Factors influencing the occurrence of airway hyperreactivity in the general population: The importance of atopy and airway calibre. European Respiratory Journal, 7, 881-887

Respiratory Medicine Unit, City Hospital, Nottingham, UK.
European Respiratory Journal (Impact Factor: 7.64). 06/1994; 7(5):881-7.
Source: PubMed


The factors that determine the occurrence of airway hyperreactivity in the general population are not clearly understood. This study was designed to assess the independent effects of age, atopy, smoking and airway calibre. In a random sample of 2,415 adults aged 18-70 yrs we measured reactivity to methacholine as the dose provoking a 20% fall (PD20) in one-second forced expiratory volume (FEV1), atopy as the mean skin wheal response to three common environmental allergens, and airway calibre as the baseline FEV1 in absolute terms, as percent predicted (FEV1 % predicted) and as percent forced vital capacity (FEV1 % FVC). Hyperreactivity, defined as a PD20 < or = 12.25 mumol, was present in 314 (13%) of the sample, and before adjustment for FEV1 was more common in females (independent odds ratio (OR) = 2.05 (95% confidence interval 1.6-2.7)), current smokers (OR = 1.89 (1.3-2.6)), atopics (OR = 1.39 (1.3-1.5) per mm skin wheal), and in older age groups (OR for age 60-70 yrs relative to 18-29 yrs = 2.70 (1.7-4.3)). However, the odds of hyperreactivity were also strongly and independently related to absolute FEV1 (OR = 0.46 (0.27-0.77) per litre), FEV1 % predicted (OR = 0.96 (0.94-0.98) per percent), and FEV1 % FVC (OR = 0.92 (0.90-0.94) per percent; combined chi-square on 3 df = 312, p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

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    • "It is not clear why these subjects respond however , it is possible that either one of or both the variable and fixed components may be present. There is evidence that reduced airway caliber may be a predictor of the response (Britton et al., 1994; Litonjua et al., 1999; Parker and McCool, 2002; Parker et al., 2003). "
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    ABSTRACT: Airway hyperresponsiveness (AHR) and airway inflammation are key pathophysiological features of asthma. Bronchial provocation tests (BPTs) are objective tests for AHR that are clinically useful to aid in the diagnosis of asthma in both adults and children. BPTs can be either "direct" or "indirect," referring to the mechanism by which a stimulus mediates bronchoconstriction. Direct BPTs refer to the administration of pharmacological agonist (e.g., methacholine or histamine) that act on specific receptors on the airway smooth muscle. Airway inflammation and/or airway remodeling may be key determinants of the response to direct stimuli. Indirect BPTs are those in which the stimulus causes the release of mediators of bronchoconstriction from inflammatory cells (e.g., exercise, allergen, mannitol). Airway sensitivity to indirect stimuli is dependent upon the presence of inflammation (e.g., mast cells, eosinophils), which responds to treatment with inhaled corticosteroids (ICS). Thus, there is a stronger relationship between indices of steroid-sensitive inflammation (e.g., sputum eosinophils, fraction of exhaled nitric oxide) and airway sensitivity to indirect compared to direct stimuli. Regular treatment with ICS does not result in the complete inhibition of responsiveness to direct stimuli. AHR to indirect stimuli identifies individuals that are highly likely to have a clinical improvement with ICS therapy in association with an inhibition of airway sensitivity following weeks to months of treatment with ICS. To comprehend the clinical utility of direct or indirect stimuli in either diagnosis of asthma or monitoring of therapeutic intervention requires an understanding of the underlying pathophysiology of AHR and mechanisms of action of both stimuli.
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    • "Allergen sensitization has been associated with asthma in older adults (Litonjua et al. 1997; Weiss et al. 1998). Older adults have smaller airways compared with young adults, and this makes bronchial hyperresponsiveness more likely (Britton et al. 1994; Peat et al. 1992). "
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    ABSTRACT: Relative to research on effects of environmental exposures on exacerbation of existing asthma, little research on incident asthma and environmental exposures has been conducted. However, this research is needed to better devise strategies for the prevention of asthma. The U.S. Environmental Protection Agency (EPA) and National Institute of Environmental Health Sciences held a conference in October 2004 to collaboratively discuss a future research agenda in this area. The first three articles in this mini-monograph summarize the discussion on potential putative environmental exposure; they include an overview of asthma and conclusions of the workshop participants with respect to public health actions that could currently be applied to the problem and research needs to better understand and control the induction and incidence of asthma, the potential role of indoor/outdoor air pollutants in the induction of asthma), and biologics in the induction of asthma. Susceptibility is a key concept in the U.S. EPA "Asthma Research Strategy" document and is associated with the U.S. EPA framework of protecting vulnerable populations from potentially harmful environmental exposures. Genetics, age, and lifestyle (obesity, diet) are major susceptibility factors in the induction of asthma and can interact with environmental exposures either synergistically or antagonistically. Therefore, in this fourth and last article we consider a number of "susceptibility factors" that potentially influence the asthmatic response to environmental exposures and propose a framework for developing research hypotheses regarding the effects of environmental exposures on asthma incidence and induction.
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    ABSTRACT: House dust mites (HDM) are one of the major risk factors for the development of bronchial asthma. The percentage of sensitization to HDM was reported to be 71.9% in Taipei City. In southwestern Taiwan, the percentage of sensitization to HDM has not been estimated. We retrospectively reviewed the medical records of asthmatic patients treated at the Chiayi branch of Chang Gung Memorial Hospital to investigate the percentage and associations with demographic characteristics. We analyzed the data of 194 asthmatic patients diagnosed between January 2003 and July 2005. Sensitization to indoor allergens was identified by serum specific immunoglobulin E (IgE) of ImmunoCAP. Demographic characteristics of age, gender and residence were evaluated for associations with allergic sensitization. The percentage of sensitization to HDM was only 45.9% in patients in southwestern Taiwan. The majority of the studied group were elderly patients. The age variable significantly influenced the percentage of sensitization to HDM and cockroaches (p < 0.001 in both comparisons). The gender variable contributed to sensitization to cockroaches only (p = 0.002). For residential variables, there was no significant difference in the percentage of allergic sensitization to all tested indoor allergens among distinct areas of southwestern Taiwan. The percentage of sensitization to HDM in asthmatic patients residing in southwestern Taiwan was lower than that in metropolitan patients. This discrepancy might be attributed to the larger proportion of aged patients.
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