Relationship between self-reported odor intolerance and sensitivity to inhaled capsaicin: proposed definition of airway sensory hyperreactivity and estimation of its prevalence.

STUDY OBJECTIVES: The aim of this study was to investigate the relationship between the behavioral consequences of self-reported odor sensitivity with the chemical sensitivity scale for sensory hyperreactivity (CSS-SHR) and cough sensitivity to inhaled capsaicin. We also wanted to estimate the prevalence of airway sensory hyperreactivity (SHR), which was defined as a positive CSS-SHR score in combination with a positive capsaicin inhalation test result.

DESIGN: A general population-based study with randomly selected individuals after stratification for age and gender.

SETTING: Skövde Central Hospital, Departments of Lung Medicine and Otorhinolaryngology, Sweden.

PARTICIPANTS: A total of 693 randomly selected individuals from a population-based study in which 595 persons (86%) responded to the CSS-SHR questionnaire.

INTERVENTIONS: The individuals were divided into four groups with different odor sensitivity according to their CSS-SHR score. Of these, 137 individuals were randomly recruited for the capsaicin inhalation test. Capsaicin inhalation was performed with concentrations of 0.4 and 2.0 mumol/L in a randomized order. The number of coughs were registered and counted for 10 min from the start of each inhalation.

MEASUREMENTS AND RESULTS: Of the 137 individuals who were recruited for the capsaicin inhalation test, 103 (75%) participated. Sixteen individuals had increased cough sensitivity and fulfilled the criteria for a positive capsaicin inhalation test result. Of the individuals with a positive capsaicin inhalation test result, > 80% also had a positive CSS-SHR score. Only 5% of the individuals with a negative CSS-SHR score had a positive capsaicin inhalation test result. The order of inhaled capsaicin concentration was found to influence the results. The prevalence of SHR with the definition given above was estimated to be 6.3% in this general population.

CONCLUSIONS: A high CSS-SHR score was found to be directly related to the sensitivity for inhaled capsaicin, which made it possible to relate subjective data to objective findings.