Effects of smoking and changes in smoking habits on the decline of FEV1

The aim of this study was to examine the effects of cigarette smoking and changes in smoking habits on the decline of forced expiratory volume in the first second of expiration (FEV1). We studied 7,764 men and women for 5 yrs. The subjects were grouped according to self-reported smoking habits during the observation period. We found that persistent cigarette smoking, in particular heavy smoking, accelerated the decline in FEV1. In 310 subjects who quitted smoking during the observation period, the decline of FEV1 was less pronounced than the decline observed in persistent smokers. In subjects younger than 55 yrs of age, smoking reduction was associated with a less pronounced FEV1 decline, while in the elderly subjects smoking reduction had no effect on the FEV1 decline. An increase in the number of cigarettes smoked was generally associated with a more rapid decline of FEV1, while the beginning of smoking during the 5 yrs of observation did not seem to influence the decline of FEV1. We conclude that smoking cessation or reduction may lead to a demonstrable beneficial effect on the FEV1 decline within a few years.     

Smoking cessation--but not smoking reduction--improves the annual decline in FEV1 in occupationally exposed workers

INTRODUCTION: Individuals exposed both to cigarette smoke and respiratory pollutants at work incur a greater risk of development of airway hyperresponsiveness (AHR) and accelerated decline in forced expiratory volume in 1 s (FEV1) than that incurred by subjects undergoing each exposure separately. We examined whether smoking cessation or smoking reduction improves AHR and thereby slows down the decline in FEV1 in occupationally exposed workers. METHODS: We examined 165 workers (137 males and 28 females) participating in a smoking cessation programme. Nicotine tablets were used for smoking cessation or smoking reduction. Respiratory symptoms were assessed by questionnaire, FEV1 by spirometry and AHR by methacholine challenge test. At 1 year, subjects were classified into quitters, reducers, or continuing smokers. RESULTS: Sixty-seven subjects completed the study (32 quitters; 17 reducers; 18 continuing smokers). Respiratory symptoms improved markedly in quitters (P<0.001 for all comparisons) and less so in reducers (P values between 0.163 and 0.027). At 1 year, FEV1 had slightly but significantly improved in quitters (P=0.006 vs. smokers; P=0.038 vs. reducers) and markedly deteriorated in reducers and continuing smokers. Concurrent, 1-year change in AHR did not differ significantly among the groups. CONCLUSION: In occupationally exposed workers, stopping smoking markedly improved respiratory symptoms and, in males, slowed the annual decline in FEV1. Smoking reduction resulted in smaller improvements in symptoms but deterioration in FEV1. These findings were independent of AHR. While smoking cessation should remain the ultimate goal in workplace cessation programmes more studies are necessary to better ascertain the benefits of smoking reduction.     

The environment and risk factors for atopy

Atopy is the genetic potential to manifest the trinity of classic allergic diseases—atopic dermatitis, allergic rhinitis, and asthma. All have been observed to have increased over the past several decades. The interplay of the genetics of atopy with various environmental exposures may manifest itself in the form of allergic phenotypes or paradoxically may actually suppress the allergic response. The hygiene hypothesis offers an explanation of why certain environmental exposures early in life may suppress or activate clinical disease. Primary prevention is directed at preventing the clinical manifestations of atopy by suppressing or delaying the onset of allergic sensitivity. Studies of primary prevention have brought mixed results. Secondary prevention is directed at reducing or removing triggers in the environment of the sensitized individual. Secondary prevention measures directed at one allergen have not proven successful. Comprehensive intervention programs dealing with both allergens and other potential triggers appear beneficial.     

Working in swine-confinement buildings causes an accelerated decline in FEV1: a 7-yr follow-up of Danish farmers.

Work in swine confinement units causes exposure to high levels of organic dust and is associated with a high prevalence of work-related respiratory symptoms and probably with accelerated decline in forced expiratory volume in one second (FEV1). A 7-yr follow-up on FEV1, forced vital capacity (FVC), bronchial reactivity, and respiratory symptoms was performed on 181 Danish farmers. The participation rate was 76.3% and nonparticipants had more symptoms, were more likely to be current-smokers and had lower lung function in the first survey than participants in both surveys. Farmers who worked exclusively with pigs in the follow-up had an accelerated decline in FEV1 but not in FVC compared with dairy farmers, where the observed decline in FEV1 was close to the expected. For a nonsmoking pig farmer compared to a nonsmoking dairy farmer the mean additional decline in FEV1 was 17 mL x yr(-1) (53.0 mL x yr(-1) versus 36.1 mL x yr(-1)). The authors conclude that working in swine confinement units causes an accelerated decline in forced expiratory volume in one second but not in forced vital capacity. The mean decline is approximately 0.5 L during a working life and some farmers will develop clinically significant airway obstruction due to work in swine confinement units.     

Chronic respiratory symptoms, von Willebrand factor and longitudinal decline in FEV1

Although some risk factors for accelerated decline in forced expiratory volume in 1 s (FEV1) such as cigarette smoking, are well defined, it is not possible to identify those individuals with the most rapid rates of decline. Von Willebrand factor (vWF) is a product of both the pulmonary and systemic endothelium, and serum levels are raised during episodes of acute bronchitis. We hypothesized that raised serum levels of vWF may indicate sub-clinical pulmonary injury and so may predict subsequent accelerated decline in FEV1. The aims of this study were 1. to define the prevalence of chronic respiratory symptoms and obstructive airway disease in an inner-city British population and 2. to determine whether elevated levels of von Willebrand factor (vWF) identify those individuals at risk for more rapid decline in FEV1 over time. In 1987, all 2013 individuals aged 45 to 74 years at an inner-city general practice were mailed a respiratory symptom questionnaire. One in six of the responders were asked to attend for spirometry and for assessment of serum vWF. In 1996, those individuals who had spirometry and vWF assessed in 1987 were traced, and repeat spirometry was performed. In 1987, 1527 of 2013 (75.8%) individuals completed the questionnaire. Forty-two point two percent of responders reported shortness of breath on hills, 34.7% reported wheeze and 31.6% reported mucus hypersecretion. Smokers were more likely to report these symptoms. Two hundred and ten of the 251 (84%) individuals approached had spirometry and vWF assessed. Eleven percent of these had both an FEV1 < 75% predicted and a forced expiratory ratio (FEV1 forced vital capacity (FVC)) < 70%. Sub-normal spirometry was associated with wheeze, mucus hypersecretion, cigarette smoking and increasing age. By 1996, 32 (15%) of the original group of 210 individuals had died, and 117 of the remaining 178 (66%) had spirometry repeated. FEV1 < 75% predicted was a strong predictor of interim mortality, independent of age, sex and smoking history. The average decline in FEV1 was 46.7 ml yr-1. There was no significant correlation between serum vWF levels and subsequent decline in FEV1. Chronic respiratory symptoms and spirometric evidence of airflow limitation are common in inner-city residents of the U.K., and are associated with smoking history. Much of this disease is unrecognised by health professionals. An FEV1 < 75% predicted is a strong independent predictor of subsequent mortality. The measurement of serum vWF levels is unhelpful in identifying those individuals at increased risk of accelerated decline in FEV1.     

Risk factors of soybean epidemic asthma. The role of smoking and atopy.

Epidemics of emergency room admissions for asthma occurring in Barcelona during the period 1981 to 1987 were caused by inhalation of soybean dust. To investigate the risk factors that determined why some asthma patients became reactive to soybean and were consequently affected by the asthma epidemics of Barcelona but others did not do so, a case-control study was conducted during 1989, 2 yr after the cessation of asthma epidemics. Patients with asthma admitted in emergency room services during epidemic asthma days (n = 169) were compared with asthma patients admitted in the same services during nonepidemic days and who were never admitted during the epidemics (n = 147). Risk factors other than soybean exposure, namely skin reactivity against at least one common allergen (odds ratio [OR] 3.0, 1.7 to 5.3), age over 64 yr (OR 2.8, 1.4 to 6.0), cigarette smoking at the time of the epidemics (OR 2.3, 1.2 to 2.4), past smoking (OR 1.8, 0.9 to 3.7), and total immunoglobulin E (IgE) higher than 100 IU/ml (OR 1.7, 1.0 to 3.0), were found independently related to epidemic asthma. The role of smoking was especially important for those who had a positive skin reaction and were exposed to soybean dust (OR 7.9, 1.8 to 36.0). In this group, a dose-response pattern with pack-years was observed (p less than 0.01). The present findings suggest a multifactorial process for epidemic asthma, in which atopy and cigarette smoking played an important synergistic role. This has a preventive potential for IgE-related asthma.     

Methacholine responsiveness, respiratory symptoms and pulmonary function in aluminum potroom workers

The relationship between nonspecific bronchial reactivity and work-related asthmatic symptoms was examined in a cross-sectional study of 337 aluminium potroom workers by a shortened method of continuous methacholine nebulization. The provocative concentration producing a 20% fall in forced expiratory volume in one second (FEV1) (PC20) was less than or equal to 8 mg.ml-1 (hyperresponsiveness) in 17 workers (5%), whilst minor responsiveness (8 mg.ml-1 less than PC20 less than 32 mg.ml-1) was present in 24 subjects (7%). The prevalence of work-related asthmatic symptoms was 9%. Female sex, ex-smoker and airflow limitation were significant predictors of methacholine responsiveness (p less than 0.05). In a multiple logistic regression analysis the odds ratios (OR) for work-related asthmatic symptoms was 10.8 (95% confidence interval: 2.9-40.6) for hyperresponsiveness and 4.4 (95% confidence interval: 1.2-16.4) for minor responsiveness. The sensitivity, specificity and predictivity of PC20 less than 32 mg.ml-1 for work-related asthmatic symptoms were 35, 92 and 35%, respectively, whilst the agreement, when adjusted for the by chance expectation, was 0.27 (95% confidence interval: 0.10-0.54). Although a significant association was found between bronchial reactivity and work-related asthmatic symptoms, the usefulness of the methacholine test as a tool for detection of work-related asthmatic symptoms appears to be of limited value due to its low sensitivity.     

FEV1/FEV6 and FEV6 as an alternative for FEV1/FVC and FVC in the spirometric detection of airway obstruction and restriction

STUDY OBJECTIVES: To evaluate the use of the FEV(1)/forced expiratory volume at 6 s of exhalation (FEV(6)) ratio and FEV(6) as an alternative for FEV(1)/FVC and FVC in the detection of airway obstruction and lung restriction, respectively. SETTING: Pulmonary function laboratory of the Academic Hospital of the Free University of Brussels. PARTICIPANTS: A total of 11,676 spirometric examinations were analyzed on subjects with the following characteristics: white race; 20 to 80 years of age; 7,010 men and 4,666 women; and able to exhale for at least 6 s. METHODS: Published reference equations were used to determine lower limits of normal (LLN) for FEV(6), FVC, FEV(1)/FEV(6), and FEV(1)/FVC. We considered a subject to have obstruction if FEV(1)/FVC was below its LLN. A restrictive spirometric pattern was defined as FVC below its LLN, in the absence of obstruction. From these data, sensitivity and specificity of FEV(1)/FEV(6) and FEV(6) were calculated. RESULTS: For the spirometric diagnosis of airway obstruction, FEV(1)/FEV(6) sensitivity was 94.0% and specificity was 93.1%; the positive predictive value (PPV) and negative predictive value (NPV) were 89.8% and 96.0%, respectively. The prevalence of obstruction in the entire study population was 39.5%. For the spirometric detection of a restrictive pattern, FEV(6) sensitivity was 83.2% and specificity was 99.6%; the PPVs and NPVs were 97.4% and 96.9%, respectively. The prevalence of a restrictive pattern was 15.7%. Similar results were obtained for male and female subjects. When diagnostic interpretation differed between the two indexes, measured values were close to the LLN. CONCLUSIONS: The FEV(1)/FEV(6) ratio can be used as a valid alternative for FEV(1)/FVC in the diagnosis of airway obstruction, especially for screening purposes in high-risk populations for COPD in primary care. In addition, FEV(6) is an acceptable surrogate for FVC in the detection of a spirometric restrictive pattern. Using FEV(6) instead of FVC has the advantage that the end of a spirometric examination is more explicitly defined and is easier to achieve.     

A longitudinal study of baseline FEV1 and bronchial responsiveness in patients with asthma.

The effect of initial airway calibre on the response to bronchial provocation is unclear. Theoretically, geometric relationships within the airways might influence the measurement of responsiveness, particularly since a given change in calibre will produce a disproportionately greater reduction in flow in airways which are already narrowed. We have examined the relationship between serial measurements of prechallenge forced expiratory volume in one second (FEV1) and responsiveness to methacholine (PD20) in 8 children and 12 adults with asthma. Measurements were made every 2-3 wks for 12-18 months and all patients kept a daily record of symptoms and twice daily measurements of peak expiratory flow (PEF). Spearman's rank correlation coefficient (rho) for the relationship PD20 versus pre-challenge FEV1 was derived for each patient and varied widely within the group (range -0.22 to 0.73, mean 0.31); the strength of this correlation was not related to a patient's mean FEV1 % predicted, but was related to the degree to which PD20 and pre-challenge FEV1 themselves reflected concurrent asthma severity (mean morning PEF and mean symptom scores for the three days around each test). This suggests that the observed relationship between pre-challenge FEV1 and PD20 may be due less to the influence of airway geometric factors, which might be expected to be present in all patients, but rather that pre-challenge FEV1 is reflecting the severity of the underlying disease. Larger studies will be needed to test this hypothesis further.     

Lung function, asthma paradox, atopy, and risk factors in Mexican spirometry-diagnosed asthmatic patients.

Despite long-term studies, still not much is known about the asthma triggering factors and its sometimes controversial results. Probably one of the major problems of controversy is the lack of specific and accurate diagnosis of this disease. The aim of this study was to assess lung function, atopy, and environmental factors in spirometry-diagnosed asthmatic patients. Time series of daily counts of hospital emergency admissions were constructed for known asthmatic subjects. Spirometry, chest radiograph, arterial gasometry, skin tests, environmental SO2 levels, and climatic parameters were evaluated. Family asthma history was observed in a high proportion of asthmatic patients and it correlated marginally with severity of asthma. A seasonal trend in asthma frequency was recorded and it was more common in the urban area and in those living in the margins of the city. The most frequent asthma type recorded was the severe persistent asthma. More than 50% of subjects had subresponse to bronchodilator; asthma paradox was recorded in 10.8%. Positive skin tests were observed in 36.9% and SO2 levels did not correlate with asthma attacks. Paradox asthma or tolerance may be developed by asthmatic subjects during chronic treatment with short-acting 92-agonists. To avoid side effects and to decrease the morbidity and mortality associated with the usage of antiasthma medications, it is essential to identify quickly those subjects that respond abnormally to the short-acting P2-agonist.     

Spirometry, rapid FEV1 decline, and lung cancer among asbestos exposed heavy smokers

We assessed whether spirometric measurements are associated with the development of accelerated FEV(1) decline and lung cancer among active and previous smokers with a wide range of lung function. Bivariate and multivariate analyses that adjusted for age, intervention arm, smoking status at enrollment and smoking history, years exposed to asbestos, and evidence of asbestosis were used to assess whether baseline FEV(1) and FEV(1)/FVC ratio were associated with accelerated FEV(1) decline and incident lung cancer. The 3,041 participants enrolled from 1985 to 1994 were followed through April 30, 2005. Baseline FEV(1)/FVC ratio<0.7 was significantly associated with an increased risk for rapid lung function decline (OR=1.73; 95% CI 1.31-2.28; p<0.001). Baseline FEV(1)/FVC ratio<0.7 was also significantly associated with an increased risk of developing lung cancer, even when baseline FEV(1) was >80%. Lung cancer risk among participants with baseline airflow obstruction and FEV(1)<60% was 4-fold higher than participants without baseline airflow obstruction and FEV(1)>80% (p<0.001), even among former smokers. These data indicate an FEV(1)/FVC<0.7 among smokers is significantly associated with faster airflow loss, and an increased risk for developing lung cancer, even among those individuals with a normal FEV(1).     

Rapid decline in FEV1 in grain handlers. Relation to level of dust exposure

We have prospectively studied the respiratory health of a cohort of grain elevator workers in the Canadian west coast terminal elevators, beginning in 1975 and following them for 6 yr. We have used a "nested" case-control model to identify determinants of the worst trend in FEV1 over this period. The 10% of participants in this category had a mean decline of greater than 100 ml/yr. They were significantly more likely to have had a decline in FEV1 over a work week and to have nonspecific bronchial hyperreactivity. There was a significant relationship between the odds ratio of being a case and the mean level of dust exposure associated with the job and location at the work site; cases were associated with mean total dust levels greater than 5 mg/m3. We found no relationship between the odds ratio of being a case and a number of host factors, such as immediate skin reactivity to common allergens, history of asthma, bronchitis, or hay fever, or presence of respiratory symptoms. We conclude that exposure to grain dust at levels greater than 5 mg/m3 is associated with a serious adverse trend in FEV1.     

Obstructive and restrictive spirometric patterns: fixed cut-offs for FEV1/FEV6 and FEV6.

The purpose of this study was to determine fixed cut-off points for forced expiratory volume in one second (FEV(1))/FEV(6) and FEV(6) as an alternative for FEV(1)/forced vital capacity (FVC) and FVC in the detection of obstructive and restrictive spirometric patterns, respectively. For the study, a total of 11,676 spirometric examinations, which took place on Caucasian subjects aged between 20-80 yrs, were analysed. Receiver-operator characteristic curves were used to determine the FEV(1)/FEV(6) ratio and FEV(6) value that corresponded to the optimal combination of sensitivity and specificity, compared with the commonly used fixed cut-off term for FEV(1)/FVC and FVC. The data from the current study indicate that FEV(1)/ FEV(6) <73% and FEV(6) <82% predicted can be used as a valid alternative for the FEV(1)/FVC <70% and FVC <80% pred cut-off points for the detection of obstruction and restriction, respectively. The statistical analysis demonstrated very good, overall, agreement between the two categorisation schemes. For the spirometric diagnosis of airway obstruction (prevalence of 45.9%), FEV(1)/FEV(6) sensitivity and specificity were 94.4 and 93.3%, respectively; the positive and negative predictive values were 92.2 and 95.2%, respectively. For the spirometric detection of a restrictive pattern (prevalence of 14.9%), FEV(6) sensitivity and specificity were 95.9 and 98.6%, respectively; the positive and negative predictive values were 92.2 and 99.3%, respectively. This study demonstrates that forced expiratory volume in one second/forced expiratory volume in six seconds <73% and forced expiratory volume in six seconds <82% predicted, can be used as valid alternatives to forced expiratory volume in one second/forced vital capacity <70% and forced vital capacity <80% predicted, as fixed cut-off terms for the detection of an obstructive or restrictive spirometric pattern in adults.