Investigators: Simon Bacon (PI), Kim Lavoie, Manon Labrecque, Catherine Lemière, Jean-Luc Malo, Denyse Gautrin, André Cartier, Blaine Ditto. Student: Maxine Boudreau (PhD student applicant); Partner: IRSST
Background: Asthma caused by sensitisation to agents encountered in the workplace affects approximately 10% of all cases of adult-onset asthma. The precise factors which contribute to the development of occupational asthma (OA) in some, but not all, exposed individuals remain unknown. Though some of these factors may be biological, those related to psychological factors remain virtually unexplored. There is consistent evidence of a relationship between acute daily stress and cardiovascular disease (CVD).1 In addition, we have previously shown that increased daily stress (higher levels of negative emotions, such as feeling sad, stressed, and angry) in CVD patients was associated with reduced high- and low-frequency power heart rate variability (HRV).2 These data suggest that self-reported stress during the day is associated with a reduction in parasympathetic control and an alteration in sympathetic control. There is growing evidence that acute stress and changes in the sympathetic nervous system (SNS) are associated with poorer immune profiles and potentially worse asthma symptoms.3,4 The extent to which acute daily stress influences OA and asthma-like symptoms at work is unknown. Objective and hypotheses: We plan to investigate the extent to which daily psychological stress influences the experience of asthma-like symptoms (e.g., wheezing) and lung function (daily peak expiratory flow variability), and the mechanistic role the SNS plays in these relationships. It is hypothesised that an increase in negative emotions will precede the experience of asthma-like symptoms and a reduction in lung function. It is also hypothesised that this relationship will be mediated by alterations in parasympathetic and sympathetic control.
Methods: A total of 20 participants with suspected (but not confirmed) OA, who exhibit work-related asthma symptoms on 3-5 days per week will be recruited. Patients with a previous diagnosis of non-occupational (“regular/personal”) asthma will be excluded. Patients will be given a self-report diary, ambulatory peak flow meter (Piko1), and a pre-programmed electronic pager for 5 days (3 work days and 2 non-work days). Every 30 minutes during waking hours, participants will be prompted (by the pager) to make a diary recording, indicating the time, their location, their posture, the activity they are undertaking, and a series of emotional measures. Using a standard Likert scale, participants will indicate their level of the following emotional states; anger, stress, sadness, relaxed, happy, and tired. In addition, when patients experience an asthma-like event (e.g., wheezing, shortness of breath) they will also be asked to indicate in the diary the time, nature, and severity of the event. The use of this kind of diary has been widely validated in the CVD literature.5 Peak flow measures will be taken 4 times a day (waking, lunch, dinner, and prior to go to bed). HRV data will be collected using the Polar S810i R-R monitor. Participants will be instrumented with the monitor at the start of each of their shifts and then at the end of the shift participants will return the monitor. We will conduct a series of random-effect models to assess: 1) the impact of daily stress on asthma symptoms; 2) the effects of daily stress on peak flow; and 3) the impact of alterations in high-frequency and low-frequency HRV on asthma symptoms. Pertinence and originality: This will be the first study to evaluate the influence of daily psychological stress on asthma-like symptoms and peak flow in the work place. In addition, the joint influence of autonomic and sympathetic tone on asthma-like symptoms will be assessed as a possible mechanism of the relationship. The results could lead to greater understanding of the potential moderating effects of stress on the development of OA, and to greater recognition of how psychological stress in the workplace is an important risk factor in this population. Budget: A total of $20,000 is requested for nurse assistance with data collection and study materials ($18,000) and for subject payment ($100 per subject = $2,000).
1. Rozanski et al. The epidemiology, pathophysiology, and management of psychosocial risk factors in cardiac practice. JACC 2005;45:637. 2. Bacon et al. Effects of daily stress on autonomic cardiac control in patients with coronary artery disease. Am J Cardiol 2004;93:1292. 3. Lehrer. Emotionally-triggered asthma: a review of research literature and some hypotheses for self-regulation therapies. Appl Psychophysiol Biofeedback 1998;23:13-41. 4. Miller. The autonomic nervous system (ANS) dysregulation model of the influence of emotions in asthma. Psychosom Med 2001;63:112. 5. Gullette et al. Effects of mental stress on myocardial ischemia during daily life. JAMA 1997;277:1521.