Prevalence and Sex-Specific Risk Factors for Asthma-COPD Overlap among Middle-Aged and Older Canadians

  • Author / Creator
    Veerasingam, Edwina
  • Background: Asthma and chronic obstructive pulmonary disease (COPD) are major public health concerns and are among the most prevalent chronic respiratory diseases worldwide. However, a subset of patients presents with clinical features of both asthma and COPD, and recently, the term asthma-COPD overlap (ACO) was proposed to recognize this subset of patients. Studies show that individuals with ACO are more likely to experience a poorer quality of life, rapid disease progression, more frequent respiratory exacerbations, rapid decline in lung function, higher mortality, and greater healthcare utilization than patients with COPD or asthma alone. ACO disproportionately burdens females, and many epidemiological studies have reported a growing increase in ACO and COPD prevalence and mortality rates among females. Despite this, sex-specific differences and the role that sex and gender play in driving these disparities are not fully understood. This analysis aims to identify male and female-specific factors associated with ACO, COPD, and asthma. This study analyzed the baseline data from the Canadian Longitudinal Study on Aging (CLSA), a large population-based, prospective cohort study on middle-aged and older Canadian adults. The study cohort comprised of 30,097 adults between the ages of 45 and 85 years that participated in an in-home interview and a data collection site visit for physical assessment, blood, and urine sample collection.
    Methods: Participants were categorized into four groups (control, asthma-COPD overlap (ACO), COPD only, and asthma only) based on self-reported response to the survey questions “has a doctor ever told you had asthma?” and “has a doctor told you that you have/had any of the following: emphysema, chronic bronchitis, chronic obstructive pulmonary disease (COPD), or chronic changes in lungs due to smoking?”. ACO was defined as a positive response to both questions. Environmental data collected by the Canadian Urban Environmental Health Research Consortium (CANUE) was linked to participant’s reported postal code at the time of recruitment. The linked CANUE data includes annual average concentration exposure estimates for sulfur dioxide, nitrogen dioxide, ozone, and fine particulate matter. Multinomial logistic regression was used to identify significant male- and female-specific social, physical, and environmental predictors for ACO, COPD, and asthma in the multivariable analysis.
    Results: The prevalence of ACO, COPD, and asthma was significantly greater in females than males (ACO: 2.17% vs. 1.41%; COPD: 3.22% vs. 2.87%; asthma: 13.31% vs. 10.11%). In the multivariable analysis, Aboriginal ethnicity, smoking, and lower education were significantly associated with obstructive lung disease for both males and females. In addition, marital status, province, age, and obesity were associated with asthma, COPD, or ACO among females but not males. While for males, unemployment was a significant factor for obstructive lung disease, which was not significant in females. Unemployed males had 2.60 times the likelihood of reporting ACO, and 2.23 times the likelihood of reporting COPD compared to employed males. Males with ACO and COPD had more severe lung obstruction than females. Subjects with ACO or COPD had more comorbidities, respiratory symptoms and were more likely to rate their health as “poor” than subjects with asthma or no respiratory symptom. Depression was the most commonly reported comorbidity for participants with ACO, irrespective of sex. Female subjects who were obese were 2.58 times more likely to develop ACO than females in the normal/underweight category. Participants with ACO were more likely to have hypothyroidism, and the proportion was higher among females. Hypothyroidism was not significantly related to COPD for males or females. Males with ACO were more likely to report having coughing and coughing with phlegm symptoms than females, and females with ACO were more likely than males to report shortness of breath and wheeze. No statistically significant associations were observed between environmental exposure and respiratory outcomes for females. However, nitrogen dioxide was associated with an increased risk of asthma among males.
    Conclusions: In the Canadian adult population, the prevalence of asthma, COPD, and ACO was greater among females than males. Risk factors for ACO varied between males and females. This study provides important and novel information to guide future research and development of public health programs to address the disproportionate burden of ACO and COPD mortality and morbidity among females in Canada.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.