Association between lung function and dyspnoea and its variation in the multinational Burden of Obstructive Lung Disease (BOLD) study

BACKGROUND

Dyspnoea is a common symptom of respiratory disease. However, data on its prevalence in general populations and its association with lung function are limited and are mainly from high-income countries. The aims of this study were to estimate the prevalence of dyspnoea across several world regions, and to investigate the association of dyspnoea with lung function.

METHODS

Dyspnoea was assessed, and lung function measured in 25,806 adult participants of the multinational Burden of Obstructive Lung Disease study. Dyspnoea was defined as ≥2 on the modified Medical Research Council (mMRC) dyspnoea scale. The prevalence of dyspnoea was estimated for each of the study sites and compared across countries and world regions. Multivariable logistic regression was used to assess the association of dyspnoea with lung function in each site. Results were then pooled using random-effects meta-analysis.

RESULTS

The prevalence of dyspnoea varied widely across sites without a clear geographical pattern. The mean prevalence of dyspnoea was 13.7 % (SD=8.2 %), ranging from 0 % in Mysore (India) to 28.8 % in Nampicuan-Talugtug (Philippines). Dyspnoea was strongly associated with both spirometry restriction (FVC

CONCLUSION

The prevalence of dyspnoea varies substantially across the world and is strongly associated with lung function impairment. Using the mMRC scale in epidemiological research should be discussed.

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Key Words

• Breathlessness
• Dyspnoea
• Lung function
• Spirometry

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Affiliation(s)

A Müller Ludwig Boltzmann Institute for Lung Health, Vienna, Austria; Care and Public Health Research Institute, Faculty of Health Medicine and Life Sciences, Maastricht University, Maastricht, the Netherlands.
E F Wouters Ludwig Boltzmann Institute for Lung Health, Vienna, Austria; Sigmund Freud University, Faculty of Medicine, Vienna, Austria; Department of Respiratory Medicine, Maastricht University Medical Center, Maastricht, the Netherlands
P Koul Department of Pulmonary Medicine, Sheri Kashmir Institute of Medical Sciences, Srinagar, India
T Welte Department of Respiratory Medicine/Infectious Disease, Member of the German Centre for Lung Research, Hannover School of Medicine, Hannover, Germany
I Harrabi Faculté de Médecine, Sousse, Tunisia
A Rashid RCSI and UCD Malaysia Campus, Penang, Malaysia
L C Loh RUMC, Penang, Malaysia
M Al Ghobain King Abdullah International Medical Research Center, King Saud ben Abdulaziz University for Health Science, Riyadh, Saudi Arabia
A Elsony The Epidemiological Laboratory, Khartoum, Sudan
R Ahmed The Epidemiological Laboratory, Khartoum, Sudan
J Potts National Heart and Lung Institute, Imperial College London, London, UK
K Mortimer University of Cambridge, Cambridge, UK; Liverpool University Hospitals NHS Foundation Trust, Liverpool, UK
F Rodrigues Pulmonology Department, Lisbon North Hospital Centre, Lisbon, Portugal; Institute of Environmental Health, Associate Laboratory TERRA, Lisbon Medical School, Lisbon University, Lisbon, Portugal
S N Paraguas Philippine College of Chest Physicians, Manila, Philippines
S Juvekar KEM Hospital Research Centre, Pune, India
D Agarwal KEM Hospital Research Centre, Pune, India
D Obaseki Department of Medicine, Obafemi Awolowo University, Nigeria; Faculty of Medicine, University of British Columbia, Canada
T Gislason Faculty of Medicine, University of Iceland, Reykjavik, Iceland; Department of Sleep, Landspitali - The National University Hospital of Iceland, Reykjavik, Iceland
T Seemungal Faculty of Medical Sciences, University of West Indies, St Augustine, Trinidad and Tobago
A A Nafees Aga Khan University, Karachi, Pakistan
C Jenkins Woolcock Institute of Medical Research, Sydney, Australia
H B Dias Escola Superior de Tecnologia da Saúde de Lisboa, Politecnico de Lisboa, Lisbon, Portugal
F M E Franssen Department of Respiratory Medicine, Maastricht University Medical Center, Maastricht, the Netherlands; Department of Research and Development, Ciro, Horn, the Netherlands
M Studnicka Department of Pulmonary Medicine, Paracelsus Medical University, Salzburg, Austria
C Janson Department of Medical Sciences: Respiratory, Allergy and Sleep Research, Uppsala University, Uppsala, Sweden
H H Cherkaski Faculty of Medicine, University Badji Mokhtar, Annaba, Algeria
M El Biaze Department of Respiratory Medicine, Faculty of Medicine, Mohammed Ben Abdellah University, Fes, Morocco
P A Mahesh Department of Respiratory Medicine, JSS Medical College and Hospital, Mysore, Karnataka, India
J Cardoso Pulmonology Department, Centro Hospitalar Universitário de Lisboa Central, Lisboa, Portugal; NOVA Medical School, Nova University Lisbon, Lisboa, Portugal
P Burney National Heart and Lung Institute, Imperial College London, London, UK
S Hartl Ludwig Boltzmann Institute for Lung Health, Vienna, Austria; Sigmund Freud University, Faculty of Medicine, Vienna, Austria
D J A Janssen Care and Public Health Research Institute, Faculty of Health Medicine and Life Sciences, Maastricht University, Maastricht, the Netherlands; Department of Research and Development, Ciro, Horn, the Netherlands
A F S Amaral National Heart and Lung Institute, Imperial College London, London, UK; NIHR Imperial Biomedical Research Centre, London, UK

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0053 Effect of Changes in Intracellular Adhesion Molecule-1 on Measures of Sleepiness and 24-hour Ambulatory Blood Pressure After 4 Months of Continuous Positive Airway Pressure

Introduction

Previous studies have shown that continuous positive airway pressure (CPAP) therapy of adults with obstructive sleep apnea (OSA) reduces circulating levels of intercellular adhesion molecule 1 (ICAM-1). ICAM-1 levels may affect daytime sleepiness and elevated blood pressure associated with OSA. Our goals were to explore associations between changes in ICAM-1 and objective and subjective measures of sleepiness, as well as 24-hour ambulatory blood pressure monitor (ABPM) parameters in adults with OSA following 4 months of CPAP treatment.

Methods

We identified 140 adults with newly diagnosed OSA in the Penn Icelandic Sleep Apnea (PISA) Study, with a mean (±SD) body mass index (BMI) of 31.5±4.2 kg/m2 and apnea-hypopnea index (AHI) of 36.8±15.3 events/hour; 83.3% were males. Plasma ICAM-1 levels, 24-hour ABPM, Epworth Sleepiness Scale (ESS), and Psychomotor Vigilance Task (PVT) measures were obtained at baseline and after 4 months of CPAP treatment. Associations between changes in natural log ICAM-1 and both sleepiness and 24-hour mean arterial blood pressure (MAP) were assessed using multivariate regression models, controlling for a priori baseline covariates of age, sex, BMI, race, site, smoking status, physical activity, use of anti-hypertensive medications, AHI and hours/night of CPAP usage.

Results

Overall, there was no significant change in ICAM-1 from baseline to follow-up among all participants after 4 months (0.027 ng/ml, p=0.52). There were no statistically significant associations between the change in ICAM-1 and change in sleepiness measures (all p>0.05) or 24-hour MAP (1.124 mm Hg, p=0.07). A nominal association between increased ICAM-1 and increased daytime MAP after 4 months was observed (1.39 mm Hg, p=0.033), although this result was not significant after correction for multiple comparisons.

Conclusion

Our results do not support changes in ICAM-1 as the biological pathway linking changes in sleepiness or ABPM following CPAP treatment of adults with OSA.

Support

P01-HL094307 (NHLBI, PI: Pack AI)

Determinants of fractional exhaled nitric oxide in healthy men and women from the European Community Respiratory Health Survey III

INTRODUCTION

The fractional exhaled nitric oxide (F_E NO) is a marker for type 2 inflammation used in diagnostics and management of asthma. In order to use F_E NO as a reliable biomarker, it is important to investigate factors that influence F_E NO in healthy individuals. Men have higher levels of F_E NO than women, but it is unclear whether determinants of F_E NO differ by sex.

OBJECTIVE

To identify determinants of F_E NO in men and women without lung diseases.

METHOD

Fractional exhaled nitric oxide was validly measured in 3881 healthy subjects that had answered the main questionnaire of the European Community Respiratory Health Survey III without airways or lung disease.

RESULTS

Exhaled NO levels were 21.3% higher in men compared with women P < 0.001. Being in the upper age quartile (60.3-67.6 years), men had 19.2 ppb (95% CI: 18.3, 20.2) higher F_E NO than subjects in the lowest age quartile (39.7-48.3 years) P = 0.02. Women in the two highest age quartiles (54.6-60.2 and 60.3-67.6 years) had 15.4 ppb (14.7, 16.2), P = 0.03 and 16.4 ppb (15.6, 17.1), P = <0.001 higher F_E NO, compared with the lowest age quartile. Height was related to 8% higher F_E NO level in men (P < 0.001) and 5% higher F_E NO levels in women (P = 0.008). Men who smoked had 37% lower F_E NO levels and women had 30% lower levels compared with never-smokers (P < 0.001 for both). Men and women sensitized to both grass and perennial allergens had higher F_E NO levels compared with non-sensitized subjects 26% and 29%, P < 0.001 for both.

CONCLUSION AND CLINICAL RELEVANCE

Fractional exhaled nitric oxide levels were higher in men than women. Similar effects of current smoking, height, and IgE sensitization were found in both sexes. F_E NO started increasing at lower age in women than in men, suggesting that interpretation of F_E NO levels in adults aged over 50 years should take into account age and sex.

Microbial characteristics in homes of asthmatic and non-asthmatic adults in the ECRHS cohort

Microbial exposures in homes of asthmatic adults have been rarely investigated; specificities and implications for respiratory health are not well understood. The objectives of this study were to investigate associations of microbial levels with asthma status, asthma symptoms, bronchial hyperresponsiveness (BHR), and atopy. Mattress dust samples of 199 asthmatics and 198 control subjects from 7 European countries participating in the European Community Respiratory Health Survey II study were analyzed for fungal and bacterial cell wall components and individual taxa. We observed trends for protective associations of higher levels of mostly bacterial markers. Increased levels of muramic acid, a cell wall component predominant in Gram-positive bacteria, tended to be inversely associated with asthma (OR's for different quartiles: II 0.71 [0.39-1.30], III 0.44 [0.23-0.82], and IV 0.60 [0.31-1.18] P for trend .07) and with asthma score (P for trend .06) and with atopy (P for trend .02). These associations were more pronounced in northern Europe. This study among adults across Europe supports a potential protective effect of Gram-positive bacteria in mattress dust and points out that this may be more pronounced in areas where microbial exposure levels are generally lower.

The effects of growing up on a farm on adult lung function and allergic phenotypes: an international population-based study

RATIONALE

Evidence has suggested that exposure to environmental or microbial biodiversity in early life may impact subsequent lung function and allergic disease risk.

OBJECTIVES

To investigate the influence of childhood living environment and biodiversity indicators on atopy, asthma and lung function in adulthood.

METHODS AND MEASUREMENTS

The European Community Respiratory Health Survey II investigated ∼10 201 participants aged 26-54 years from 14 countries, including participants' place of upbringing (farm, rural environment or inner city) before age 5 years. A 'biodiversity score' was created based on childhood exposure to cats, dogs, day care, bedroom sharing and older siblings. Associations with lung function, bronchial hyper-responsiveness (BHR), allergic sensitisation, asthma and rhinitis were analysed.

MAIN RESULTS

As compared with a city upbringing, those with early-life farm exposure had less atopic sensitisation (adjusted OR 0.46, 95% CI 0.37 to 0.58), atopic BHR (0.54 (0.35 to 0.83)), atopic asthma (0.47 (0.28 to 0.81)) and atopic rhinitis (0.43 (0.32 to 0.57)), but not non-atopic outcomes. Less pronounced protective effects were observed for rural environment exposures. Women with a farm upbringing had higher FEV₁ (adjusted difference 110 mL (64 to 157)), independent of sensitisation and asthma. In an inner city environment, a higher biodiversity score was related to less allergic sensitisation.

CONCLUSIONS

This is the first study to report beneficial effects of growing up on a farm on adult FEV₁. Our study confirmed the beneficial effects of early farm life on sensitisation, asthma and rhinitis, and found a similar association for BHR. In persons with an urban upbringing, a higher biodiversity score predicted less allergic sensitisation, but to a lesser magnitude than a childhood farm environment.

Computed Tomography of the Oropharynx in Obstructive Sleep Apnea

Uvulopalatopharyngoplasty (UPPP) is currently the preferred method for treatment of the obstructive sleep apnea syndrome (OSAS). However, only 50 per cent of the patients operated upon are cured by this surgical procedure, and there is a demand for better and more objective selection criteria. Computed tomography (CT) of the oropharynx was obtained in 32 consecutive adult patients with proven OSAS. An additional 15 patients with the same complaints, but without objective evidence of OSAS, were used as a control group, together with 20 normal subjects. The axial widths of the tongue and the genioglossus and hyoglossus muscles were measured by CT. Both the tongue and genioglossus widths were significantly larger in the OSAS patients than in the two control groups (p<0.001). The increased tongue width will cause encroachment of the oropharyngeal airway below the level of the soft palate. Thus, CT can be used to measure the tongue size in order to evaluate its predictive value for the outcome of the UPPP procedure.

A rare missense mutation in CHRNA4 associates with smoking behavior and its consequences

Using Icelandic whole-genome sequence data and an imputation approach we searched for rare sequence variants in CHRNA4 and tested them for association with nicotine dependence. We show that carriers of a rare missense variant (allele frequency=0.24%) within CHRNA4, encoding an R336C substitution, have greater risk of nicotine addiction than non-carriers as assessed by the Fagerstrom Test for Nicotine Dependence (P=1.2 × 10(-4)). The variant also confers risk of several serious smoking-related diseases previously shown to be associated with the D398N substitution in CHRNA5. We observed odds ratios (ORs) of 1.7-2.3 for lung cancer (LC; P=4.0 × 10(-4)), chronic obstructive pulmonary disease (COPD; P=9.3 × 10(-4)), peripheral artery disease (PAD; P=0.090) and abdominal aortic aneurysms (AAAs; P=0.12), and the variant associates strongly with the early-onset forms of LC (OR=4.49, P=2.2 × 10(-4)), COPD (OR=3.22, P=2.9 × 10(-4)), PAD (OR=3.47, P=9.2 × 10(-3)) and AAA (OR=6.44, P=6.3 × 10(-3)). Joint analysis of the four smoking-related diseases reveals significant association (P=6.8 × 10(-5)), particularly for early-onset cases (P=2.1 × 10(-7)). Our results are in agreement with functional studies showing that the human α4β2 isoform of the channel containing R336C has less sensitivity for its agonists than the wild-type form following nicotine incubation.

Nocturnal GERD - a risk factor for rhinitis/rhinosinusitis: the RHINE study

BACKGROUND

It has been suggested that gastroesophageal reflux disease (GERD) is a risk factor for developing rhinitis/rhinosinusitis, but data are lacking. This is a prospective 10-year follow-up study of a large multicenter cohort from Northern Europe, evaluating the relationship between nocturnal GERD and noninfectious rhinitis (NIR).

METHODS

The study comprised 5417 subjects born between 1945 and 1973, who answered a questionnaire in 1999-2001 and again in 2010-2012. Noninfectious rhinitis was defined as having nasal obstruction, secretion, and/or sneezing without having the common cold. Odds ratios for developing NIR in relation to age, gender, BMI, smoking, asthma, and nocturnal GERD were calculated.

RESULTS

During the 10-year observation period, 1034 subjects (19.1%) developed NIR. Subjects reporting nocturnal gastroesophageal reflux in both 1999 and 2010 had more NIR in 2010 (2.8% vs 1.2%, P < 0.001). There was a significant dose-response relationship between the number of reflux episodes/week in 1999 and the risk of having NIR in 2010, P = 0.02. In the multiple regression adjusted for age, gender, BMI, tobacco smoke, and asthma, those with nocturnal GERD in 1999 (≥3 episodes of nocturnal gastroesophageal reflux symptoms per week) had an OR of 1.6 (95% CI 1.0-2.5, P = 0.03) to develop NIR in 2010. Smoking was associated both with an increased risk of developing NIR (30.7% vs 24.0%, P < 0.001) and with the development of nocturnal GERD.

CONCLUSION

This large, population-based, 10-year study indicates that nocturnal GERD was a risk factor for noninfectious rhinitis/rhinosinusitis. GERD should therefore be considered in patients with rhinitis of known and unknown origin.

Onset of mucosal, dermal, and general symptoms in relation to biomarkers and exposures in the dwelling: a cohort study from 1992 to 2002

We examined the associations between biomarkers of allergy and inflammation, indoor environment in dwellings, and incidence and remission of symptoms included in the sick building syndrome (SBS) and changes in the home environment of 452 adults who were followed from 1992 to 2002 within the Uppsala part of the European Community Respiratory Health Survey (ECRHS). The 10-year incidence (onset) of general, mucosal, and dermal symptoms was 8.5%, 12.7%, and 6.8%, respectively. Dampness or indoor molds at baseline was a predictor of incidence of general (relative risk [RR] = 1.98), mucosal (RR = 2.28), and dermal symptoms (RR = 1.91). Women had higher incidence of general (RR = 1.74) and mucosal symptoms (RR = 1.71). Indoor painting increased the incidence of general symptoms (RR = 1.62). Bronchial responsiveness (BR), eosinophil counts in blood, total IgE and eosinophilic cationic protein (ECP) in serum at baseline were predictors of incidence of SBS. At follow-up, BR, total IgE, and C-reactive protein (CRP ) were associated with increased incidence of SBS. Moreover, subjects with doctor-diagnosed asthma at baseline had a higher incidence of general (RR = 1.65) and mucosal symptoms (RR = 1.97). In conclusion, female gender, dampness or indoor molds, indoor painting, and biomarkers of allergy and inflammation were associated with a higher incidence of SBS symptoms, in particular mucosal symptoms.

PRACTICAL IMPLICATIONS

The focus in Sweden on indoor environment issues over the last few decades has resulted in improvements in dwellings, and reduced tobacco smoking, which could be beneficial for public health. Reducing dampness and molds in the dwelling place is another important way of reducing occurrence of SBS symptoms in the general adult population. The association between the incidence of SBS symptoms and clinical biomarkers of allergy and inflammation suggests a common etiology between inflammatory diseases, including asthma, rhinitis, and SBS. Lastly, good agreement between self-reported and clinically diagnosed atopy indicates that questionnaire data on atopy can be used in epidemiological studies.

Risk factors of new-onset asthma in adults: a population-based international cohort study

BACKGROUND

The occurrence of new-onset asthma during adulthood is common, but there is insufficient understanding of its determinants including the role of atopy.

OBJECTIVE

To assess the risk factors for the development of new-onset asthma in middle-aged adults and to compare them according to atopy.

METHODS

A longitudinal analysis of 9175 young adults who participated in two surveys of the European Community Respiratory Health Survey (ECRHS) conducted 9 years apart.

FINDINGS

We observed 179 cases of new-onset asthma among 4588 participants who were free of asthma and reported at the beginning of the follow-up that they had never had asthma (4.5 per 1000 person-years). In a logistic regression, the following risk factors were found to increase the risk of new-onset asthma: female gender (OR: 1.97; 95% confidence interval (CI): 1.38, 2.81), bronchial hyperresponsiveness (3.25; 2.19, 4.83), atopy (1.55; 1.08, 2.21), FEV(1) < 100 % predicted (1.87; 1.34, 2.62), nasal allergy (1.98;1.39,2.84) and maternal asthma (1.91; 1.13; 3.21). Obesity, respiratory infections in early life and high-risk occupations increased the risk of new-onset asthma although we had limited power to confirm their role. Among the atopics, total IgE and sensitization to cat were independently related to the risk of new-onset asthma. The proportion of new-onset asthma attributable to atopy varied from 12% to 21%.

CONCLUSION

Adults reporting that they had never had asthma were at a substantial risk of new-onset asthma as a result of multiple independent risk factors including lung function. Atopy explains a small proportion of new-onset adult asthma.

What can we learn about asthma and allergy from the follow-up of the RHINE and the ECRHS studies?

OBJECT

The international population-based studies RHINE and ECRHS have provided new insight in the epidemiology and management of asthma, allergy and rhinitis in young adults. The aim of the present review is to focus on longitudinal results with regard incidence and net change of asthma and asthma-like symptoms, risk factors and management of asthma, with special reference to the Nordic-Baltic countries.

RESULTS

Asthma and rhinitis are common conditions that are important in a public health perspective. There are gender differences in incidence and remission. A socio-economic gradient that non-atopic asthma is more strongly related to poverty seems to have developed in the last decade. These findings will challenge our welfare states in the future. In addition, occupational, as well as indoor and outdoor environmental exposures, influenced the onset of asthma. The population-attributable risk for adult asthma because of occupational exposures is equivalent to an incidence of new-onset asthma of 250-300 cases per million per year. Genetic factors, allergic sensitisation, gastro-oesophageal reflux, habitual snoring, diet and other factors may also contribute to the onset of asthma and rhinitis. Even though management of asthma has improved, there are still great variations throughout Europe. These findings highlight the key role doctors and nurses play in educating and reviewing management of patients.

Snoring and systemic hypertension--an epidemiological study

The prevalence of snoring, overweight and systemic hypertension was estimated in a random sample of 4,064 Swedish men, aged 30-69 years. Of the responders, 15.5% complained of habitual snoring and 29.6% of occasional snoring. Although there was an age-related increase in the prevalence of snoring up to 60 years, habitual snoring was found to be mainly related to body mass index (BMI) (p less than 0.0001) but not to age. Altogether 299 men (9.3%) reported hypertension, 21.5% of whom were habitual snorers, compared with 14.9% of the non-hypertensives (p less than 0.01). The hypertensives were also more often overweight. Logistic multiple regression analyses showed that among subjects 40-49 years old there was an average increase in the predicted prevalence of hypertension from 6.5% among non-snorers to 10.5% of habitual snorers in the same weight group. For the whole study population, however, the increase was mainly dependent on age and BMI. Thus, the importance of habitual snoring for the prevalence of hypertension differs in various age groups.

Present and future costs of COPD in Iceland and Norway: results from the BOLD study

The Burden of Obstructive Lung Disease (BOLD) initiative provides standardised estimates of the burden of chronic obstructive pulmonary disease (COPD) worldwide. We estimate the current and future economic burden of COPD in Reykjavik, Iceland and Bergen, Norway using data from the BOLD initiative. Data on utilisation of healthcare resources were gathered from the BOLD survey, existing literature and unit costs from national sources. Economic data were applied to a Markov model using transition probabilities derived from Framingham data. Sensitivity analyses were conducted varying unit costs, utilisation and prevalence of disease. The cost of COPD was 478 euro per patient per yr in Iceland and 284 euro per patient per yr in Norway. The estimated cumulative costs of COPD for the population aged > or = 40 yrs, were 130 million euro and 1,539 million euro for the following 10 yrs in Iceland and Norway, respectively. Costs of COPD accounted for 1.2 and 0.7% of healthcare budgets in Iceland and Norway, respectively. Sensitivity analyses showed estimates were most sensitive to changes in exacerbation frequency. COPD has a significant economic burden in both Iceland and Norway and will grow in the future. Interventions aimed at avoiding exacerbations will have the most impact on costs of COPD over the next 20 yrs.

Underestimation of airflow obstruction among young adults using FEV1/FVC <70% as a fixed cut-off: a longitudinal evaluation of clinical and functional outcomes

BACKGROUND

Early detection of airflow obstruction is particularly important among young adults because they are more likely to benefit from intervention. Using the forced expiratory volume in 1 s (FEV(1)) to forced vital capacity (FVC) (FEV(1)/FVC) <70% fixed ratio, airflow obstruction may be underdiagnosed. The lower limit of normal (LLN), which is statistically defined by the lower fifth percentile of a reference population, is physiologically appropriate but it still needs a clinical validation.

METHODS

To evaluate the characteristics and longitudinal outcomes of subjects misidentified as normal by the fixed ratio with respect to the LLN, 6249 participants (aged 20-44 years) in the European Community Respiratory Health Survey were examined and divided into three groups (absence of airflow obstruction by the LLN and the fixed ratio; presence of airflow obstruction only by the LLN; presence of airflow obstruction by the two criteria) for 1991-1993. LLN equations were obtained from normal non-smoking participants. A set of clinical and functional outcomes was evaluated in 1999-2002.

RESULTS

The misidentified subjects were 318 (5.1%); only 45.6% of the subjects with airflow obstruction by the LLN were also identified by the fixed cut-off. At baseline, FEV(1) (107%, 97%, 85%) progressively decreased and bronchial hyperresponsiveness (slope 7.84, 6.32, 5.57) progressively increased across the three groups. During follow-up, misidentified subjects had a significantly higher risk of developing chronic obstructive pulmonary disease and a significantly higher use of health resources (medicines, emergency department visits/hospital admissions) because of breathing problems than subjects without airflow obstruction (p<0.001).

CONCLUSIONS

Our findings show the importance of using statistically derived spirometric criteria to identify airflow obstruction.

Changes in active and passive smoking in the European Community Respiratory Health Survey

The aim of the present investigation was to study changes and determinants for changes in active and passive smoking. The present study included 9,053 adults from 14 countries that participated in the European Community Respiratory Health Survey II. The mean follow-up period was 8.8 yrs. Change in the prevalence of active and passive smoking was expressed as absolute net change (95% confidence interval) standardised to a 10-yr period. Determinants of change were analysed and the results expressed as adjusted hazard risk ratio (HRR) or odds ratio (OR). The prevalence of active smoking declined by 5.9% (5.1-6.8) and exposure to passive smoking in nonsmokers declined by 18.4% (16.8-20.0). Subjects with a lower educational level (HRR: 0.73 (0.54-0.98) and subjects living with a smoker (HRR: 0.45 (0.34-0.59)) or with workplace smoking (HRR: 0.69 (0.50-0.95)) were less likely to quit. Low socio-economic groups were more likely to become exposed (OR: 2.21 (1.61-3.03)) and less likely to cease being exposed to passive smoking (OR: 0.48 (0.37-0.61)). In conclusion, the quitting rate was lower and the risk of exposure to passive smoking higher among subjects with lower socio-economic status. Exposure to other peoples smoking decreased quitting rates and increased the risk of starting to smoke.

Optimum expression of adult lung function based on all-cause mortality: results from the Reykjavik study

A variety of reference curves are used to derive predicted values for adult lung function, even within ethnically similar populations. Alternatives to percentage predicted value are sometimes used to allow for height in research. Strength of association with total mortality can be used to choose the optimal expression, between forced expiratory volume in 1s (FEV(1)) divided by height(2), FEV(1)/height(3), FEV(1)% predicted and difference from predicted. Data from the Reykjavik Study cohort, 1976-2002, included 5544 men and 8062 women randomly selected from the population. Total mortality was analysed by Cox proportional hazards regression in relation to each height-adjusted measure, allowing for age group, period of recruitment and body mass index, and smoking before or at baseline. FEV(1)/height(2) and FEV(1)/height(3) had stronger associations with mortality than FEV(1)% predicted and difference from predicted in men and in women. There were similar findings for forced vital capacity (FVC) in non-smokers and in women. FEV(1)/height(2) was slightly better predictive than FEV(1)/height(3) in men, but distributions of FEV(1)/height(3) in men and women were closer than those of FEV(1)/height(2). Clinical practise and epidemiological research would benefit from agreement on how to adjust lung function for height. Replication of these analyses in other cohort studies would inform the choice between FEV(1)/height(2) and FEV(1)/height(3).

Chronic bronchitis and urban air pollution in an international study

OBJECTIVES

The chronic effects of urban air pollution are not well known. The authors' aim was to investigate the association between the prevalence and new onset of chronic bronchitis and urban air pollution.

METHODS

Subjects from the general population randomly selected for the European Community Respiratory Health Survey (ECRHS I) during 1991-93 in 21 centres in 10 countries were followed up from the years 2000 to 2002 (n = 3232 males and 3592 females; average response rate = 65.3%). PM2.5 and elements, with the same equipment at centre level, and home outdoor NO2 in 1634 individuals were measured. Hierarchical models were used.

RESULTS

The prevalence and new onset of chronic phlegm during follow up were 6.9% and 4.5%, respectively, 5.3% in males and 3.5% in females. Smoking, rhinitis, poor education, and low social class were associated with (prevalence and new onset of) chronic phlegm in both genders, and occupational exposures in males and traffic intensity (adjusted odds ratio for constant traffic, OR = 1.86; 95% CI 1.24 to 2.77) as well as home outdoor NO2 (OR > 50 microg/m3v < 20 microg3 = 2.71; 95% CI 1.03 to 7.16) among females. PM2.5 and S content at centre level did not show any association with prevalence or new onset of chronic phlegm. Similar results were obtained with chronic productive cough.

CONCLUSION

Individual markers of traffic at household level such as reported intensity and outdoor NO2 were risk factors for chronic bronchitis among females.

The association between birth size and atopy in young North-European adults

BACKGROUND

There is evidence that atopic disorders may begin in intra-uterine life; however, studies of birth characteristics and atopy show conflicting results.

METHODS

We wanted to investigate the association of birth weight and head circumference with serum total or specific IgE, allergic rhinitis or eczema while addressing the influence of demographic and geographical factors. In this historic prospective cohort study, data were collected from birth records for 1683 men and women born in 1947-1973, from six Nordic-Baltic populations participating in the European Community Respiratory Health Survey. Blood tests for the measurement of serum total and specific IgE were available for 1494 subjects. In multiple regression analyses, adjustments were made for birth length, gender, age, study centre, adult body mass index, level of education, parental and adult smoking. RESULTS There was no association of birth weight (n=1230) and head circumference (n=285) with serum total IgE, specific IgE antibodies, allergic rhinitis or eczema. There were neither significant interactions by gender or age, nor heterogeneity between the study centres in the analyses of birth weight and adult atopy.

CONCLUSION

Birth size was not associated with atopy among adults in this large Nordic-Baltic population study.

Hormone replacement therapy, body mass index and asthma in perimenopausal women: a cross sectional survey

BACKGROUND

Hormone replacement therapy (HRT) and obesity both appear to increase the risk of asthma. A study was undertaken to investigate the association of HRT with asthma and hay fever in a population of perimenopausal women, focusing on a possible interaction with body mass index (BMI).

METHODS

A postal questionnaire was sent to population based samples in Denmark, Estonia, Iceland, Norway, and Sweden in 1999-2001, and 8588 women aged 25-54 years responded (77%). Pregnant women, women using oral contraceptives, and women <46 years were excluded. Analyses included 2206 women aged 46-54 years of which 884 were menopausal and 540 used HRT. Stratified analyses by BMI in tertiles were performed.

RESULTS

HRT was associated with an increased risk for asthma (OR 1.57 (95% CI 1.07 to 2.30)), wheeze (OR 1.60 (95% CI 1.22 to 2.10)), and hay fever (OR 1.48 (95% CI 1.15 to 1.90)). The associations with asthma and wheeze were significantly stronger among women with BMI in the lower tertile (asthma OR 2.41 (95% CI 1.21 to 4.77); wheeze OR 2.04 (95% CI 1.23 to 3.36)) than in heavier women (asthma: p(interaction) = 0.030; wheeze: p(interaction) = 0.042). Increasing BMI was associated with more asthma (OR 1.08 (95% CI 1.05 to 1.12) per kg/m2). This effect was only found in women not taking HRT (OR 1.10 (95% CI 1.05 to 1.14) per kg/m2); no such association was detected in HRT users (OR 1.00 (95% CI 0.92 to 1.08) per kg/m2) (p(interaction) = 0.046). Menopause was not significantly associated with asthma, wheeze, or hay fever.

CONCLUSIONS

In perimenopausal women there is an interaction between HRT and BMI in the effects on asthma. Lean women who were HRT users had as high a risk for asthma as overweight women not taking HRT. It is suggested that HRT and overweight increase the risk of asthma through partly common pathways.

Risk factors for rehospitalisation in COPD: role of health status, anxiety and depression

The aim of the present study was to analyse the risk of rehospitalisation in patients with chronic obstructive pulmonary disease and associated risk factors. This prospective study included 416 patients from a university hospital in each of the five Nordic countries. Data included demographic information, spirometry, comorbidity and 12 month follow-up for 406 patients. The hospital anxiety and depression scale and St. George's Respiratory Questionnaire (SGRQ) were applied to all patients. The number of patients that had a re-admission within 12 months was 246 (60.6%). Patients that had a re-admission had lower lung function and health status. A low forced expiratory volume in one second (FEV1) and health status were independent predictors for re-admission. Hazard ratio (HR; 95% CI) was 0.82 (0.74-0.90) per 10% increase of the predicted FEV1 and 1.06 (1.02-1.10) per 4 units increase in total SGRQ score. The risk of rehospitalisation was also increased in subjects with anxiety (HR 1.76 (1.16-2.68)) and in subjects with low health status (total SGRQ score >60 units). When comparing the different subscales in the SGRQ, the closest relation between the risk of rehospitalisation was seen with the activity scale (HR 1.07 (1.03-1.11) per 4 unit increase). In patients with low health status, anxiety is an important risk factor for rehospitalisation. This may be important for patient treatment and warrants further studies.

C reactive protein levels are increased in non-allergic but not allergic asthma: a multicentre epidemiological study

BACKGROUND

High sensitivity C reactive protein (HsCRP) is an inflammatory marker known to be related to smoking, obesity, and cardiovascular disease. A study was undertaken to determine whether HsCRP is related to respiratory symptoms, asthma, atopy, and bronchial hyperresponsiveness in population samples from three countries.

METHODS

HsCRP was measured in 1289 subjects from three centres in ECRHS II: Reykjavik, Uppsala and Tartu. The HsCRP values ranged from <0.01 mg/l to 70.0 mg/l and were divided into four equal groups (< or = 0.45, 0.46-0.96, 0.97-2.21, and >2.21 mg/l).

RESULTS

HsCRP increased with increasing body mass index (r = 0.41; p<0.0001) and was higher in smokers than in never smokers (p = 0.02). A significant relationship was found between increased HsCRP levels and respiratory symptoms such as wheeze, attacks of breathlessness after effort, and nocturnal cough (p<0.0001). The crude odds ratio (95% CI) for the probability of non-allergic asthma was 3.57 (1.83 to 6.96) for subjects in the 4th quartile compared with the 1st quartile of HsCRP. This association remained significant after adjusting for study centre, age, sex, body weight, and smoking history (OR 2.19 (95% CI 1.04 to 4.63)). No significant relationship was observed between HsCRP and allergic asthma or bronchial responsiveness.

CONCLUSIONS

Raised levels of HsCRP are significantly associated with respiratory symptoms and non-allergic asthma but not with allergic asthma.

Association of asthma and hay fever with irregular menstruation

BACKGROUND

There is some evidence that asthmatic women are more likely to have abnormal sex hormone levels. A study was undertaken to determine whether asthma and allergy were associated with irregular menstruation in a general population, and the potential role of asthma medication for this association.

METHODS

A total of 8588 women (response rate 77%) participated in an 8 year follow up postal questionnaire study of participants of the ECRHS stage I in Denmark, Estonia, Iceland, Norway, and Sweden. Only non-pregnant women not taking exogenous sex hormones were included in the analyses (n = 6137).

RESULTS

Irregular menstruation was associated with asthma (OR 1.54 (95% CI 1.11 to 2.13)), asthma symptoms (OR 1.47 (95% CI 1.16 to 1.86)), hay fever (OR 1.29 (95% CI 1.05 to 1.57)), and asthma preceded by hay fever (OR 1.95 (95% CI 1.30 to 2.96)) among women aged 26-42 years. This was also observed in women not taking asthma medication (asthma symptoms: OR 1.44 (95% CI 1.09 to 1.91); hay fever: OR 1.27 (95% CI 1.03 to 1.58); wheeze preceded by hay fever: OR 1.76 (95% CI 1.18 to 2.64)). Irregular menstruation was associated with new onset asthma in younger women (OR 1.58 (95% CI 1.03 to 2.42)) but not in women aged 42-54 years (OR 0.62 (95% CI 0.32 to 1.18)). The results were consistent across centres.

CONCLUSIONS

Younger women with asthma and allergy were more likely to have irregular menstruation. This could not be attributed to current use of asthma medication. The association could possibly be explained by common underlying metabolic or developmental factors. The authors hypothesise that insulin resistance may play a role in asthma and allergy.

A prospective study of asthma incidence and its predictors: the RHINE study

The objective of this longitudinal study was to estimate the incidence rate of asthma, and to compare the incidence between subjects with or without baseline reporting of certain respiratory symptoms. A follow-up of the random population samples in the European Respiratory Health Survey (ECRHS) in Sweden, Norway, Denmark, Iceland and Estonia was conducted in 1999-2001, in a population aged 30-54 yrs at follow-up (n=14,731). Asthma was defined as reporting either asthma or physician-diagnosed asthma, and a reported year when asthma symptoms were first noticed. Incidence rates, incidence rate ratios and hazard ratios were calculated with 95% confidence intervals. The incidence rate of asthma was 2.2 cases per 1,000 person-yrs. The incidence was higher among females (2.9 cases.1,000 person-yrs(-1)) than among males (1.5 cases.1,000 person-yrs(-1)). When subjects with baseline reporting of wheezing were excluded, the incidence rate decreased to 1.7 cases.1,000 person-yrs(-1), with a further decrease to 1.5 cases.1,000 person-yrs(-1) after exclusion of subjects with wheezing, nocturnal dyspnoea, chest tightness and cough. There was a strong association between onset of asthma and wheezing at baseline. In this prospective, population-based study, the incidence rate of asthma in the whole population sample ranged 1.5-2.2.1,000 person-yrs(-1), with a higher incidence range among females. The incidence was dependent on the extent to which subjects with respiratory symptoms were excluded from follow-up. Hence, for comparability between studies, the exclusion criteria in the follow-up population must be stated.

Insomnia is more common among subjects living in damp buildings

BACKGROUND

Insomnia is a condition with a high prevalence and a great impact on quality of life. Little is known about the relation between and sleep disturbances and the home environment.

AIM

To analyse the association between insomnia and building dampness.

METHODS

In a cross-sectional, multicentre, population study, 16 190 subjects (mean age 40 years, 53% women) were studied from Reykjavik in Iceland, Bergen in Norway, Umeå, Uppsala, and Göteborg in Sweden, Aarhus in Denmark, and Tartu in Estonia. Symptoms related to insomnia were assessed by questionnaire.

RESULTS

Subjects living in houses with reported signs of building dampness (n = 2873) had a higher prevalence of insomnia (29.4 v 23.6%; crude odds ratio 1.35, 95% CI 1.23 to 1.48). The association between insomnia and different indicators of building dampness was strongest for floor dampness: "bubbles or discoloration on plastic floor covering or discoloration of parquet floor" (crude odds ratio 1.96, 95% CI 1.66 to 2.32). The associations remained significant after adjusting for possible confounders such as sex, age, smoking history, housing, body mass index, and respiratory diseases. There was no significant difference between the centres in the association between insomnia and building dampness.

CONCLUSION

Insomnia is more common in subjects living in damp buildings. This indicates that avoiding dampness in building constructions and improving ventilation in homes may possibly have a positive effect on the quality of sleep.

Is birth weight related to lung function and asthma symptoms in Nordic-Baltic adults?

Studies of birth characteristics and respiratory outcomes show contradictory findings. We wanted to investigate the association of birth weight with adult lung function as well as asthma symptoms while addressing the influence of demographic and environmental factors. Data was collected from the birth records of 1683 men and women born in 1947-1973 who were included in 6 Nordic-Baltic population samples investigated within the European Community Respiratory Health Survey (ECRHS). In the adults, an increase in birth weight from below 2500 g to above 4000 g was associated with an increase from 96% to 104% predicted one-second forced expiratory volume (P<0.01) and from 1.00% to 107% predicted forced vital capacity (P<0.01). However, birth weight was not associated with symptoms of asthma. After adjustment for birth length, gender, age, study centre, adult BMI, allergic rhinitis, parental and adult tobacco smoke exposure in multivariate regression analyses, birth weight was not associated with adult lung function or asthma symptoms. Further sub-sample analyses revealed no influence of gestational age, gender, age or geographical area. In this historic prospective cohort study an association was neither found between birth weight and adult lung function nor between birth weight and asthma symptoms.

Increase in diagnosed asthma but not in symptoms in the European Community Respiratory Health Survey

BACKGROUND

Information on the epidemiology of asthma in relation to age is limited and hampered by reporting error. To determine the change in the prevalence of asthma with age in young adults we analysed longitudinal data from the European Community Respiratory Health Survey.

METHODS

A self-administered questionnaire was completed by 11 168 randomly selected subjects in 14 countries in 1991-3 when they were aged 20-44 years and 5-11 years later from 1998 to 2003. Generalised estimating equations were used to estimate net change in wheeze, nocturnal tightness in chest, shortness of breath, coughing, asthma attacks in the last 12 months, current medication, "diagnosed" asthma, and nasal allergies.

RESULTS

Expressed as change in status per 10 years of follow up, subjects reporting asthma attacks in the previous 12 months increased by 0.8% of the population (95% CI 0.2 to 1.4) and asthma medication by 2.1% (95% CI 1.6 to 2.6), while no statistically significant net change was found in reported symptoms. Reported nasal allergies increased, especially in the youngest age group.

CONCLUSIONS

As this cohort of young adults has aged, there has been an increase in the proportion treated for asthma but not in the proportion of those reporting symptoms suggestive of asthma. Either increased use of effective treatments has led to decreased morbidity among asthmatic subjects or those with mild disease have become more likely to label themselves as asthmatic.

Sensitization to house dust mites in Reykjavik, Iceland, in the absence of domestic exposure to mites

BACKGROUND

House dust mites are common sources of indoor allergens. In Reykjavik, Iceland, 9% of the young adult population had serum-specific IgE to Dermatophagoides pteronyssinus. Sensitization to mites is usually assumed to be due to exposure to house dust mites in the indoor environment. This investigation was carried out to measure the concentrations of house dust mite allergens and to investigate which species of mites were present in beds in Iceland.

METHODS

A total of 197 randomly selected adults were visited at home using the European Community Respiratory Health Survey (ECRHS) II Indoor protocol. Dust samples were collected from mattresses for measurement of house dust mite allergen concentrations and to estimate the number and type of house dust mites. Additional samples from mattresses and floors were collected from the homes of 10 patients with positive skin prick tests (SPT) to D. pteronyssinus. House dust mite allergen concentrations were measured using ELISA and examination of mite species was carried out using microscopy. Climatic parameters were assessed using psychrometer readings in the bedrooms and outdoors.

RESULTS

We found two single mite specimens, both D. pteronyssinus, in two dust samples. Mite allergen analyses indicated that two other dust samples had Der f 1 results close to the cut-off of 0.1 microg/g of dust. No samples were positive for Der p 1. In an additional collection of dust from the homes of 10 SPT-positive patients no Dermatophagoides spp. were found.

CONCLUSIONS

Reykjavik citizens are exposed to extremely low amounts of house dust mite allergens in their homes. Possible alternative sources for sensitization are discussed, such as bird nests, exposure from travelling abroad, or other mites or invertebrates that cross-react with house dust mite allergens. Our findings suggest that exposures other than to house dust mites indoors are possible sources of mite allergen exposure.

An international survey of chronic obstructive pulmonary disease in young adults according to GOLD stages

BACKGROUND

The recently published GOLD guidelines provide a new system for staging chronic obstructive pulmonary disease (COPD) from mild (stage I) to very severe (stage IV) and introduce a stage 0 (chronic cough and phlegm without airflow obstruction) that includes subjects "at risk" of developing the disease.

METHODS

In order to assess the prevalence of GOLD stages of COPD in high income countries and to evaluate their association with the known risk factors for airflow obstruction, data from the European Community Respiratory Health Survey on more than 18,000 young adults (20-44 years) were analysed.

RESULTS

The overall prevalence was 11.8% (95% CI 11.3 to 12.3) for stage 0, 2.5% (95% CI 2.2 to 2.7) for stage I, and 1.1% (95% CI 1.0 to 1.3) for stages II-III. Moderate to heavy smoking (> or =15 pack years) was significantly associated with both stage 0 (relative risk ratio (RRR)=4.15; 95% CI 3.55 to 4.84) and stages I+ (RRR=4.09; 95% CI 3.17 to 5.26), while subjects with stages I+ COPD had a higher likelihood of giving up smoking (RRR=1.39; 95% CI 1.04 to 1.86) than those with GOLD stage 0 (RRR=1.05; 95% CI 0.86 to 1.27). Environmental tobacco smoke had the same degree of positive association in both groups. Respiratory infections in childhood and low socioeconomic class were significantly and homogeneously associated with both groups, whereas occupational exposure was significantly associated only with stage 0. All the GOLD stages showed a significantly higher percentage of healthcare resource users than healthy subjects (p<0.001), with no difference between stage 0 and COPD.

CONCLUSIONS

A considerable percentage of young adults already suffered from COPD. GOLD stage 0 was characterised by the presence of the same risk factors as COPD and by the same high demand for medical assistance.

Allelic frequencies and patterns of single-nucleotide polymorphisms in candidate genes for asthma and atopy in Iceland

Numerous asthma and atopy loci have been reported in studies demonstrating associations of the asthma-related phenotypes atopy, elevated IgE levels, and bronchial hyperresponsiveness with alleles of microsatellite markers and single-nucleotide polymorphisms (SNPs) within specific cytokine/chemokine and IgE-regulating genes. Although the studies reporting these observations are compelling, most of them lack statistical power. We assessed the nature, pattern, and frequency of SNPs in 24 candidate genes in Iceland and looked for associations with asthma and atopy. We identified 42 SNPs with an average minor allele frequency of 20.3% (asthma) and 20.7% (control). Twenty SNPs (48%) were within coding sequences and 90% of those led to a predicted change in protein sequence. No differences were detected in the allelic frequencies of SNPs in any of these candidate genes between control subjects and the patients with atopic asthma. Moreover, linkage analysis that included 269 patients with atopic asthma uncovered no evidence of linkage to markers associated with these genes. We conclude that this study has failed to produce evidence in support of the notion that variations within these 24 candidate atopy and asthma genes significantly influence the expression of the atopic asthmatic phenotype or contribute to the susceptibility of atopic asthma.

Role of snoring and daytime sleepiness in occupational accidents

To establish whether snoring and excessive daytime sleepiness (EDS), the main symptoms of obstructive sleep apnea syndrome, influence the risk of occupational accidents a population-based, prospective study was performed. In 1984, 2,874 men aged 30-64 answered questions on snoring and EDS. Ten years later 2,009 (73.8% of the survivors) responded to a follow-up questionnaire including work-related questions and potential confounders. Information on occupational accidents during 1985-1994 was obtained from national register data. A total of 345 occupational accidents were reported by 247 of the men (12.3%). Multivariate analysis revealed that men who reported both snoring and EDS at baseline were at an increased risk of occupational accidents during the following 10 yr, with an adjusted odds ratio of 2.2 (95% CI 1.3-3.8) after adjusting for age, body mass index, smoking, alcohol dependence, years at work, blue-collar job, shift work, and exposure to noise, organic solvents, exhaust fumes, and whole-body vibrations. However, no significant increased risk was found for snorers without EDS or nonsnorers with EDS. We conclude that sleepy, male snorers have an increased risk of occupational accidents. The results indicate that early identification and treatment of sleep-disordered breathing may reduce the number of injuries at work.

Insomnia in men-a 10-year prospective population based study

STUDY OBJECTIVES

to prospectively analyze changes in the prevalence of insomnia and the relationship between insomnia, aging, lifestyle, and medical disorders

DESIGN

a longitudinal population survey.

PARTICIPANTS

a randomly selected population sample of 2,602 men (age 30-69 years) from Uppsala in Sweden.

INTERVENTION

all participants answered a questionnaire on sleep disturbances, lifestyle factors, and medical disorders in 1984 and again in 1994.

MEASUREMENTS AND RESULTS

The prevalence of INSOMNIA was 10.3% in 1984 and 12.8% in 1994. No significant correlation was found between age and insomnia in any of the two time periods. Insomnia in 1994 was independently related to having insomnia in 1984 (OR=6.45), being over-weight (BMI> 27 kg/m2) (OR=1.35), physical inactivity (OR=1.42), alcohol dependence (OR=1.75), psychiatric disorders (OR=8.27) and joint/low back disorders (OR=2.95). The number of subject with reported insomnia in 1984 but not 1994 was 149. Subjects that quit smoking during the time period had an increased likeliness of remission (OR=2.70) while men who were overweight were less likely to remit (OR=0.43).

CONCLUSIONS

We conclude that in men insomnia is related to lifestyle factors such as obesity, physical inactivity and alcohol dependency but not to aging. Medical disorders such as joint and low back disorders and psychiatric illnesses also increase the risk of reporting insomnia. This study demonstrates the close relationship between quality of sleep and overall health status.

Sleep-disordered breathing and glucose metabolism in hypertensive men: a population-based study

OBJECTIVES

Diabetes mellitus and obstructive sleep apnoea (OSA) are two prevalent medical problems. Both are strongly associated with obesity and hypertension. The aim of this study was to investigate whether the association between OSA and diabetes is entirely dependent on obesity in hypertensive men.

DESIGN

A population-based study.

SETTING

The municipality of Uppsala, Sweden. Subjects and methods. In 1994, 2668 men aged 40-79 years answered a questionnaire regarding snoring, sleep disturbances and somatic diseases. An age-stratified sample of 116 hypertensive men was selected for a whole-night sleep study. Twenty-five of them had diabetes, defined as reporting regular medical controls for diabetes or having a fasting blood glucose > or =6.1 mmol L(-1).

RESULTS

The prevalence of severe OSA, defined as apnoea-hypopnoea index (AHI) > or =20 h(-1) was significantly higher in diabetic patients than in normoglycaemic subjects (36 vs. 14.5%, P < 0.05). The sample was divided into four groups based on the presence or absence of severe OSA and the presence or absence of central obesity, defined as waist-to-hip ratio (WHR) > or =1.0. In a logistic regression model with the non-OSA, WHR <1.0 as the reference group, the adjusted odds ratio (95% confidence interval) for diabetes was 11.8 (2.0-69.8) in the OSA, WHR > or =1.0 group, whilst it was 3.6 (0.9-14.8) in the non-OSA, WHR > or =1.0 group and 5.7 (0.3-112) in the OSA, WHR <1.0 group. In a linear regression model, after adjustment for WHR, there was a significant relationship between variables of sleep-disordered breathing and fasting insulin, glucose and haemoglobin A1c.

CONCLUSIONS

We conclude that, in hypertensive men, although obesity is the main risk factor for diabetes, coexistent severe OSA may add to this risk. Sleep breathing disorders, independent of central obesity, may influence plasma insulin and glycaemia.

CLINICAL REVIEW ARTICLE: Epidemiology of sleep-related obstructive breathing

The diagnosis of obstructive sleep apnoea syndrome (OSAS) and upper airway resistance syndrome (UARS) is based both on a combination of laboratory findings from whole-night sleep recordings and daytime symptoms. Due to the recent interest in breathing disturbances during sleep many prevalence studies have been performed within this field. There are, however, methodological difficulties in characterizing these syndromes in large populations; many of the studies have therefore been unable to present an overview of the complete syndromes but rather have focused on specific characteristics. In epidemiological research snoring and/or daytime sleepiness have often been used as markers of OSAS, while other studies have looked only on the respiratory disturbances or oxygen desaturation. Studies on the prevalence of OSAS based on polysomnography are reviewed here, as well as investigations where associated factors such as cardiovascular diseases and mortality were analysed. The interrelationships between snoring, daytime symptoms and laboratory findings are discussed. Gender, age, obesity, smoking, alcohol and ethnicity are all factors that influence the prevalence of OSAS. The data on associations between OSAS and cardiovascular disease or mortality are sometimes unrelated. Much of the discrepancy between different studies can be explained by the methodological difficulties connected with the definition of OSAS and also by the fact that the association between sleep-disordered breathing and cardiovascular outcome seems to be age-dependent.