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Vascular Risk Associated with Asthma
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- Author / Creator
- Henry, Shelby
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Background and Rationale
Asthma is a chronic inflammatory disease of the airways characterized by episodic bronchoconstriction and airway hyper-responsiveness resulting in symptoms such as coughing, wheezing, and shortness of breath. Asthma is one of the most common chronic diseases in the world, effecting an estimated 300 million people. Previous research has demonstrated that individuals with asthma have an increased risk for cardiovascular morbidity and mortality, however the reason for this is unknown. Systemic inflammation, arterial stiffness and vascular dysfunction are independent predictors of cardiovascular risk in health and in disease, all of which have been reported to be abnormal in people with asthma. Approximately 25-35% of people with a physician diagnosis of asthma do not demonstrate asthma with physiological testing. It is unclear if the increased cardiovascular risk reported in people with asthma is observed in those with an asthma diagnosis that cannot be confirmed by physiological testing.Purpose and Hypothesis
The purpose of this study was to determine if individuals with an asthma diagnosis that cannot be confirmed by physiological testing demonstrate vascular function, arterial stiffness and systemic inflammation similar to individuals with an asthma diagnosis that is confirmed by physiological testing. Additionally, a group of healthy controls were recruited for further comparison. It was hypothesized that individuals with a physician diagnosis of asthma, but no evidence of asthma with physiological testing would have similar vascular function, arterial stiffness and systemic inflammation compared to those with asthma confirmed by physiological testing.Methods
Individuals aged 18-55 years with confirmed asthma (n=15), individuals with an asthma diagnosis that cannot be confirmed by physiological testing (n=12), as well as healthy controls (n=13) were recruited for this cohort study. Ultrasound imaging of the brachial artery (FMD) and carotid-radial pulse wave velocity (crPWV) were obtained to assess vascular function and arterial stiffness, respectively. A venous blood sample was acquired for analysis of systemic inflammation (CRP), and a Fitbit was worn for seven days to determine physical activity and reported in average steps per day. All participants completed a full pulmonary function test including spirometry before and after administration of 400µg of salbutamol to assess lung function and presence of reversible airway obstruction. When appropriate, participants completed an exercise challenge as well as a methacholine challenge to objectively confirm an asthma diagnosis.Results
When comparing the confirmed asthma group to the unconfirmed asthma group, there were no differences found in FMD (confirmed: 7.99 ± 2.70%, unconfirmed: 7.59 ± 2.94%, p=0.72), crPWV (confirmed: 8.33 ± 1.42 m/s, unconfirmed: 8.60 ± 0.97 m/s, p=0.60), or CRP (confirmed: 3.53 ± 2.90 mg/L, unconfirmed: 3.77 ± 1.78 mg/L, p=0.81).
As both asthma groups demonstrated no clinically or statistically significant differences, they were combined and compared to healthy controls. A trend was observed with FMD between groups, with the asthma group demonstrating lower FMD compared to healthy controls (7.81 ± 2.76%, 9.48 ± 2.55%, p=0.08). There were no differences in crPWV (asthma: 8.47 ± 1.20 m/s, control: 8.00 ± 1.64 m/s, p=0.33), or CRP (asthma: 3.64 ± 2.40 mg/L, control: 4.45 ± 3.37 mg/L, p=0.43) observed between groups. Participants with asthma who used any asthma medication tended to have lower vascular function compared to those using no asthma medication (any: 7.37 ± 2.59% vs. no: 9.75 ± 2.90%, p= 0.08). Additionally, the participants with asthma tended to be less physically active, measured in average steps per day, compared to healthy controls (p=0.05).Discussion and Significance
The unconfirmed and confirmed asthma groups demonstrated similar FMD, and when combined, tended to have lower FMD compared to healthy controls. The results of this study suggest that objective confirmation of asthma alone is not an important determinant of cardiovascular risk. Rather, other factors associated with a physician diagnosis/clinical history of asthma, such as asthma medication use and physical inactivity, may be more important determinants of cardiovascular risk in people with asthma. It is critical to obtain an objective diagnosis of asthma through physiological testing prior to beginning treatment in order to reduce the unnecessary use of asthma medication. More research is needed to further understand the association of asthma medication use (both medication type and dose) and physical inactivity to the increased cardiovascular risk reported in people with asthma. -
- Graduation date
- Fall 2019
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.