Factors Associated with Attrition in a Longitudinal Cohort of Older Adults in the Community.

Introduction: Retaining participants in longitudinal studies increases their power. We undertook this study in a population-based longitudinal cohort of adults with COPD to determine the factors associated with increased cohort attrition. Methods: In the longitudinal population-based Canadian Cohort of Obstructive Lung Disease (CanCOLD) study, 1561 adults > 40 years old were randomly recruited from 9 urban sites. Participants completed in-person visits at 18-month intervals and also were followed up every 3 months over the phone or by email. The cohort retention for the study and the reasons for attrition were analyzed. Hazard ratios and robust standard errors were calculated using Cox regression methods to explore the associations between participants who remained in the study and those who did not. Results: The median follow-up (years) of the study is 9.0 years. The overall mean retention was 77%. Reasons for attrition (23%) were: dropout by participant (39%), loss of contact (27%), investigator-initiated withdrawal (15%), deaths (9%), serious disease (9%), and relocation (2%). Factors independently associated with attrition were lower educational attainment, higher pack-year tobacco consumption, diagnosed cardiovascular disease, and a higher Hospital Anxiety and Depression Scale score: adjusted hazard ratios (95% confidence interval) were 1.43(1.11, 1.85); 1.01(1.00, 1.01); 1.44(1.13, 1.83); 1.06(1.02, 1.10) respectively. Conclusions: Identification and awareness of risk factors for attrition could direct targeted retention strategies in longitudinal studies. Moreover, the identification of patient characteristics associated with study dropout could address any potential bias introduced by differential dropouts.

Aryl hydrocarbon receptor deficiency causes the development of chronic obstructive pulmonary disease through the integration of multiple pathogenic mechanisms.

Emphysema, a component of chronic obstructive pulmonary disease (COPD), is characterized by irreversible alveolar destruction that results in a progressive decline in lung function. This alveolar destruction is caused by cigarette smoke, the most important risk factor for COPD. Only 15%-20% of smokers develop COPD, suggesting that unknown factors contribute to disease pathogenesis. We postulate that the aryl hydrocarbon receptor (AHR), a receptor/transcription factor highly expressed in the lungs, may be a new susceptibility factor whose expression protects against COPD. Here, we report that Ahr-deficient mice chronically exposed to cigarette smoke develop airspace enlargement concomitant with a decline in lung function. Chronic cigarette smoke exposure also increased cleaved caspase-3, lowered SOD2 expression, and altered MMP9 and TIMP-1 levels in Ahr-deficient mice. We also show that people with COPD have reduced expression of pulmonary and systemic AHR, with systemic AHR mRNA levels positively correlating with lung function. Systemic AHR was also lower in never-smokers with COPD. Thus, AHR expression protects against the development of COPD by controlling interrelated mechanisms involved in the pathogenesis of this disease. This study identifies the AHR as a new, central player in the homeostatic maintenance of lung health, providing a foundation for the AHR as a novel therapeutic target and/or predictive biomarker in chronic lung disease.

Findings on Thoracic Computed Tomography Scans and Respiratory Outcomes in Persons with and without Chronic Obstructive Pulmonary Disease: A Population-Based Cohort Study.

BACKGROUND: Thoracic computed tomography (CT) scans are widely performed in clinical practice, often leading to detection of airway or parenchymal abnormalities in asymptomatic or minimally symptomatic individuals. However, clinical relevance of CT abnormalities is uncertain in the general population. METHODS: We evaluated data from 1361 participants aged ≥40 years from a Canadian prospective cohort comprising 408 healthy never-smokers, 502 healthy ever-smokers, and 451 individuals with spirometric evidence of chronic obstructive pulmonary disease (COPD) who had thoracic CT scans. CT images of subjects were visually scored for respiratory bronchiolitis(RB), emphysema(E), bronchial-wall thickening(BWT), expiratory air-trapping(AT), and bronchiectasis(B). Multivariable logistic regression models were used to assess associations of CT features with respiratory symptoms, dyspnea, health status as determined by COPD assessment test, and risk of clinically significant exacerbations during 12 months follow-up. RESULTS: About 11% of life-time never-smokers demonstrated emphysema on CT scans. Prevalence increased to 30% among smokers with normal lung function and 36%, 50%, and 57% among individuals with mild, moderate or severe/very severe COPD, respectively. Presence of emphysema on CT was associated with chronic cough (OR,2.11; 95%CI,1.4-3.18); chronic phlegm production (OR,1.87; 95% CI,1.27-2.76); wheeze (OR,1.61; 95% CI,1.05-2.48); dyspnoea (OR,2.90; 95% CI,1.41-5.98); CAT score≥10(OR,2.17; 95%CI,1.42-3.30) and risk of ≥2 exacerbations over 12 months (OR,2.17; 95% CI, 1.42-3.0). CONCLUSIONS: Burden of thoracic CT abnormalities is high among Canadians ≥40 years of age, including never-smokers and smokers with normal lung function. Detection of emphysema on CT scans is associated with pulmonary symptoms and increased risk of exacerbations, independent of smoking or lung function.

Lung Function and Bronchial Hyperresponsiveness in Adults Born Prematurely. A Cohort Study.

RATIONALE: Bronchopulmonary dysplasia and the long-term consequences of prematurity are underrecognized entities, unfamiliar to adult clinicians. Well described by the pediatric community, these young adults are joining the ranks of a growing population of adults with chronic lung disease. OBJECTIVES: To describe the quality of life, pulmonary lung function, bronchial hyperresponsiveness, body composition, and trends in physical activity of adults born prematurely, with or without respiratory complications. METHODS: Four groups of young adults born in Canada between 1987 and 1993 were enrolled in a cohort study: (1) preterm subjects with no neonatal respiratory complications, (2) preterm subjects with neonatal respiratory distress syndrome, (3) preterm subjects with bronchopulmonary dysplasia, and (4) subjects born at term. The following measurements were compared across the four groups: health-related quality of life, respiratory health, pulmonary function, methacholine challenge test results, and sedentary behavior and physical activity level. MEASUREMENTS AND MAIN RESULTS: Adult subjects who had bronchopulmonary dysplasia in infancy had mild airflow obstruction (FEV1, 80% predicted; FEV1/FCV ratio, 70) and gas trapping compared with others. They also had less total active energy expenditure and more time spent in sedentary behavior compared with subjects born at term. All preterm groups had a high prevalence of bronchial hyperresponsiveness compared with term subjects. CONCLUSIONS: In a population-derived, cross-sectional study, we confirmed previous reports that adults 21 or 22 years of age who were born prematurely with neonatal bronchopulmonary dysplasia are more likely to have airflow obstruction, bronchial hyperresponsiveness, and pulmonary gas trapping than subjects born prematurely without bronchopulmonary dysplasia or at term. Clinicians who care for adults need to be better informed of the long-term respiratory consequences of premature birth to assist young patients in maintaining lung function and health.

Decreased expression of the NF-κB family member RelB in lung fibroblasts from Smokers with and without COPD potentiates cigarette smoke-induced COX-2 expression.

BACKGROUND: Heightened inflammation, including expression of COX-2, is associated with COPD pathogenesis. RelB is an NF-κB family member that attenuates COX-2 in response to cigarette smoke by a mechanism that may involve the miRNA miR-146a. There is no information on the expression of RelB in COPD or if RelB prevents COX-2 expression through miR-146a. METHODS: RelB, Cox-2 and miR-146a levels were evaluated in lung fibroblasts and blood samples derived from non-smokers (Normal) and smokers (At Risk) with and without COPD by qRT-PCR. RelB and COX-2 protein levels were evaluated by western blot. Human lung fibroblasts from Normal subjects and smokers with and without COPD, along with RelB knock-down (siRNA) in Normal cells, were exposed to cigarette smoke extract (CSE) in vitro and COX-2 mRNA/protein and miR-146a levels assessed. RESULTS: Basal expression of RelB mRNA and protein were significantly lower in lung cells derived from smokers with and without COPD, the latter of which expressed more Cox-2 mRNA and protein in response to CSE. Knock-down of RelB in Normal fibroblasts increased Cox-2 mRNA and protein induction by CSE. Basal miR-146a levels were not different between the three groups, and only Normal fibroblasts increased miR-146a expression in response to smoke. There was a positive correlation between systemic RelB and Cox-2 mRNA levels and circulating miR-146a levels were higher only in GOLD stage I subjects. CONCLUSIONS: Our data indicate that RelB attenuates COX-2 expression in lung structural cells, such that loss of pulmonary RelB may be an important determinant in the aberrant, heightened inflammation associated with COPD pathogenesis.

Derivation of normative data for the COPD assessment test (CAT).

BACKGROUND: The tradition classification of the severity of COPD, based on spirometry, fails to encompass the heterogeneity of the disease. The COPD assessment test (CAT), a multi-dimensional, patient-filled questionnaire, assesses the overall health status of patients, and is recommended as part of the assessment of individuals with COPD. However, information regarding the range of values for the test in a non-COPD population (normative values) is limited, and consequently, knowledge regarding the optimal cut-off, and the minimum clinically important difference (MCID) for the test remain largely empirical. METHODS: CanCOLD is a population-based multi-center cohort study conducted across Canada, the methodology of which is based on the international BOLD initiative. The study includes subjects with COPD, at-risk individuals who smoke, and healthy control subjects. CAT questionnaires were administered at baseline to all subjects. Among non-COPD subjects, normative values for the CAT questionnaire, and psychometric properties of the test were characterized. Predictors of high CAT scores were identified using multivariable logistic regression. RESULTS: Of the 525 non-COPD subjects enrolled, 500 were included in the analysis. Mean FEV1/FVC ratio among the 500 included subjects was 0.77 (SD 0.49); the mean predicted FEV1 was 99.38% (SD 16.88%). The overall mean CAT score was 6 (SD 5.09); scores were higher among females (6.43, SD 5.59), and subjects over 80 years of age (mean 7.58, SD 6.82). Cronbach alpha for the CAT was 0.79, suggesting a high internal consistency for the test. A score of 16 was the 95th percentile for the population, and 27 subjects (5.4%) were found to have a CAT score > =16. Current smoking (aOR 3.41, 95% CI 1.05, 11.02), subject-reported physician-diagnosed asthma (aOR 7.59, 95% CI 2.71, 21.25) and musculoskeletal disease (aOR 4.09, 95% CI 1.72, 9.71) were found to be significantly associated with a score ≥16. CONCLUSIONS: The characterization of CAT scores in the general population will be useful for norm-based comparisons. Longitudinal follow-up of these subjects will help in the optimization of cut-offs for the test.