Chronic obstructive pulmonary disease in adults, 2012 to 2013
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Chronic obstructive pulmonary disease (COPD) is a condition characterized by a progressive and chronic airflow obstruction, shortness of breath, persistent wheezing and coughing, and sputum production that occurs primarily in adults over the age of 35. Chronic bronchitis and emphysema are the two most common forms of COPD and cigarette smoking is responsible for 80% to 90% of cases,Note 1 suggesting that the majority of COPD cases can be prevented. Other contributing factors may include outdoor, indoor and occupational air pollution.Note 2 Although airflow obstruction is not fully reversible, COPD can be treated and the symptoms controlled with proper medication and exercise programs.Note 3,Note 4
The Canadian Health Measures Survey (CHMS) used a health questionnaire to determine whether or not respondents were previously diagnosed with COPD by a health care professional (self-reported COPD). Among Canadians aged 35 to 79 years, 3% reported a diagnosis of COPD (Chart 1). Self-reported COPD diagnosis was not significantly different for men (4%) and women (3%). Older adults aged 60 to 79 years were significantly more likely to self-report a diagnosis of COPD (6%) compared to younger adults aged 35 to 59 years (2%) (Chart 1).
The CHMS also conducted a spirometry test to measure lung function (see About spirometry and COPD). The results indicate that 11% of Canadians aged 35 to 79 had a measured airflow obstruction consistent with COPD (Chart 1).Note 5 This is significantly different from the 3% who self-reported a diagnosis of COPD. There was also a significant difference between self-reported and measured COPD for men (4% compared to 9%), women (3% compared to 12%), and in the 35 to 59 age group (2% compared to 12%)(Chart 1).
The disparity of results between reported and measured COPD suggest that COPD is under-diagnosed in Canadian adults. Among the 11% of Canadians with measured airflow obstruction consistent with COPD, 90% did not report being previously diagnosed by a health care professional (Chart 2). This represents approximately 10% of the total population of Canadian adults aged 35 to 79. A small percentage of the population (3%) without measured COPD did self-report having been diagnosed by a health-care professional (data not shown). However, it could not be determined whether this was due to an over-diagnosis of COPD in the Canadian adult population, or due to the use of medication to control airflow obstruction.
About spirometryNote 6 and COPDNote 7,Note 8
Spirometry is a functional tool that measures the volume of air an individual inhales and exhales in addition to the speed at which the air is moved in or out of the lungs. In the same manner that blood pressure measurements provide important information about general cardiovascular health, spirometry is invaluable as a screening tool for general respiratory health. Used alongside other respiratory tests, spirometry allows medical practitioners to monitor respiratory health for conditions such as COPD. Spirometry results are interpreted by comparing measurements to the expected values for a normal healthy individual of the same sex and similar age with the same body dimensions and ethnic characteristics.
The spirometry measurements of primary interest for COPD diagnosis are:
- Forced vital capacity (FVC): the total volume of air that can be forcibly exhaled after a maximum inspiration.
- Forced expiratory volume in one second (FEV1): the volume of air that can be forcibly exhaled in the first second of a FVC manoeuvre.
- The FEV1 to FVC ratio (FEV1/FVC) is used as the value for diagnostic purposes.
Self-reported COPD was determined from the health questionnaire administered as part of the CHMS. Respondents were asked if they had ever been diagnosed with COPD by a health-care professional.
A measured COPD diagnosis was based on measured spirometry results, where the FEV1/FVC was below the lower limit of normal (LLN).Note 4 The LLN takes into account ethnicity, height, age and sex, and establishes a cut-off value for the FEV1/FVC below which 5% of healthy subjects fall.Note 7 This in turn is considered an abnormal value and is consistent with a diagnosis of COPD. In other words, 95% of the healthy population falls above this set value and are considered normal and not within the COPD guidelines. This approach allows for a more appropriate and accurate measure and diagnosis of COPD. However, it is important to note that asthma also causes a reduction in spirometry measurements but could not be separated for this report as a post-bronchodilator test was not administered. Previously released fact sheets on COPD by the CHMS used the Global Initiative for Chronic Obstructive Lung Disease (GOLD)Note 9 criteria to diagnose COPD. Due to this change, direct comparisons to previous released fact sheets are not possible.
Aggarwal, AN. 2008. “How appropriate is the gold standard for diagnosis of airway obstruction?” Lung India: official organ of Indian Chest Society, vol. 25.
Global Initiative for Chronic Obstructive Lung Disease (GOLD). 2010. Spirometry for Health Care Providers. www.goldcopd.org/uploads/users/files/GOLD_Spirometry_2010.pdf (accessed: July 3, 2014).
Hankinson, J.L., Odencrantz, J., and K. Fedan. 1999. “Spirometric Reference Values from a Sample of the General U.S. Population.” American Journal of Respiratory and Critical Care Medicine, vol. 159.
Health Canada. 2013.Respiratory Effects of Air Pollution. Ottawa. http://www.hc-sc.gc.ca/ewh-semt/air/out-ext/health-sante/respir-eng.php (accessed: August 12, 2014).
Miller, M.R., Hankinson, J., Brurasco, V., et al. 2005. Standardisation of spirometry. European Respiratory Journal, vol. 26, no. 2.
Public Health Agency of Canada. 2012. Chronic Pulmonary Obstructive Disease (COPD). Ottawa. http://www.phac-aspc.gc.ca/cd-mc/crd-mrc/copd-mpoc-eng.php (accessed: May 12, 2014).
Public Health Agency of Canada.2008. I have COPD. Why is it important for me to exercise? Ottawa. http://www.phac-aspc.gc.ca/cd-mc/crd-mrc/copd_exercise-mpoc_exercice-eng.php (accessed: May 12, 2014).
Swanney, M.P., Ruppel, G., Enright, P., et al. 2008. “Using the lower limit of normal for the FEV1/FVC ratio reduces the misclassification of airway obstruction.” Thorax, vol. 63.
The Lung Association. 2013. COPD. Ottawa. http://www.lung.ca/diseases-maladies/copd-mpoc/treatment-traitement/medications-medicaments_e.php (accessed: May 12, 2014).
Additional data from the Canadian Health Measures Survey are available from CANSIM tables 117-0001 to 117-0011.
For more information on the Canadian Health Measures Survey, please contact Statistics Canada's Statistical Information Service (toll-free 1-800-263-1136; 514-283-8300; email@example.com).
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