Relationship of constitutional factors and cigarette smoking to decrease in 1-second forced expiratory volume

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.

Relationship between bronchial reversibility and tracheobronchial clearance in patients with chronic bronchitis

BACKGROUND

Patients with chronic bronchitis show a large intersubject variation in sputum rheology, tracheobronchial clearance, and reversibility of airflow obstruction to beta 2 agonists. The bronchial mediators which are known to cause bronchoconstriction, mucosal oedema, mucus hypersecretion, and cough can also affect mucociliary transport. The aim of this study was to ascertain whether changes in tracheobronchial clearance and sputum rheological properties in patients with chronic bronchitis were associated with a specific degree of airflow reversibility assessed as the bronchial response to an inhaled beta 2 agonist (fenoterol 400 micrograms).

METHODS

Bronchial reversibility (percentage change in baseline forced expiratory volume in one second (FEV1)) was measured in 26 patients with chronic bronchitis on three separate occasions, at least one week apart. Tracheobronchial clearance was evaluated by a non-invasive radioaerosol technique, and an oscillatory viscometer was used for measuring sputum apparent viscosity and elasticity. The number of coughs (productive and nonproductive coughs), the wet weight of sputum, and its radioaerosol content were recorded during the six hour clearance period, as well as the 24 hour sputum production.

RESULTS

The change in FEV1 after fenoterol was less than 15% in 12 patients and more than 15% in 14. Patients with airways reversibility of more than 15% had faster tracheobronchial clearance, more coughs, lower sputum viscosity and elasticity, and larger 24 hour sputum production than those with airways reversibility of less than 15%.

CONCLUSIONS

In patients with chronic bronchitis a large bronchodilator response is associated with faster clearance of mucus by mucociliary transport and coughing.

Airway responsiveness and job selection: a study in coal miners and non-mining controls

BACKGROUND

It has been suggested that health related job selection is a major cause of the healthy worker effect, and may result in inaccurate estimates of health risks of exposures in the working environment. Improved understanding of self selection, including the role of airway hyperresponsiveness, should improve accuracy in estimating occupational risks.

METHODS

We evaluated symptoms of the respiratory tract, lung function, occupational and smoking histories, and airway responsiveness from a cross sectional survey of 478 underground bituminous coal miners and non-mining controls. Workers with abnormal spirometry were excluded from methacholine testing.

RESULTS

Methacholine responsiveness (> or = 15% decline in forced expiratory volume in one second) was associated in both miners and controls with reduced ventilatory lung function and an increased risk of respiratory symptoms. Miners with the longest duration of work at the coal face had a low prevalence of methacholine responsiveness, compared with miners who had never worked at the coal face (12% v 39%, P < 0.01). Throughout their mining careers, miners who responded to methacholine were consistently less likely to have worked in dusty jobs than miners who did not respond to methacholine.

CONCLUSIONS

These results provide evidence that workers who are employed in dusty jobs are less likely than their unexposed coworkers to show increased non-specific airway responsiveness, presumably as a result of health related job selection. Surveys of workers in which responsiveness data are unavailable may underestimate the effects of dust exposure on respiratory health.

Asymptomatic bronchial hyperreactivity and the development of asthma and other respiratory tract illnesses in children

BACKGROUND

It is not clear whether asymptomatic bronchial hyperresponsiveness (BHR) in children is a risk factor for the subsequent development of asthma. A longitudinal study was conducted to determine the predictive value of BHR for the development of asthma in a primary care patient population.

METHODS

A standard free running asthma screening test (FRAST) was applied to 956 schoolchildren aged between 4 and 11 years in 1985. Peak expiratory flow (PEF) rates were measured before hard running for six minutes and following a three minute rest period. Children with a fall in PEF of more than 15% were labelled as having a positive FRAST. Clinical data from the patients' notes and from symptom questionnaires were compared with age and sex matched controls for children known to have asthma, and for those with a positive FRAST but no asthma (BHR group). Over the ensuing six years to 1991 further clinical data were gathered to compare the development of asthma and other diseases of the airways in both the BHR groups and their controls.

RESULTS

Of the 956 children exercised in 1985, 60 who were not known to have asthma had an abnormal test. Of the 55 of these studied in 1991, 32 (58%) had developed asthma. The sensitivity of a positive FRAST for the development of asthma was 58%, its specificity 97%, and positive predictive value 72%. Hay fever, eczema, otitis media, "bronchitis," and family history of atopy also occurred more commonly in this group.

CONCLUSIONS

Asymptomatic BHR, as shown by exercise challenge, can predict the development of clinical asthma. This study has also shown a relation between BHR, asthma, and other diseases of the airways, notably upper respiratory tract infection, "bronchitis," and otitis media.

A 10 year follow up of 180 adults with bronchial asthma: factors important for the decline in lung function

BACKGROUND

Little is known about the factors that determine outcome in asthma. The purpose of this study was to describe the relation of various factors of potential importance to the rate of decline in lung function in adults with intrinsic and extrinsic asthma.

METHODS

Of 180 asthmatic patients, 143 (79%) participated in a 10 year follow up examination. At the time of enrollment all patients underwent certain tests for asthma (case history, total IgE, skinprick tests, the radioallergosorbent test (RAST), histamine release from basophil leucocytes, and specific bronchial provocations). On the basis of these tests 94 patients had intrinsic asthma and 49 extrinsic asthma.

RESULTS

Patients with intrinsic asthma had an annual decline in FEV1 of 50 ml, whereas those with extrinsic asthma had a decline of 22.5 ml; the rate of decline of lung function increased with increasing age in both groups. An inverse relation between initial FEV1 and decline in FEV1 (the "horse racing effect") was found for the patients with extrinsic asthma but not for the patients with intrinsic asthma. There was no relation between rate of decline in lung function and number of cigarettes smoked. A high degree of airway variability--that is, reversibility in FEV1--at the time of enrollment was found to be associated with a steeper decline in lung function in patients with intrinsic asthma, whereas increasing degrees of obstruction (decreasing FEV1/VC ratio at enrollment) and need for treatment with corticosteroids were associated with a more pronounced decline in FEV1 in patients with extrinsic asthma.

CONCLUSIONS

The rate of decline in lung function is greater in patients with intrinsic asthma than in patients with extrinsic asthma; the prognosis for intrinsic and extrinsic asthma is to some extent influenced by different factors, which suggests that the pathogenetic mechanisms underlying intrinsic and extrinsic asthma may differ.

Decline of lung function and development of chronic airflow limitation: a longitudinal study of non-smokers and smokers in Busselton, Western Australia

Data collected during seven population health surveys over 18 years in Busselton, Western Australia, were examined to determine the effect of smoking on lung function and to investigate the development of chronic airflow limitation. Lung function was measured and details of respiratory illness and smoking histories were collected from subjects attending surveys at three year intervals from 1966 to 1984. Data from ex-smokers and asthmatic patients (diagnosis based on answer to questionnaire) were excluded. Regression of height adjusted forced expiratory volume in one second (FEV1) on age was calculated individually for 759 non-smokers and 225 regular smokers with four or more observations. Decline in height adjusted FEV1 was similar for men and women. In smokers the rate of decline in FEV1 was greater than in non-smokers and was related to the amount smoked, to the extent that a smoker could expect a 20-30% greater rate of decline than a non-smoker of the same age. Chronic airflow limitation (defined as FEV1/FEV less than 65% or FEV1 less than 65% predicted on at least two occasions) was common, occurring in 24% of men and 18% of women who were regular smokers and in 5% of male and 8% of female non-smokers. These figures are higher than those reported in other populations, especially for women and for non-smokers. Not all chronic airflow limitation was associated with respiratory symptoms, confirming that the condition may be unrecognised until it is advanced.

Respiratory symptoms as predictors of 27 year mortality in a representative sample of British adults

OBJECTIVE

To examine associations between reported respiratory symptoms (as elicited by questionnaire) and subsequent mortality.

DESIGN

Prospective cohort study.

SETTING

92 General practices in Great Britain.

PARTICIPANTS

A nationally representative sample of 1532 British men and women aged between 40 and 64.

MAIN OUTCOME MEASURES

Mortality from all causes, cardiovascular disease, lung cancer, and chronic bronchitis.

RESULTS

Subjects were interviewed in 1958 regarding various respiratory symptoms (including cough, phlegm, breathlessness, and wheeze) by using a questionnaire which formed the basis of the Medical Research Council's questionnaire on respiratory symptoms. By the end of 1985, 889 deaths had been reported, including 51 in men due to chronic bronchitis. After adjustment for differences in age and smoking habits death rates from chronic bronchitis in men who reported symptoms were greater than those in men who did not for each of the symptoms examined. The adjusted mortality ratios were 3.4 (95% confidence interval 1.8 to 6.5) for morning cough, 3.7 (2.0 to 6.9) for morning phlegm, 6.4 (3.0 to 13.8) for breathlessness when walking on the level, and 10.5 (4.4 to 24.6) for wheeze most days or nights. Mortality ratios were also significantly raised for four episodic symptoms not usually included in more recent respiratory symptom questionnaires--namely, occasional wheeze (mortality ratio 6.0; 95% confidence interval, 2.4 to 15.1), weather affects chest (5.7; 3.1 to 10.3), breathing different in summer (4.9; 2.8 to 8.6), and cold usually goes to chest (3.7; 2.0 to 6.8). The excess mortality associated with these symptoms remained significant after further adjustment for breathlessness or phlegm. Ratios for all cause mortality in men and women were also significantly raised for most respiratory symptoms, death rates being some 20-50% higher in people reporting symptoms after adjustment for age, sex, and smoking. Breathlessness was the only symptom significantly associated with excess mortality from cardiovascular disease (mortality ratio 1.4 (95% confidence interval 1.0 to 1.9) for breathlessness when walking on the level). Ratios were generally around unity and not significant for mortality due to lung cancer.

CONCLUSIONS

The results suggest that episodic symptoms, which often do not appear in standard respiratory questionnaires, predict subsequent mortality from chronic obstructive airways disease. This supports the hypothesis that reversible airflow obstruction may be a precursor of progressive and irreversible decline in ventilatory function.

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

Bronchial hyperresponsiveness to inhaled histamine in smokers is associated with an accelerated annual decline in FEV1 and low baseline FEV1 values. The evolution of bronchial hyperresponsiveness and whether it precedes or follows the accelerated decline in FEV1 and reduction in FEV1 is unknown. Measurements of the provocative concentration of inhaled histamine required to reduce FEV1 by 20% (PC20) were repeated after a four year interval in 27 male smokers (mean age 59 years, smoking on average 27 cigarettes a day in 1986) and 16 men who were ex-smokers in 1982 and who remained non-smokers until 1986 (mean age 53 years in 1986). These men were originally recruited to a prospective study in 1974 and had their first PC20 measurement in 1982. PC20 was positively related to baseline FEV1 in both smokers and ex-smokers in both 1982 and 1986 (r ranging from 0.56 to 0.76, p less than 0.01). In smokers mean FEV1 fell from 83% to 77% predicted (p less than 0.001) and geometric mean PC20 from 7.11 to 3.27 mg/ml (p less than 0.001) between 1982 and 1986. The change in PC20 in individual smokers over the four years was related to change in FEV1 (p = 0.012). In ex-smokers mean FEV1 was 93% predicted both in 1982 and in 1986 and there was no significant difference in geometric mean PC20 between 1982 (6.68 mg/ml) and 1986 (5.98 mg/ml). Thus in smokers there was an accelerated annual decline in FEV1 and an increase in bronchial hyperresponsiveness as FEV1 fell. The ex-smokers had comparable levels of bronchial hyperresponsiveness in 1982. Mean PC20 values were unchanged in 1986 in these men, who showed a normal age related decline in FEV1. These longitudinal results emphasise the importance of baseline airway geometry in influencing bronchial hyperresponsiveness to histamine in middle aged smokers and ex-smokers.

Pulmonary abnormalities in obligate heterozygotes for cystic fibrosis

Parents of children with cystic fibrosis have been reported to have a high prevalence of increased airway reactivity, but these studies were done in a select young, healthy, symptomless population. In the present study respiratory symptoms were examined in 315 unselected parents of children with cystic fibrosis and 162 parents of children with congenital heart disease (controls). The cardinal symptom of airway reactivity, wheezing, was somewhat more prevalent in cystic fibrosis parents than in controls, but for most subgroups this increased prevalence did not reach statistical significance. Among those who had never smoked, 38% of obligate heterozygotes for cystic fibrosis but only 25% of the controls reported wheezing (p less than 0.05). The cystic fibrosis parents who had never smoked but reported wheezing had lower FEV1 and FEF25-75, expressed as a percentage of the predicted value, than control parents; and an appreciable portion of the variance in pulmonary function was contributed by the interaction of heterozygosity for cystic fibrosis with wheezing. For cystic fibrosis parents, but not controls, the complaint of wheezing significantly contributed to the prediction of pulmonary function (FEV1 and FEF25-75). In addition, parents of children with cystic fibrosis reported having lung disease before the age of 16 more than twice as frequently as control parents. Other respiratory complaints, including dyspnoea, cough, bronchitis, and hay fever, were as common in controls as in cystic fibrosis heterozygotes. These data are consistent with the hypothesis that heterozygosity for cystic fibrosis is associated with increased airway reactivity and its symptoms, and that the cystic fibrosis heterozygotes who manifest airway reactivity and its symptoms may be at risk for poor pulmonary function.

Evaluation of physical health effects due to volcanic hazards: human studies

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Factors affecting the decline of ventilatory function in chronic bronchitis

Ninety six middle aged male patients with chronic bronchitis with relatively well preserved ventilatory function who were resident in Queensland, New South Wales, or Victoria took part in a prospective study to determine the relationship of various factors to the rate of decline of the FEV1. Thirty of the subjects withdrew, leaving 66 to be followed for four to six years. The mean rate of decline of the FEV1 was 58.6 (SD 51.4) ml/year. The subjects' ventilatory responses to bronchodilator and to methacholine (measures of bronchial lability) were significantly related to each other and to sputum eosinophilia. With a linear model for the data on 57 patients who had methacholine and skin tests the rate of decline of the FEV1 was found, after adjustment had been made for other variables, to be significantly related to State of residence, current smoking, response to bronchodilator, age, and occupational exposure to dust. Response to bronchodilator was interchangeable with response to methacholine. With the five variables in the model none of the following factors was related to the rate of decline of the FEV1:FEV1 on entry, FEV1% predicted normal, FEV1/VC%, skin test reaction, occupation on entry, history of sinusitis and rhinitis, and height. When data from all 66 subjects were introduced into the model, in addition to the five significant individual variables (FEV1/VC% X response to bronchodilator) was significantly related to the rate of decline of the FEV1. Of these prognostic indices, response to bronchodilator was independent of the initial FEV1, FEV/VC%, and FEV1% predicted. The difference between States, which was not explained by differences due to sampling or withdrawal of subjects, was due to a low rate of decline in Queensland.

Bronchial reactivity to inhaled histamine and annual rate of decline in FEV1 in male smokers and ex-smokers

We examined the relations between bronchial reactivity, baseline FEV1, and annual decline of height corrected FEV1 (delta FEV1/ht3) over 7.5 years in 227 men (117 smokers, 71 ex-smokers, and 39 non-smokers). Men with a clinical diagnosis of asthma or receiving bronchodilator treatment were excluded. Bronchial reactivity was determined as the provocation concentration (PC20) of inhaled histamine sufficient to reduce FEV1 by 20%; subjects were divided into reactors (PC20 less than or equal to 16 mg/ml) and non-reactors (PC20 greater than 16 mg/ml). Thirty per cent of smokers, 24% of ex-smokers, and 5% of non-smokers were reactors. When smokers who were reactors were compared with non-reactors, the reactors showed a lower baseline FEV1 as percentage predicted in 1981-2 (85% v 108%), and a faster delta FEV1/ht3 (14.1 v 9.2 ml/y/m3). Baseline FEV1 correlated with PC20 in both smokers (rs = 0.51) and ex-smokers (rs = 0.61), and all 15 subjects with an FEV1 under 80% of the predicted value were reactors. In ex-smokers delta FEV1/ht3 was similar in reactors and non-reactors (m 9.0 v 7.4 ml/y/m3), despite significant differences in baseline FEV1. When analysis was confined to men with a baseline FEV1 over 80% predicted, the prevalence of reactors was significantly increased among smokers and slightly increased among ex-smokers compared with non-smokers, though the mean FEV1 was higher in the non-smokers. Bronchial reactivity was not increased in smokers aged 35 years or less. In smokers delta FEV1/ht3 was faster in those with a personal history of allergy (usually allergic rhinitis), but was not related to a family history of allergic disease, total serum immunoglobulin E level, absolute blood eosinophil count, or skinprick test score. delta FEV1/ht3 was also faster in all subjects taking beta blocker drugs. Thus increased bronchial reactivity was associated with accelerated decline of FEV1 in smokers. Although the association could be a consequence of a lower lower baseline FEV1, a trend towards increased reactivity was found in smokers with normal baseline FEV1 and delta FEV1/ht3 was dissociated from increased reactivity in ex-smokers. These findings are compatible with the "Dutch hypothesis," but the association between allergic features and accelerated delta FEV1/ht3 was relatively weak, and increased reactivity may follow rather than precede the onset of smoking.

Bronchial responsiveness to methacholine in chronic bronchitis: relationship to airflow obstruction and cold air responsiveness

The response to inhaled methacholine is increased in patients with chronic airflow obstruction, but it is not known whether this is due to true hyperresponsiveness or is a result of the airflow obstruction. In asthmatics the response to methacholine correlates with the bronchoconstriction produced by hyperventilation of cold dry air. We studied 27 patients with a history of smoking and chronic bronchitis with a range of severity of airflow obstruction. Bronchial responses to methacholine (expressed as the provocation concentration causing a fall in FEV1 of 20%-PC20) and isocapnic hyperventilation of cold dry air were measured. In 19 patients the PC20 was less than 8 mg/ml (that is, in the asthmatic range) but only three developed bronchoconstriction in response to hyperventilation. There was a linear correlation between the log PC20 and the FEV1 (r = 0.86, p less than 0.001). The results suggest that in patients with chronic airflow obstruction the response to methacholine is determined by the degree of airflow obstruction, and cannot be used in the diagnosis of asthma in the absence of additional information.

Asthma from childhood at age 21: the patient and his disease

Information was obtained from 336 21-year-olds who had begun wheezing before the age of 7 about their knowledge of asthma and its effect on their current life style. Two-thirds of the subjects were still symptomatic. A control group of 62 subjects was available for comparison. Knowledge about asthma was poor, particularly among those with less troublesome symptoms. Half of those with frequent episodic asthma and one-third with persistent asthma did not regard excess use of bronchodilator aerosols as potentially dangerous. Over three-quarters of those with persistent asthma were not receiving adequate treatment. One-third of third of those with persistent asthma were missing substantial time from work because of respiratory illness, and a similar proportion were restricting sporting activities. The incidence of smoking was disturbingly high in all asthma groups. The higher the number of cigarettes ever smoked and the higher the current tobacco consumption the less satisfactory was the progress of asthma. Both cigarette smoking and severity of asthma contributed to chronic production of sputum. Children and teenagers with asthma should be educated to seek more appropriate medical help and thereby reduce morbidity.