Effects of oral roflumilast therapy on body weight and cardiometabolic parameters in patients with psoriasis - results from a randomized controlled trial (PSORRO).

BACKGROUND: Weight loss is reported with oral roflumilast, which is approved for chronic obstructive pulmonary disease (COPD). Recently, the drug has shown efficacy in psoriasis, a disease strongly linked to overweight/obesity. OBJECTIVE: To describe the effects of oral roflumilast on body weight and cardio-metabolic parameters in patients with psoriasis. METHODS: Posthoc analyses from the PSORRO study, where patients with moderate-to-severe plaque psoriasis were randomized 1:1 to oral roflumilast 500 µg once-daily or placebo for 12 weeks, followed by active, open-label treatment through week 24 in both groups. Changes in body weight, blood pressure, gastrointestinal symptoms, and laboratory tests were registered. No lifestyle or dietary interventions were applied. RESULTS: Forty-six patients were randomized. Baseline characteristics across groups were comparable; mean weight was 103.6 kg. In patients receiving roflumilast, median weight change was -2.6% and -4% at week 12 and 24, respectively. Corresponding numbers were 0.0% and 1.3% in patients initially allocated to placebo. Reduced appetite was more frequent with active therapy. No changes in blood pressure or laboratory tests were observed. LIMITATIONS: Posthoc analyses and low numbers. CONCLUSION: Oral roflumilast induced weight loss and reduced appetite, which support the growing evidence of roflumilast as an attractive treatment alternative for patients with psoriasis.

Artificial intelligence and allergic rhinitis: does ChatGPT increase or impair the knowledge?

BACKGROUND: Optimal management of allergic rhinitis requires patient education with easy access to accurate information. However, previous online platforms have provided misleading information. The demand for online medical information continues to grow, especially with the introduction of advanced chatbots like ChatGPT. METHODS: This study aimed to evaluate the quality of information provided by ChatGPT regarding allergic rhinitis. A Likert scale was used to assess the accuracy of responses, ranging from 1 to 5. Four authors independently rated the responses from a healthcare professional's perspective. RESULTS: A total of 20 questions covering various aspects of allergic rhinitis were asked. Among the answers, eight received a score of 5 (no inaccuracies), five received a score of 4 (minor non-harmful inaccuracies), six received a score of 3 (potentially misinterpretable inaccuracies) and one answer had a score of 2 (minor potentially harmful inaccuracies). CONCLUSIONS: The variability in accuracy scores highlights the need for caution when relying solely on chatbots like ChatGPT for medical advice. Patients should consult qualified healthcare professionals and use online sources as a supplement. While ChatGPT has advantages in medical information delivery, its use should be approached with caution. ChatGPT can be useful for patient education but cannot replace healthcare professionals.

The usefulness of YouTube videos as a source of information in asthma.

BACKGROUND: Patient education is a key element in the management of asthma. AIMS: This study aimed to evaluate the popularity and usefulness of YouTube videos on asthma. METHODS: Two authors screened and evaluated the 200 most popular videos. Data on likes, dislikes, views, comment, source of uploader, days since upload, and usefulness were recorded and included for analyses. The usefulness of the videos was categorized as follows: useful, misleading, or neutral. Misleading videos provided at least one scientifically incorrect detail, whereas useful videos contained scientifically correct information. RESULTS: A total of 130 videos were included, and the total number of views was 100,290,242 with a total duration of 29 h and 8 min. While 26.6% of videos were uploaded by TV shows and YouTube channels, only 7.7% were uploaded by lung specialists. 65.4% of the videos contained scientifically correct information, whereas 18.5% contained misleading information. Although videos from medical professionals had a higher quality than videos from YouTube channels and TV shows, the latter were more popular. Misleading videos had numerically, but not statistically significant higher views compared with useful videos. CONCLUSIONS: YouTube videos on asthma are popular in terms of viewer interaction, and the popularity is not restricted to videos uploaded by professional sources. Although more than half of the videos were found to be useful, a non-negligible proportion of videos were assessed as misleading. The usefulness of YouTube videos on asthma is variable and initiatives should be taken to increase the potential of YouTube as an useful source in patient education.

The usefulness of YouTube videos on lung cancer.

BACKGROUND: The use of social media as a source of health information is increasing, and the usefulness of the content may vary depending on the specific disease. Thus, this study was designed to assess the content, viewer engagement and usefulness of the most viewed YouTube videos on lung cancer. METHODS: 167 videos were reviewed, and 143 met the eligibility criteria. Two authors evaluated the videos separately, and data on views, likes, dislikes and comments were extracted, and data on the source of uploader, duration and content quality were recorded. RESULTS: 89 videos (62%) were classified as useful, 8 (6%) as misleading and 46 (32%) as neither. The misleading videos were significantly more popular in terms of views and likes compared with the useful videos: 845 643 versus 81 700, P = 0.003 and 12 170 versus 415, P < 0.001, respectively. CONCLUSIONS: This study shows that YouTube videos on lung cancer are popular and that around two-thirds of the videos are useful in terms of patient education. However, the misleading videos are currently attracting higher viewer interaction and might compose a future challenge in terms of the spread of misinformation as the algorithms will prioritize popular videos rather than videos with evidence-based information.

Use of inhaled corticosteroids and risk of acquiring Pseudomonas aeruginosa in patients with chronic obstructive pulmonary disease.

BACKGROUND: Inhaled corticosteroids (ICS) are commonly used to treat COPD and are associated with increased risk of pneumonia. The aim of this study was to assess if accumulated use of ICS is associated with a dose-dependent risk of a positive airway culture with Pseudomonas aeruginosa in patients with COPD. METHODS: We conducted a multiregional epidemiological cohort study including Danish COPD patients followed in outpatient clinics during 2010-2017. ICS use was categorised based on accumulated prescriptions redeemed 365 days prior to cohort entry. Cox proportional hazard regression model was used to estimate the risk of acquiring P. aeruginosa. Propensity score matched models were used as sensitivity analyses. RESULTS: A total of 21 408 patients were included in the study, of which 763 (3.6%) acquired P. aeruginosa during follow-up. ICS use was associated with a dose-dependent risk of P. aeruginosa (low ICS dose: HR 1.38, 95% CI 1.03 to 1.84, p=0.03; moderate ICS dose: HR 2.16, 95% CI 1.63 to 2.85, p<0.0001; high ICS dose: HR 3.58, 95% CI 2.75 to 4.65, p<0.0001; reference: no ICS use). A propensity matched model confirmed the results (high ICS dose compared with no/low/moderate ICS dose: HR 2.05, 95% CI 1.76 to 2.39, p p<0.0001). CONCLUSION: Use of ICS in patients with COPD followed in Danish outpatient clinics was associated with a substantially increased and dose-dependent risk of acquiring P. aeruginosa. Caution should be taken when administering high doses of ICS in severely ill patients with COPD. These results should be confirmed in comparable cohorts and other settings.

Azithromycin and hydroxychloroquine in hospitalised patients with confirmed COVID-19: a randomised double-blinded placebo-controlled trial.

BACKGROUND: Combining the antibiotic azithromycin and hydroxychloroquine induces airway immunomodulatory effects, with the latter also having in vitro antiviral properties. This may improve outcomes in patients hospitalised for coronavirus disease 2019 (COVID-19). METHODS: Placebo-controlled double-blind randomised multicentre trial. Patients aged ≥18 years, admitted to hospital for ≤48 h (not intensive care) with a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse transcription PCR test were recruited. The intervention was 500 mg daily azithromycin for 3 days followed by 250 mg daily azithromycin for 12 days combined with 200 mg twice-daily hydroxychloroquine for all 15 days. The control group received placebo/placebo. The primary outcome was days alive and discharged from hospital within 14 days (DAOH14). RESULTS: After randomisation of 117 patients, at the first planned interim analysis, the data and safety monitoring board recommended stopping enrolment due to futility, based on pre-specified criteria. Consequently, the trial was terminated on 1 February 2021. 61 patients received the combined intervention and 56 patients received placebo. In the intervention group, patients had a median (interquartile range) 9.0 (3-11) DAOH14 versus 9.0 (7-10) DAOH14 in the placebo group (p=0.90). The primary safety outcome, death from all causes on day 30, occurred for one patient in the intervention group versus two patients receiving placebo (p=0.52), and readmittance or death within 30 days occurred for nine patients in the intervention group versus six patients receiving placebo (p=0.57). CONCLUSIONS: The combination of azithromycin and hydroxychloroquine did not improve survival or length of hospitalisation in patients with COVID-19.

YouTube as a source of (mis)information on allergic rhinitis.

BACKGROUND: Allergic rhinitis is a very common chronic condition that affects nearly one-quarter of the adult population worldwide. The optimal management of allergic rhinitis includes useful information on several aspects of the condition. Social media and online platforms are increasingly being used to obtain health-related information. OBJECTIVE: The study aimed to evaluate and evaluate the popularity and usefulness of YouTube videos on allergic rhinitis. METHODS: Out of 225 screened videos, 86 met the inclusion criteria. A scoring scheme was designed to evaluate and rate the content of the extracted data. Data on views, likes, dislikes, and comments were extracted, and data on the source of uploader, duration, and content quality were recorded. RESULTS: A total of 43% of the videos were classified as useful, 36% as misleading, and 21% as neither useful nor misleading. Although professional health care providers uploaded two-thirds of the videos, they accounted for only 24.4% of the total videos. Videos uploaded by television shows and YouTube channels had by far the most user interaction, accounting for 66.9% of the total likes, 66.8% of the total dislikes, and 54.0% of the total comments. This source alone accounted for 23.4% of the total views, but for 48% of the total misleading videos. CONCLUSION: The usefulness of YouTube videos on allergic rhinitis is varying and less than half of the videos provided useful information. If the proper conditions are met, selected YouTube videos on allergic rhinitis can be used as a source of information for patient education.

Use of inhaled corticosteroids and the risk of developing type 2 diabetes in patients with chronic obstructive pulmonary disease.

AIM: To determine the risk of type 2 diabetes onset associated with accumulated inhaled corticosteroids (ICS) dose during the previous year in patients with chronic obstructive pulmonary disease (COPD). MATERIALS AND METHODS: We conducted a nationwide observational cohort study based on data from patients with COPD between 1 January 2010 and 31 December 2017 extracted from Danish health databases. Patients were followed for 7 years, until death or a type 2 diabetes event. A propensity-matched Cox model and an adjusted Cox proportional hazards model (stratified on body mass index [BMI]) were used to estimate the hazard ratio (HR) for new-onset type 2 diabetes. RESULTS: A total of 50 148 patients with COPD were included, 3566 (7.1%) of whom had a type 2 diabetes event. During the previous year before study entry, 35 368 patients (70.5%) used ICS. The propensity-matched Cox model (N = 33 466) showed an increased risk of type 2 diabetes, which progressed with increasing accumulated ICS dose (low-ICS: HR 1.076, confidence interval [CI] 1.075-1.077, P < .0001; medium-ICS: HR 1.106, CI 1.105-1.108, P < .0001; high-ICS: HR 1.150, CI 1.148-1.151, P < .0001), compared with no ICS use. Results were confirmed in the adjusted Cox analysis on the entire study population, but only for patients with BMI <30 kg/m2 . CONCLUSIONS: In patients with COPD, ICS use was associated with a moderate dose-dependent increase in the occurrence of type 2 diabetes.

Association Between Chronic Obstructive Pulmonary Disease and Type 2 Diabetes: A Systematic Review and Meta-Analysis.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) has been associated with an increased risk of type 2 diabetes (T2D). However, the mechanisms linking COPD and T2D is not fully understood and contradicting results are reported in the literature. AIM: The aim of this study is to investigate whether COPD is associated with an increased risk of T2D. METHODS: A systematic review and meta-analysis of cohort and case-control studies were performed. Search for studies and data extraction was carried out by two authors independently. Study quality was assessed by NOS. Adjusted data were pooled using the random effects model to calculate summary odds ratios (ORs) with corresponding 95% confidence intervals (CIs). RESULTS: We identified four cohort studies and three case-control studies with a total of 1,369,560 participants of whom 42,716 were COPD patients. The quality of the studies was acceptable, with an average on 7.7 indicating overall good study quality. The meta-analysis on adjusted data from all seven studies showed that the COPD group had a higher risk of T2D compared with the non-COPD group: random effect OR = 1.17 (1.01-1.35), p = 0.03. No heterogeneity was found I2 = 0%. When including only studies diagnosing both COPD and T2D according to recommended guidelines the association did not remain statistically significant, OR =1.17 (0.96-1.42), p = 0.12. CONCLUSION: This systemic review and meta-analyses showed that the association between COPD and T2D might be influenced by the diagnostic method and should be further investigated in studies using diagnostic definition according to guidelines. Nevertheless, physicians should be aware of comorbidities in COPD patients.

Natural history of skin prick test reactivity: A 20-year prospective study of a random population sample of children and adolescents.

BACKGROUND: Allergic reactions to airborne allergens may have important consequences for affected individuals and are believed to be unstable through life, although evidence from longitudinal studies is limited. OBJECTIVE: To assess changes in skin prick reactivity during 20 years in a random population sample of children and adolescents in relation to symptoms of rhinitis. METHODS: A total of 983 individuals, aged 7 to 17 years, were randomly selected in 1986 and invited to 4 examinations during a 20-year period. During each examination, a skin prick test was performed using common local aeroallergens (ie, birch, grass, mugwort, horse, dog, cat, house dust mite [Dermatophagoides pteronyssinus and Dermatophagoides farinae] and 2 molds [Alternaria iridis and Cladosporium herbarum]). RESULTS: The prevalence of allergy to any tested allergen peaked at the ages of 13 to 23 years. Rates of sensitization were variable. In the group of individuals tested more than once (n = 592), 16% developed sensitization during the study period and 9% became desensitized. In the group of individuals tested at all 4 examinations (n = 148), 34% developed sensitization and 22% became desensitized. In the group who developed sensitization, 55% had rhinitis, 17% had asthma, and 70% had eczema. In the group who became desensitized, 30% had rhinitis, 10% had asthma, and 50% had eczema. CONCLUSION: This 20-year prospective study found that sensitization is common, but its prevalence in individuals is also variable over time. Furthermore, through puberty and early adulthood a large number of individuals develop sensitization and a smaller number become desensitized. In addition, we found that symptoms of rhinitis rarely preceded sensitization.

Novel monoclonal treatments in severe asthma.

AIM: To provide a general overview of the current biological treatments and discuss their potential anti-asthmatic effects. DATA SOURCES: We reviewed articles in PubMed found using the search words "Asthma/therapy AND antibodies, monoclonal/therapeutic use AND cytokines." STUDY SELECTIONS: Only articles published in English since 2000 were considered. The search identified 29 studies; 8 additional studies were found by hand search, generating 37 studies. RESULTS: Of the 37 studies investigating biological treatments of asthma, 5 were on the effects of anti-IgE (omalizumab); 12 on anti-IL-5; 8 on anti-IL-13; 5 on anti-IL-4R-α; 3 on anti-IL-9; one on TNF-α; one on anti-IL-2R-α; one on TSLP (Thymic Stromal Lymphopoietin); and one on OX40L. Sample sizes ranged from 3 to 943 participants. Studies of therapies targeting IgE, IL-2, IL4R-α, IL-5, and IL-13 showed some efficacy, whereas those targeting TSLP, IL-9, and TNF-α lacked convincing effectiveness. CONCLUSION: Research on the biological treatment of asthma shows promising results. While anti-IgE (omalizumab) has been used in the treatment of asthma for some years, anti-IL-5 has recently been approved for use. The efficacy of results of other large studies with a longer duration is needed to draw a firm conclusion. Such studies should not only focus on clinical outcomes, but also consider asthma-related quality of life. Knowledge on the asthma phenotypes and identification of biomarkers associated with these will be useful for physicians considering the right treatment for the asthma patient.

Evaluating the scientific reliability of ChatGPT as a source of information on asthma.

Background: This study assessed the reliability of ChatGPT as a source of information on asthma, given the increasing use of artificial intelligence-driven models for medical information. Prior concerns about misinformation on atopic diseases in various digital platforms underline the importance of this evaluation. Objective: We aimed to evaluate the scientific reliability of ChatGPT as a source of information on asthma. Methods: The study involved analyzing ChatGPT's responses to 26 asthma-related questions, each followed by a follow-up question. These encompassed definition/risk factors, diagnosis, treatment, lifestyle factors, and specific clinical inquiries. Medical professionals specialized in allergic and respiratory diseases independently assessed the responses using a 1-to-5 accuracy scale. Results: Approximately 81% of the responses scored 4 or higher, suggesting a generally high accuracy level. However, 5 responses scored >3, indicating minor potentially harmful inaccuracies. The overall median score was 4. Fleiss multirater kappa value showed moderate agreement among raters. Conclusion: ChatGPT generally provides reliable asthma-related information, but its limitations, such as lack of depth in certain responses and inability to cite sources or update in real time, were noted. It shows promise as an educational tool, but it should not be a substitute for professional medical advice. Future studies should explore its applicability for different user demographics and compare it with newer artificial intelligence models.

ERS International Congress 2023: highlights from the Epidemiology and Environment Assembly.

In this article, early career members of the Epidemiology and Environment Assembly of the European Respiratory Society (ERS) summarise a selection of four poster and oral sessions from the ERS 2023 Congress. The topics covered the following areas: micro- and macro-environments and respiratory health, occupational upper and lower airway diseases, selected tobacco and nicotine research, and multimorbidity in people with lung diseases. The topics and studies covered in this review illustrate the broad range of the multifaceted research taking place within Assembly 6, from the identification of indoor and outdoor environmental risk factors for the development and worsening of respiratory diseases to the concerningly increasing use of nicotine products and their health consequences beyond respiratory health and comorbidity in respiratory diseases.

Psychiatric Adverse Effects of Montelukast-A Nationwide Cohort Study.

BACKGROUND: Recent observational studies suggest that the leukotriene receptor antagonist montelukast may have neuropsychiatric adverse effects; however, results are conflicting. OBJECTIVE: To assess whether montelukast exposure in adults with asthma is associated with onset of neuropsychiatric adverse events using data from the Danish nationwide health registers. METHODS: Individuals 18 years old or older with either 1 or more prescription redemption of inhaled corticosteroids or with at least 1 hospital contact with asthma as the main diagnosis between January 1, 2011, and December 31, 2018, were included. Montelukast exposure was assessed as a time-dependent variable. The 2 outcomes of interest were use of neuropsychiatric medicine including antidepressants, antipsychotics, anxiolytics, lithium, and medication used for attention-deficit/hyperactivity disorder (outcome 1), and hospital contacts with a neuropsychiatric diagnosis (outcome 2), within 90 days of exposure to montelukast. RESULTS: Initiation of montelukast was significantly associated with outcome 1: use of neuropsychiatric medicine (hazard ratio [95% confidence interval]) 1.14 [1.08-1.20]; P < .0001). In the assessment of outcome 2: hospital contacts with a neuropsychiatric diagnosis, a significant risk associated with montelukast initiation was found only in the youngest age groups (hazard ratio [95% confidence interval] 1.28 [1.12-1.47], P < .001 and 1.16 [1.02-1.31]; P < .05, for age group 18-29 y and 30-44 y, respectively). Age-stratified analyses showed that the risk of both outcomes increased with decreasing age, with the highest risk seen in patients aged 18 to 29 years. CONCLUSIONS: Among younger individuals, montelukast use was significantly associated with an increased risk of neuropsychiatric events such as use of neuropsychiatric medicine and hospital treatment. Clinicians should increase awareness of such adverse effects when prescribing montelukast.

Efficacy and safety of oral roflumilast for moderate-to-severe psoriasis-a randomized controlled trial (PSORRO).

Background: Roflumilast is a targeted inhibitor of phosphodiesterase (PDE)-4 and has been approved for treatment of severe chronic obstructive pulmonary disease for more than a decade. Generic versions are available in the United States. PDE-4 is involved in the psoriasis pathogenesis, but the efficacy and safety of oral roflumilast in patients with psoriasis have not previously been studied. Methods: A company-independent, multicenter, randomized, double-blind, placebo-controlled trial (ClinicalTrials.govNCT04549870). Patients were randomized 1:1 to receive monotherapy with oral roflumilast 500 µg once daily or placebo. At week 12, placebo patients were switched to open-label roflumilast through week 24. The primary endpoint was a 75% or greater reduction from baseline in the psoriasis area and severity index (PASI75) at week 12. Findings: In all, 46 patients were randomized (roflumilast, n = 23; placebo, n = 23). At week 12, significantly more patients in the active arm achieved PASI75 (8 of 23 patients [35%]) vs. placebo (0 of 23 patients [0%], with a difference vs. placebo of 8 [35%] patients, 95% CI: 3 [13%]-13 [57%] patients) (p = 0.014). At week 24, 15 (65%), 10 (44%), 5 (22%), and 2 (9%) of patients treated with roflumilast from week 0 had PASI50, PASI75, PASI90, and PASI100 responses (key secondary endpoints), respectively. The most prevalent, drug-related adverse events in both treatment groups were transient gastrointestinal symptoms, weight-loss, headache, and insomnia. A total of three patients (roflumilast n = 2; placebo, n = 1) discontinued therapy due to adverse events. Interpretation: Oral roflumilast was efficacious and safe in treating moderate-to-severe plaque psoriasis over 24 weeks. With generic versions available, this drug may represent an inexpensive and convenient alternative to established systemic psoriasis treatments. Funding: Financial support was received from Herlev and Gentofte Hospital, University of Copenhagen, and independent grants from private foundations in Denmark. No pharmaceutical company, including the market authorization holder of roflumilast, was involved in the study at any point.

Phenotyping asthma with airflow obstruction in middle-aged and older adults: a CADSET clinical research collaboration.

BACKGROUND: The prevalence and clinical profile of asthma with airflow obstruction (AO) remain uncertain. We aimed to phenotype AO in population- and clinic-based cohorts. METHODS: This cross-sectional multicohort study included adults ≥50 years from nine CADSET cohorts with spirometry data (N=69 789). AO was defined as ever diagnosed asthma with pre-BD or post-BD FEV1/FVC <0.7 in population-based and clinic-based cohorts, respectively. Clinical characteristics and comorbidities of AO were compared with asthma without airflow obstruction (asthma-only) and chronic obstructive pulmonary disease (COPD) without asthma history (COPD-only). ORs for comorbidities adjusted for age, sex, smoking status and body mass index (BMI) were meta-analysed using a random effects model. RESULTS: The prevalence of AO was 2.1% (95% CI 2.0% to 2.2%) in population-based, 21.1% (95% CI 18.6% to 23.8%) in asthma-based and 16.9% (95% CI 15.8% to 17.9%) in COPD-based cohorts. AO patients had more often clinically relevant dyspnoea (modified Medical Research Council score ≥2) than asthma-only (+14.4 and +14.7 percentage points) and COPD-only (+24.0 and +5.0 percentage points) in population-based and clinic-based cohorts, respectively. AO patients had more often elevated blood eosinophil counts (>300 cells/µL), although only significant in population-based cohorts. Compared with asthma-only, AO patients were more often men, current smokers, with a lower BMI, had less often obesity and had more often chronic bronchitis. Compared with COPD-only, AO patients were younger, less often current smokers and had less pack-years. In the general population, AO patients had a higher risk of coronary artery disease than asthma-only and COPD-only (OR=2.09 (95% CI 1.26 to 3.47) and OR=1.89 (95% CI 1.10 to 3.24), respectively) and of depression (OR=1.41 (95% CI 1.19 to 1.67)), osteoporosis (OR=2.30 (95% CI 1.43 to 3.72)) and gastro-oesophageal reflux disease (OR=1.68 (95% CI 1.06 to 2.68)) than COPD-only, independent of age, sex, smoking status and BMI. CONCLUSIONS: AO is a relatively prevalent respiratory phenotype associated with more dyspnoea and a higher risk of coronary artery disease and elevated blood eosinophil counts in the general population compared with both asthma-only and COPD-only.

Risk of chronic bronchitis in twin pairs discordant for smoking.

BACKGROUND: It is well known that smoking is a major risk factor for lung disease and respiratory symptoms. We examined the association between smoking and the risk of chronic bronchitis in a large twin sample. METHODS: In a population-based questionnaire study of 13,649 twins, aged 50-71 years, from the Danish Twin Registry, we identified 1,146 twin pairs, discordant for a lifetime history smoking. We performed co-twin control analysis to examine the impact of smoking on the risk of chronic bronchitis. RESULTS: The prevalence of chronic bronchitis was 9.7 %. In the total sample, high age, living without a spouse, and smoking remained statistically significant predictors with an up to tenfold increased risk of chronic bronchitis in the heaviest smokers compared with never-smokers, after multivariate adjustment. Among twin pairs discordant for smoking, chronic bronchitis was significantly more common in the smoking twin compared with the nonsmoking co-twin. There was no differential effect of smoking on the risk of chronic bronchitis in monozygotic and dizygotic twins. CONCLUSIONS: The risk of chronic bronchitis increases with age and increasing tobacco consumption. The results indicate a direct relationship between smoking and development of chronic bronchitis, but other environmental factors, such as exposure to household smoking in childhood and living without a spouse, also play a role.