Estimating the prevalence of COPD in Canada: Reported diagnosis versus measured airflow obstruction.

BACKGROUND: Estimates of chronic obstructive pulmonary disease (COPD) prevalence based on self-reports of a diagnosis are thought to underestimate the prevalence of COPD in Canada. DATA AND METHODS: Pre-bronchodilator spirometry measures were obtained from the 2007 to 2009 Canadian Health Measures Survey for 2,487 individuals aged 35 to 79. The prevalence of self-reported chronic bronchitis symptoms and self-reported diagnosis of COPD by a health care professional was compared with the prevalence of measured airflow obstruction according to seven definitions, including the Global Initiative for Obstructive Lung Disease (GOLD) criteria. RESULTS: The prevalence of measured airflow obstruction compatible with COPD was two to six times greater than estimates based on self-reports of a diagnosis. An estimated 16.6% (95% CI: 14.3%-18.9%) of people aged 35 to 79 had pre-bronchodilator airflow obstruction as defined by ≥ GOLD stage I, and 8.1% (95% CI: 6.0%-10.2%) had ≥ GOLD stage II. INTERPRETATION: This study suggests that the prevalence of COPD in Canada has been underestimated.

Geographic and gender variability in the prevalence of bronchial responsiveness in Canada.

OBJECTIVES: Geographic variability in reported prevalences of asthma worldwide could in part relate to interpretation of symptoms and diagnostic biases. Bronchial responsiveness measurements provide objective evidence of a common physiologic characteristic of asthma. We measured bronchial responsiveness using the standardized protocol of the European Community Respiratory Health Survey (ECRHS) in six sites in Canada, and compared prevalences across Canada with international sites. DESIGN: Samples of 3,000 to 4,000 adults aged 20 to 44 years were randomly selected in Vancouver, Winnipeg, Hamilton, Montreal, Halifax, and Prince Edward Island, and a mail questionnaire was completed by 18,616 individuals (86.5%). Preselected random subsamples (n = 2,962) attended a research laboratory for examination including more detailed questionnaires, lung function testing including methacholine challenge, and skin testing with 14 allergens. RESULTS: Prevalences of bronchial hyperresponsiveness, measured as cumulative dose of methacholine required to produce a 20% fall from the post-saline solution FEV1 < or = 1 mg, ranged from 4.9% (95% confidence interval [CI], 1.6 to 8.5) in Halifax to 22.0% (95% CI, 18.1 to 26.0) in Hamilton (median, 10.7%). In all Canadian sites, bronchial hyperresponsiveness was more prevalent in women than in men. Neither the geographic nor gender differences were accounted for by differences in age, smoking, skin test reactivity, or baseline FEV1. Geographic- and gender-related variability changed little when only bronchial hyperresponsiveness associated with asthma-like symptoms was considered. CONCLUSIONS: A wide variability in bronchial responsiveness can occur within one country, almost as wide as the range found across all international sites participating in the ECRHS study and not explained by differences in gender, smoking, skin test reactivity, and FEV1. While gender variability in the prevalence of bronchial responsiveness is likely due to hormonal and immunologic factors, geographic variability is likely to result from environmental factors.

Are questionnaires on respiratory symptoms reliable predictors of airway hyperresponsiveness in athletes and sedentary subjects?

This study aimed at determining the frequency of respiratory symptoms in high-level athletes and whether respiratory questionnaires are reliable predictors of airway hyperresponsiveness (AHR) in this population compared with control subjects. One hundred high-level athletes exercising in different conditions of ambient air (dry, humid, cold or mixed dry and humid) and 50 sedentary control subjects answered four question sets on exercise-induced symptoms of postnasal drip (Q1), breathlessness, chest tightness and wheezing (Q2), and cough (Q3). Another question set (Q4) evaluated the self-description of nociceptive sensations associated with respiratory symptoms. Methacholine inhalation tests were performed in all subjects to obtain a 20% fall in forced expiratory volume in 1 second (PC20). AHR could be detected by questionnaires in 37 of 44 (84%) subjects with a PC20 < 8 mg/mL. Sensitivity to detect AHR varied between the different subgroups of athletes with each of the question sets; however, no significant differences in sensitivity were observed between the groups of athletes and controls except for Q3 (P=.007), in which athletes exercising in cold air reported more exercise-induced cough. Q2 had a better specificity (83%) than Q3 (77%) and Q4 (64%). Combined question sets revealed that three swimmers, two triathletes, and two controls, who answered negatively to all question sets, had a PC20 < 8 mg/mL. Questionnaires on symptoms and on associated nociceptive sensations may help to detect AHR as well in athletes and controls, although for some subgroups of athletes such as swimmers and triathletes and in some controls, false negative questionnaires can be observed and AHR underreported.