2.27) or gases/fumes (OR 1.63; 95% CI 0.83 to 3.22). CONCLUSION: In this general population sample of adults, occupational exposures to biological dusts were associated with an increased risk of COPD which was higher in women. Preventive strategies should be aimed at reducing exposure to these agents in the workplace.