Changes in bronchial responsiveness to inhaled histamine over four years in middle aged male smokers and ex-smokers

Systematic review of the evidence relating FEV1 decline to giving up smoking

BACKGROUND

The rate of forced expiratory volume in 1 second (FEV1) decline ("beta") is a marker of chronic obstructive pulmonary disease risk. The reduction in beta after quitting smoking is an upper limit for the reduction achievable from switching to novel nicotine delivery products. We review available evidence to estimate this reduction and quantify the relationship of smoking to beta.

METHODS

Studies were identified, in healthy individuals or patients with respiratory disease, that provided data on beta over at least 2 years of follow-up, separately for those who gave up smoking and other smoking groups. Publications to June 2010 were considered. Independent beta estimates were derived for four main smoking groups: never smokers, ex-smokers (before baseline), quitters (during follow-up) and continuing smokers. Unweighted and inverse variance-weighted regression analyses compared betas in the smoking groups, and in continuing smokers by amount smoked, and estimated whether beta or beta differences between smoking groups varied by age, sex and other factors.

RESULTS

Forty-seven studies had relevant data, 28 for both sexes and 19 for males. Sixteen studies started before 1970. Mean follow-up was 11 years. On the basis of weighted analysis of 303 betas for the four smoking groups, never smokers had a beta 10.8 mL/yr (95% confidence interval (CI), 8.9 to 12.8) less than continuing smokers. Betas for ex-smokers were 12.4 mL/yr (95% CI, 10.1 to 14.7) less than for continuing smokers, and for quitters, 8.5 mL/yr (95% CI, 5.6 to 11.4) less. These betas were similar to that for never smokers. In continuing smokers, beta increased 0.33 mL/yr per cigarette/day. Beta differences between continuing smokers and those who gave up were greater in patients with respiratory disease or with reduced baseline lung function, but were not clearly related to age or sex.

CONCLUSION

The available data have numerous limitations, but clearly show that continuing smokers have a beta that is dose-related and over 10 mL/yr greater than in never smokers, ex-smokers or quitters. The greater decline in those with respiratory disease or reduced lung function is consistent with some smokers having a more rapid rate of FEV1 decline. These results help in designing studies comparing continuing smokers of conventional cigarettes and switchers to novel products.

Changes in airway hyperresponsiveness following smoking cessation: comparisons between Mch and AMP

BACKGROUND

Given the observed association between smoking, inflammation and airway hyperresponsiveness (AHR) one may predict that smoking cessation may improve AHR. However, only a few studies have investigated the effect of smoking on AHR and their results appear to be conflicting depending on the stimulus used in their bronchoprovocation protocol. The aim of the current study was to compare changes in AHR between direct (methacholine (Mch)) and indirect (adenosine 5'monophosphate (AMP)) stimuli before and at different time points after smoking cessation in smokers with allergic rhinitis (+/-asthma).

METHODS

We have prospectively studied changes in AHR to inhaled Mch and AMP in smokers with allergic rhinitis (+/-asthma), before and at 6 and 12 months after smoking cessation.

RESULTS

It was found that 28% (16/57) of the participants had quit smoking by the end of the study. No significant change in AHR was observed in smoking cessation failures. A significant improvement in AHR to AMP but not Mch was observed 6 months after smoking cessation in quitters; a 1.2 doubling concentrations change in PC20 AMP was measured whereas only a 0.4 doubling concentrations change was observed for PC20 Mch. However, after 12 months smoking cessation the improvement in AHR became significant for both AMP and Mch, their dose-response curves being displaced to the right to a similar extent (1.4 and 1.1 doubling concentrations for AMP and Mch, respectively).

CONCLUSION

Smoking cessation can improve AHR in smokers who quit with a 6 months improvement being reported for the airways response to AMP but not Mch. AMP challenge may detect earlier changes in AHR in smokers during smoking cessation.

Airway reactivity to inhaled mannitol in cigarette smokers: a longitudinal study

Smoking induces airway hyperresponsiveness (AHR). Bronchial provocation with mannitol is used to identify AHR in subjects with asthma. This study aimed to determine the prevalence of airway hyperresponsiveness to mannitol in asymptomatic smokers compared to non-smokers and to assess if airway responsiveness to mannitol changes after smoking cessation. Airway responsiveness to inhaled mannitol was measured in smokers (n=42), and non-smokers (n=45). In smokers, the mannitol test was repeated 3 months after smoking cessation. Demographics including age, lung function and atopy status were similar for smokers and non-smokers (p=ns). Compared with non-smokers (2.2%), AHR to mannitol expressed by 15%> or = fall in FEV(1) was significantly more common in smokers (26.2%) (p=0.001). The provoking dose to induce a 15%> or = fall in FEV(1) (PD(15)), a measure of sensitivity, was median [IQR] 291 mg [207-377] in the 11 positive smokers. The response-dose ratio (RDR) (% fall in FEV(1)/cumulative dose), a measure of reactivity, was significantly higher in smokers (0.013 [0.006-0.029]) compared with non-smokers (0.004 [0.002-0.007]), (p<0.0001). After successful smoking cessation, the RDR decreased in most cases (p=0.01) and only one patient still recorded a 15% fall in FEV(1). None of the patients with a negative mannitol test turned positive, irrespective of the outcome of smoking cessation. AHR to mannitol is quite common in smokers compared to non-smokers and decreases significantly after smoking cessation. Thus, the mannitol test may be sensitive to non-asthmatic inflammation of the airways.

An Increase in Bronchial Responsiveness Is Associated with Continuing or Restarting Smoking

RATIONALE

Bronchial responsiveness (BHR) has been found to be associated with smoking, atopy, and lower lung function in cross-sectional studies, but there is little information on determinants of change in adults.

OBJECTIVES

To analyze change in bronchial responsiveness in an international longitudinal community study.

METHODS

The study was performed in 3,993 participants in the European Community Respiratory Health Survey who had bronchial responsiveness measured in 1991-1993, when aged 20 to 44 yr, and in 1998-2002.

MEASUREMENTS

Bronchial responsiveness was assessed by methacholine challenge. Serum samples were tested for total IgE, and for specific IgE to four common allergens. Smoking information was obtained from detailed administered questionnaires. Change in bronchial responsiveness was analyzed by change in IgE sensitization, smoking, and lung function, with tests of interaction terms with age and sex.

MAIN RESULTS

Continuing and restarting smokers had increasing bronchial responsiveness, approximately equivalent to a mean reduction in PD20 of 0.68 and 0.75 doubling doses, respectively, over 10 yr, in addition to a small increase explained by decline in FEV1. No other risk factor for change in bronchial responsiveness was identified.

CONCLUSIONS

Smoking is a risk factor for increasing bronchial responsiveness over and above the effect of decreasing lung function. Neither baseline IgE sensitization nor change in sensitization was shown to be a risk factor for increasing BHR, the latter possibly due to little overall increase or decrease in sensitization.

Does bronchial hyperresponsiveness in asthma matter?

Bronchial hyperresponsiveness is a fundamental component of the asthmatic inflammatory process causing airway narrowing on exposure to a bronchoconstrictor stimulus. This in turn causes patients to experience symptoms of breathlessness, chest tightness, cough and wheeze. Bronchial challenge tests can be performed in the laboratory to establish the degree of bronchial hyperresponsiveness to both direct and indirect stimuli. The extent to which asthma pharmacotherapy attenuates bronchial hyperresponsiveness is therefore an important measure of efficacy. This review article discusses the effects of inhaled and oral asthma treatment upon bronchial hyperresponsiveness and highlights how, in conjunction with conventional measures of asthma control, it can be used as an aid to optimally manage patients.

Methods for "indirect" challenge tests including exercise, eucapnic voluntary hyperpnea, and hypertonic aerosols

Bronchial provocation tests that use stimuli that act indirectly to cause airway narrowing have a high specificity for identifying people with active asthma who have the potential to respond to treatment with antiinflammatory drugs. The first test to be developed was exercise and it was used to assess the efficacy of drugs such as sodium cromoglycate. Eucapnic voluntary hyperpnea was developed later, as a surrogate test for exercise. Hypertonic aerosols were introduced to mimic the dehydrating effects of evaporative water loss that occurs during hyperpnea. A wet aerosol of 4.5% saline or a dry powder formulation of mannitol is used. At present the indirect challenge tests are becoming increasingly recognised as appropriate for monitoring treatment with inhaled steroids. Indirect tests identify those with potential for exercise-induced bronchoconstriction, an important problem for some occupations, such as the defence forces, fire fighters and the police force and for some athletic activities. The advantage in using an indirect challenges, over a direct challenge with a single pharmacological agonist, is that a positive response indicates that inflammatory cells and their mediators (prostaglandins, leukotrienes and histamine) are present in the airways in sufficient numbers and concentration to indicate that asthma is active at the time of testing. The corollary to this is that a negative test in a known asthmatic indicates good control or mild disease. Another advantage is that healthy subjects do not have significant airway narrowing to indirect challenge tests. The protocols used for challenge with indirectly acting stimuli are presented in detail.

Use of aerosols for bronchial provocation testing in the laboratory: where we have been and where we are going

Bronchial provocation testing with pharmacological agents that act directly on airway smooth muscle has important limitations. These include the inability to identify exercise-induced asthma (EIA), to differentiate the airway hyperresponsiveness (AHR) of airway remodelling from the AHR of active inflammation and to differentiate between doses of steroids. Recent studies show that tests that act indirectly to narrow airways are more sensitive than pharmacological agents for identifying airway inflammation and response to treatment. Adenosine monophosphate (AMP) is an indirect challenge that acts on mast cells to cause release of mediators. Hypertonic saline is another and, since its development in the 1980s, has become widely used in Australia. Hypertonic (4.5%) saline is used to identify those with active asthma, those with EIA and those who wish to enter certain occupations or sports (e.g., diving). The recent development, again in Australia, of a test that uses dry powder mannitol has promise for use in the laboratory, the office, or for testing in the field. AHR to mannitol identifies people with EIA and is an estimate of its severity. The mannitol response is modified by drugs used to prevent EIA, implying that similar mediators are involved. A mannitol test can be used to monitor response to steroids and is more sensitive than histamine for identifying persistent airway hyperresponsiveness in asthmatics well controlled on steroids. These findings suggest that indirect challenges give more useful clinical information about currently active asthma and the response to treatment than direct challenge and they will become more widely used.

The importance of serum IgE for level and longitudinal change in airways hyperresponsiveness in COPD

BACKGROUND

Airways hyperresponsiveness (AHR) is an important feature of patients with chronic obstructive pulmonary disease (COPD). Little is known about factors that modulate AHR in COPD.

OBJECTIVE

To study these factors, we performed a long-term, double-blind, parallel intervention study in 58 male, non-allergic patients with COPD.

METHODS

During a period of 2 years, patients were treated with inhaled budesonide (1600 microg/day), inhaled budesonide (1600 microg/day) plus oral prednisolone (5 mg/day), or placebo. PC20 histamine was measured at 4-monthly intervals. The influence of treatment, smoking, age, level of lung function, initial serum IgE level and peripheral blood eosinophils on level and longitudinal change of PC20 histamine was analysed.

RESULTS

During follow-up, PC20 decreased in our group, and this decrease was not influenced by treatment. PC20 tended to decrease faster in current smokers than in ex-smokers. PC20 was significantly associated with pre-challenge FEV1 at each time point. Level nor decline of PC20 were significantly related to age. A higher initial serum IgE level was independently associated with a lower PC20. Moreover, a higher initial serum IgE level was associated with a slower annual decline of PC20, regardless of treatment, pre-challenge FEV1, and other modulating factors. No significant associations were found between initial blood eosinophils and level or decline of PC20.

CONCLUSION

We conclude that AHR increases over time in non-allergic patients with COPD. Treatment with an inhaled corticosteroid alone or in combination with oral prednisolone does not change this increase. Our study suggests an important role for IgE in the course of the disease, since a higher initial serum IgE level predicts a more favourable course with regard to annual decline of PC20 histamine.

Asthma, airways responsiveness and air pollution in two contrasting districts of northern England

BACKGROUND

To assess the possible magnitude of differences between normal populations an epidemiological investigation of asthma was conducted in two strongly contrasting districts of northern England--rural West Cumbria on the west coast and urban Newcastle upon Tyne on the east coast.

METHODS

A cross sectional survey of randomly identified men aged 20-44 years was conducted in two phases: phase 1, a postal survey of respiratory symptoms and asthma medication in 3000 men from each district; and phase 2, a clinical assessment of 300 men from each district comprising investigator administered questionnaires, skin prick tests, spirometry, and methacholine challenge tests.

RESULTS

The phase 1 (but not phase 2) study showed a small excess of "ever wheezed" in Newcastle (44% versus 40%), but neither phase showed differences between the two districts for recent wheeze or for other symptoms characteristic of asthma. There were also no differences with regard to diagnosed asthma, current asthma medication, spirometric parameters, or airways responsiveness. The prevalence of quantifiable airways responsiveness (PD20 < or = 6400 micrograms) was 27.7% in West Cumbria and 28.2% in Newcastle. Regression analyses showed that PD20 was negatively associated with atopy and positively with forced expiratory volume in one second (FEV1); that an association between PD20 and current smoking could be explained by diminished FEV1; and that PD20 was not related to geographical site of residence.

CONCLUSIONS

Neither airways responsiveness nor the other parameters of diagnostic relevance to asthma varied much between the two study populations, despite the apparent environmental differences. The most obvious of these were the levels of outdoor air pollution attributable to vehicle exhaust emissions, the ambient levels of which were 2-10 fold greater in Newcastle. Our findings consequently shed some doubt over the role of such pollution in perceived recent increases in asthma prevalence. It is possible, however, that an air pollution effect in Newcastle has been balanced by asthmagenic effects of other agents in West Cumbria.

Factors affecting peak expiratory flow variability and bronchial reactivity in a random population sample

BACKGROUND

Bronchial reactivity measurements are widely used in epidemiological studies to provide an objective marker of asthma. There are, however, several potential advantages of measuring peak expiratory flow (PEF) variability instead, particularly in large studies. PEF variability and bronchial reactivity were compared in a population sample to assess the relationships of the two measurements to factors known to be associated with airways disease, and to compare their response rates.

METHODS

Subjects aged 18-65 were randomly selected from the electoral register of an administrative area in eastern England and randomised to attend either for a bronchial challenge test measuring the provocative dose of methacholine producing a 20% fall in FEV1 (PD20), or to measure PEF at two hourly intervals during waking hours for one week. Skin tests with common allergens were performed and a smoking history obtained. PEF variability was expressed as the amplitude % mean (highest - lowest x 100/mean).

RESULTS

A total of 273 subjects (69%) collected a PEF meter but a completed record sheet was returned by only 247 (62%); this was still significantly more than the 202 subjects (54%) who attended for and successfully completed a challenge test. Amplitude % mean was higher in women than in men (9.7% v 8.5%). In multiple regression analysis amplitude % mean increased significantly with age, mean skin weal diameter, and with current smoking. The odds of having a PD20 below 24.5 mumol increased with mean skin weal diameter and were greater in current smokers. Neither age nor sex had a significant effect on bronchial reactivity but there were significant interactions between age and the effects of both smoking and atopy.

CONCLUSIONS

The higher response rate associated with the use of PEF variability measurement, and the association with factors implicated in the pathogenesis of airways disease, suggest that PEF variability would be a useful measurement to employ in epidemiological studies.

Functional alterations accompanying a rapid decline in ventilatory function

In a study of two groups of healthy males matched for age, smoking habits, and duration of follow-up, but differing in the rapidity of decline of FEV1 and/or vital capacity (VC), we measured lung volumes before and after bronchodilator inhalation, forced expiratory flows, diffusion capacity for CO (DLCO), and total respiratory impedance. A discriminant analysis showed that the separation between the two groups was achieved best by DLCO, weight, and FEV1/VC among the smokers and by body height and DLCO among the nonsmokers. The fact that DLCO turns out to discriminate between people with a rapid and a normal spirographic decline in the present group points to the possibility of using this measurement, in combination with FEV1/VC and weight, as a predictor of rapid decline of lung function in middle-aged healthy male smokers.

The lung health study: airway responsiveness to inhaled methacholine in smokers with mild to moderate airflow limitation. The Lung Health Study Research Group

As part of a multicenter clinical trial (Lung Health Study), methacholine inhalation challenge testing was performed in 5,877 current cigarette smokers, ages 35 to 59 yr (mean 48.5 +/- 6.8 yr), with borderline to moderate airflow limitation (FEV1/FVC ratio 63.0 +/- 5.5). The test was successfully completed in 96.4% of subjects, of whom 63% were male and 95.9% were white. Symptomatic reactions to methacholine were rarely severe enough to require evaluation by a trial physician. Nonspecific airways hyperresponsiveness (AHR) was defined as a greater than or equal to 20% decline in FEV1 from the post-diluent control value after inhalation of less than or equal to 25 mg/ml methacholine. AHR was noted in a significantly higher percentage of women (85.1%) than men (58.9%). Moreover, nearly twice as many women as men (46.6 and 23.9%, respectively) responded to less than or equal to 5 mg/ml of methacholine. In both men and women, baseline degree of airways obstruction and clinical center were strongly associated with AHR (p less than 0.001), whereas age was not. Additional associations with AHR were analyzed in men and women separately using logistic regression after adjustment for baseline lung function, age, and center-to-center differences. In men, AHR was significantly related to symptoms of wheeze, chronic cough and/or sputum, and a history of asthma or hay fever (p less than 0.004), but not to current or lifetime tobacco use. By contrast, among women, AHR was not significantly associated with chronic cough and/or phlegm (p greater than 0.05) or a past history of asthma or hay fever (p greater than 0.1) and was only weakly related to wheeze and current asthma (p = 0.04), as well as to cigarette pack-years (p = 0.044). These results indicate that most continuing smokers with functional evidence of early chronic obstructive pulmonary disease have nonspecific AHR that is strongly related to gender and baseline lung function and, to a lesser extent, to respiratory symptoms. The reason for the striking effect of gender on AHR in early chronic obstructive pulmonary disease is unclear but cannot be attributed to male-female differences in age, cigarette use, presence of asthma, or baseline degree of airflow obstruction.

Effects of inhaled budesonide on spirometric values, reversibility, airway responsiveness, and cough threshold in smokers with chronic obstructive lung disease

Inhaled corticosteroids are known to reduce respiratory symptoms and airway responsiveness in allergic patients with asthma. The aim of the present randomised, double blind study was to assess the effect of eight weeks' treatment with inhaled budesonide in non-allergic smokers with chronic obstructive lung disease. Twenty four subjects (23 male) entered the study. Their ages ranged from 40 to 70 (mean 57) years, with a mean of 35 (range 9-80) pack years of smoking; the mean FEV1 was 53% (range 32-74%) predicted and geometric mean PC20 (histamine concentration causing a 20% fall in FEV1) 0.96 (range 0.07-7.82) mg/ml. After a two week washout, single blind, placebo period, 12 patients were allocated to treatment with budesonide 1600 microgram/day and 12 to placebo for eight weeks. The only additional drug to be taken was ipratropium bromide "if needed." Twenty one patients completed the study, 10 in the budesonide group and 11 in the placebo group. The standard deviation of the difference between duplicate measurements of PC20 histamine and citric acid cough threshold made two weeks apart was below one doubling dose step. There was a significant reduction in dyspnoea in the budesonide group, but otherwise no change in symptom scores or use of ipratropium bromide over the eight weeks of treatment within or between the two groups. No significant differences in spirometric values, peak expiratory flow, PC20 histamine, or citric acid cough threshold were found between the groups. Although differences were not significant, some of the changes showed a trend in favour of budesonide. Whether a longer observation period would show a significant influence of inhaled corticosteroids in patients with chronic obstructive lung disease remains to be determined.

Methacholine responsiveness among working populations. Relationship to smoking and airway caliber

It has been suggested that the development of bronchial hyperresponsiveness (BHR) in some smokers may be an intermediate event in the progression to chronic obstructive pulmonary disease in this group. If this is true, prevalence data on BHR in a general population should show an independent association between BHR and smoking status. To test this, we analyzed BHR to inhaled methacholine in 654 white men without known asthma, in relation to smoking, skin-test reactivity, type of work (office versus industrial), and indicators of baseline airway caliber (FEV1 % predicted and FEV1/FVC). BHR was measured in the traditional way (PC20) and as the slope of FEV1 versus the methacholine concentration (linear scale). A PC20 of less than 16 mg/ml was considered "responsive" for analyses of this outcome. We found that although a positive skin test, smoking, and being an industrial worker all appeared to be significant predictors of increased BHR (p less than 0.05), once FEV1 (% predicted) and FEV1/FVC% were taken into account, none of these variables alone remained significantly associated with BHR. The strongest predictors of BHR were prechallenge FEV1 and FEV1/FVC (both p less than 0.01). The combination of smoking, atopy, and work groups, which identified a small subgroup of atopic smokers who were office workers, also remained significantly associated with increased BHR. We also used a regression model that allowed for comparison of predictors for BHR between the most responsive subset of the population (n = 84) and the remainder of the study population.(ABSTRACT TRUNCATED AT 250 WORDS)

Differences in airway responsiveness in asthma and chronic airflow obstruction

In patients with chronic obstructive lung disease, it is difficult to distinguish clinically between asthma, chronic bronchitis, and emphysema. This is due in part to the fact that the original definitions were not mutually exclusive. Diagnosis has not been helped by the measurement of airway responsiveness to methacholine or histamine, since responsiveness seems to be increased as often in those with chronic airflow obstruction as in asthmatic patients.