The Effect of Odors on Asthma Symptoms

Not Applicable

• Conditions: Asthma
• Interventions: Behavioral: Therapeutic Suggestion; Behavioral: Asthmogenic Suggestion; Other: Phenylethyl Alcohol odor

• Registration Number: NCT02624362
• Lead Sponsor: Universitaire Ziekenhuizen KU Leuven

Brief Summary

An extended replication of Jaen \& Dalton (2014), the investigators aim to investigate the role of odors and associated trigger beliefs on symptom perception and airway inflammation in individuals with asthma

Detailed Description

Participants with asthma are randomly assigned to a 15-min (phenylethyl alcohol) odor inhalation, accompanied by either an asthmogenic suggestion (nocebo), or a therapeutic suggestion (placebo). Airway inflammation, lung function, and asthma symptoms are measured in response to the odor/suggestion, up to 24 hours after odor inhalation. The investigators are also measuring worry and heart rate variability as potential mediators of the response.

Study Timeline

• Study Start: 2015-08
• Study First Submitted: 2015-12-01
• Study First Submitted QC: 2015-12-07
• Study First Posted: 2015-12-08
• Status Verified: 2024-07
• Last Update Submitted: 2024-07-02
• Last Update Posted: 2024-07-03
• Primary Completion: 2026-07
• Study Completion: 2026-12

Recruitment & Eligibility

• Status: ENROLLING_BY_INVITATION
• Sex: All
• Target Recruitment: 48

Inclusion Criteria

• A physician diagnosis of asthma

Exclusion Criteria

• FEV1 lower than 60% predicted
• clinical condition other than asthma

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Odor+ Positive belief	Phenylethyl Alcohol odor	Participants receive 15 minute odor presentation (Phenylethyl Alcohol odor) accompanied by the suggestion that this odor improves asthma symptoms (therapeutic suggestion)
Odor+ Positive belief	Therapeutic Suggestion	Participants receive 15 minute odor presentation (Phenylethyl Alcohol odor) accompanied by the suggestion that this odor improves asthma symptoms (therapeutic suggestion)
Odor + Negative belief	Asthmogenic Suggestion	Participants receive 15 minute odor presentation (Phenylethyl Alcohol odor) accompanied by the suggestion that this odor worsens asthma symptoms (asthmogenic suggestion)
Odor + Negative belief	Phenylethyl Alcohol odor	Participants receive 15 minute odor presentation (Phenylethyl Alcohol odor) accompanied by the suggestion that this odor worsens asthma symptoms (asthmogenic suggestion)

Primary Outcome Measures

Name	Time	Method
Change from Baseline Exhaled Nitric Oxide to 24 hours after odor induction	baseline, immediately after odor induction, 2 hours after odor induction, 24 hours after odor induction	Fraction of exhaled nitric oxide

Secondary Outcome Measures

Name	Time	Method
Cortisol	baseline, immediately after odor induction, 2 hours after odor induction, at awakening, 30 min after awakening, 24 hours after odor induction	cortisol awakening response (AUC), and changes in cortisol (AUC) will be measured using saliva sampling
asthma symptoms	baseline, immediately after odor induction, 2 hours after odor induction, 24 hours after odor induction	measured using the Asthma Symptom Checklist
Forced Expiratory Volume at one second (FEV1)	baseline, immediately after odor induction, 2 hours after odor induction, 24 hours after odor induction	Measured using Jaeger Masterscreen Spirometer, according to ERS-ATS guidelines
Change in Heart rate and Heart Rate Variability (HRV)	change from baseline to 24 hours after odor induction	24 hour heart rate data will be recorded using an ambulatory ECG monitor, and analyzed in 1 hour epochs, extracting mean of successive differences (MSD) as a variable of interest.
Worry	baseline, immediately after odor induction, 2 hours after odor induction, 24 hours after odor induction	measured using worry Visual Analog Scales
change in Fraction of end-tidal carbon dioxide (FetCO2)	change from baseline to 15 min odor presentation	FetCO2 (plateau %CO2 in exhaled air) is recorded continuously, and changes between baseline and odor presentation periods will be analysed
Change in Respiratory rate	change from baseline to 15 min odor presentation	respiratory rate (breaths/min) is recorded continuously, and changes between baseline and odor presentation periods will be analysed

Trial Locations

Locations (1)

UZ Leuven; 🇧🇪 Leuven, Belgium