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Urrutia Isabel, Capelastegui Alberto, Quintana José María, Muñiozguren Nerea, Basagana Xavier, Sunyer Jordi, and the Spanish Group of the European Community Respiratory Health Survey (ECRHS–I), Smoking habit, respiratory symptoms and lung function in young adults, European Journal of Public Health, Volume 15, Issue 2, April 2005, Pages 160–165, https://doi.org/10.1093/eurpub/cki113
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Abstract
Background: Smoking is the primary cause of deterioration in forced expiratory volume (FEV1) and the development of chronic obstructive lung disease. This study assessed the independent association of smoking with respiratory symptoms and lung function in young adults who took part in the European Community Respiratory Health Survey (ECRHS–I). Methods: Cross-sectional multi-centre survey of a general population of young adults aged 20(44 years in the ECRHS(I conducted in five Spanish centres. Several groups were created in an exclusive and descendent manner from the subjects who completed the questionnaire in accordance with how they had answered the questions: asthma-related symptoms; chronic bronchitis symptoms; minor respiratory symptoms; chronic cough; and no respiratory symptoms. Among a subset of the population, forced spirometry tests were performed. Linear and logistical regression models were used to assess the relationship of smoking in the presence of symptoms and its impact on lung function, adjusted by other important variables. Results: The prevalence of respiratory symptoms was higher among smokers. After adjusting for geographical area, total IgE, age, sex, and FEV1, smoking was associated with an increased risk of chronic bronchitis and other respiratory symptoms. These risks increased with increasing number of cigarettes smoked per day. A deterioration of FEV1 and the FEV1/FVC ratio was also directly associated with the number of cigarettes smoked per day. Conclusion: Even among young adults, smoking confers a high risk of developing a number of respiratory symptoms and the deterioration of the ventilatory function.
In adults, smoking is a primary cause of deteriorating forced expiratory volume in 1 second (FEV1) and strongly contributes to the progression towards chronic obstructive pulmonary disease (COPD).1 Most studies conducted to determine the impact of smoking on symptoms of asthma and other respiratory symptoms have been conducted among older individuals with a long history of smoking and did not assess the damage to lung function.2,3 In view of the considerable increase in smoking among younger adults,4,5 determining the impact of smoking on this sector of the population is of great public health importance.
Although the association between smoking, chronic bronchitis, and lung function impairment has been clearly demonstrated over the past 50 years, the association between smoking and asthma-related symptoms is less certain.6 Among adults aged 20–44 years, the European Community Respiratory Health Survey (ECRHS–I) observed an association between the number of cigarettes smoked per day and symptoms of coughing and chronic expectoration, as well as with lung function.7 Nevertheless, no studies have been conducted on the impact of smoking on lung function adjusted by presence of respiratory symptoms and other relevant variables.
The aim of this study was to assess the independent association of smoking with respiratory symptoms and lung function among young adults who took part in ECRHS(I survey conducted in five Spanish centres.
Material and Methods
Population
The methodology of the European Community Respiratory Health Survey (ECRHS–I) has been described previously.8,9 Briefly, it involved a cross-sectional, multi-centre study of the general population conducted in 48 geographical areas, predominantly in Western Europe. In Spain, the study was carried out in Albacete, Barcelona, Galdakao, Huelva, and Oviedo. During the first stage, potential participants were chosen by simple random sampling based on the municipal registers for each area, except in Oviedo where the electoral census was used. A sample of 1500 males and females aged 20–44 years was identified for each area. They were asked to complete a short questionnaire.10 Subsequently, a random sample of 20% of the initial sample from each area was invited to take part in a second, hospital-based stage of the study. This included a questionnaire on bronchial symptoms and smoking habit, measures of total and specific IgE, and tests for lung function. All tests were conducted only after obtaining informed consent of the patient.
Questionnaire
The measuring instrument was based on a questionnaire on bronchial symptoms developed by the International Union Against Tuberculosis and Lung Disease (IUATLD). It was modified by Burney et al. for the ECRHS survey.10,11 The Spanish version was devised by means of a back and forth translation method and validation of the original version in English.12
A series of groups were created in accordance with how subjects participating in the hospital-based phase who completed the main questionnaire answered the questions. These groups were formed in an ‘exclusive’ manner, such that each subject could only be placed in one group. Groups were also formed in a ‘descending’ manner so that a subject with asthma-related symptoms and a chronic cough was included only in the first of the groups. The groups were as follows:
Asthma-related symptoms group. This group included those who responded affirmatively to any of the following questions: Have you woken up during the night due to lack of air over the last 12 months? Have you had an asthma attack over the last 12 months? Are you currently taking any medication for asthma? A previous study has demonstrated that these questions accurately identify asthma patients. In a Spanish population, when validated against a bronchial challenge test, these questions had a specificity of 94.8, 99.5, and 99.7, respectively.13
Chronic bronchitis symptoms group. This group included those who responded affirmatively to both of the following two questions: Have you had a cough for more than three consecutive months over the last two years? and Have you had expectoration for more than three consecutive months over the last two years?
Minor respiratory symptoms group. This group included those who responded affirmatively to any of the following questions: Have you noticed wheezing at any time during the last 12 months, or wheezing when you had a cold? Have you woken up at night with a feeling of tightness or tension in your chest at any time during the last 12 months? Have you felt short of breath while at rest or different levels of breathlessness at any time during the last 12 months? To be included in this category, subjects had to answer one or more of these questions positively while answering in the negative to questions in the two prior groups.
Chronic cough symptoms group. This group included those who responded affirmatively to either of the following questions: Do you cough habitually during the day or night during the winter? and Do you expectorate during the day or night in winter?
Group with no respiratory symptoms. This group included those who responded negatively to all the previous questions. Four groups were formed for the smoking variable: nonsmokers were defined as individuals who never smoked or who smoked fewer than 20 packs throughout their lives. Current smokers were defined as those who smoked for at least 1 month and who continued to smoke. For current smokers, consumption was classified as 1–9 cigarettes/day, 10–20 cigarettes/day, and more than 20 cigarettes/day. Passive smokers were defined as nonsmokers who were regularly (on most days and nights) exposed to smoke over the last 12 months. Ex-smokers were defined as those who reported smoking more than 20 packs during their lives and who had quit smoking at least one month before the evaluation.
IgE and lung function
Levels of total IgE in excess of 100IU/mL were considered positive.
The lung function test consisted of forced spirometry with bell spirometers (Biomedin 9000, Padva, Italy). The spirometry equipment and technique complied with the criteria of the European Commission of Steel and Coal (ECSC)14 and that of the American Thoracic Society (ATS).15 The aim of basal spirometry was to obtain the forced expiratory volume (FEV1) and the forced vital capacity (FVC) of each individual by making up to a maximum of nine manoeuvres in each subject.
Quality control
A quality control plan for field work was designed for all the centres taking part in the survey. This plan included the supervision of each stage in the survey by an experienced specialist of the coordinating centre who visited the participating centres. Likewise, the degree of monitoring was audited on the spot by an external quality control team at least twice during the survey.
The quality control programme consisted of the external analysis (Biomedin, Italy) of 30 spirometric curves selected at random from the data bank of each centre, corresponding to different data gathering times during the course of the protocol, was applied to the spirometric equipment.
Statistical Methods
Frequencies, percentages, averages and standard deviations are presented for the main sociodemographic variables, clinical symptoms, lung function and smoking. In order to assess the differences between smoking and symptoms, the chi-square test was used when frequencies were compared. For the relationship between smoking and FEV1 and the FEV1/FVC ratio, ANOVA and the Scheffe test were used for multiple comparisons. The relationship of smoking was studied in five categories, with the presence of several respiratory symptoms adjusted according to geographic area, total IgE, age, sex, and FEV1 value. For the smoking variable, the basal comparison group was nonsmokers. Four logistic regression models were used in which the dependent variable was nonsmokers without symptoms and the comparison groups were, respectively, subjects with asthma symptoms, chronic bronchitis, minor respiratory symptoms, and chronic cough. The odds ratios (OR) and the 95% confidence intervals (CI) of each model are presented.
In order to study the relationship of the five types of smoking habit with FEV1, linear regression models were used. The dependent variables of the two models were the FEV1 and the FEV1/FVC ratio, and the independent variables, in addition to smoking, were age, geographical area, IgE, respiratory symptoms, and sex. The β coefficient of each of the smoking categories is presented, compared to the group of nonsmokers. This was considered statistically significant when p was less than 0.05. Analyses were made with Stata 7.0 (Stata Corp, College Station, TX, USA).
Results
In total, we studied 2,647 subjects. Of these, 1,372 (51.8%) were women and 1,257 (48.2%) were men, with an average age of 32 years in both genders. The subjects were evenly distributed between Barcelona, Galdakao, Albacete, Oviedo, and Huelva. Although the proportion of women was greater in Barcelona (57%) than in the rest of the centres, the difference was not statistically significant (p=0.16). With regard to groups of symptoms, minor respiratory symptoms were the most common, followed by asthma-related symptoms, habitual coughs, and chronic bronchitis (table 1). However, no symptom was the most common category. With regard to smoking, high prevalence rates were observed, with a higher proportion of smokers among men (n=735, or 55%) than among women (n=599, or 44%) (p<0.01). This is largely attributable to the fact that the number of smokers of more than 1 pack/day is higher among men than women. Among non-smokers, the majority reported regular exposure to passive smoke. More men than women had total IgE levels > 100 IU/mL.
Table 2 shows the distribution of subjects by smoking and respiratory symptoms. Non smokers represented the highest percentage of subjects without respiratory symptoms. With regard to respiratory symptoms, we observed significant differences between non-smokers and smokers, even in the group consuming 1–9 cigarettes/day.
Table 3 shows the measurements of FEV1 (ml) and the FEV1/FVC (%) according to smoking habit. Significant differences were found in the FEV1/FVC among those who smoked more than 20 cigarettes/day compared to non-smokers.
Table 4 shows the adjusted association between smoking and respiratory symptoms. The independent variable in this model was smoking, with nonsmokers providing the reference group. The results were adjusted according to geographical area, total IgE, age, sex, and FEV1, which are factors that we found to be related to the presence of respiratory symptoms. The dependent variable included patients who did not have symptoms and they were compared respectively in four models with patients with symptoms relating to asthma, chronic bronchitis, minor respiratory symptoms, and habitual coughs. After adjusting for these in accordance with the aforementioned variables, we found that smoking was associated with a greater risk of respiratory symptoms, especially chronic bronchitis. The risk of having minor respiratory symptoms and habitual cough was also observed in all groups of smokers, and the risk increased directly with the number of cigarettes/day. The risk of having minor respiratory symptoms was found even in ex-smokers. In the group of patients with asthma-related symptoms, there is a risk only in smokers of > 20 cigarettes/day.
Table 5 shows the adjusted association between smoking and lung function measured by FEV1 and the ratio of FEV1/FVC. After being adjusted for age, height, sex, geographical area, total IgE, and respiratory symptoms, we found a deterioration of both FEV1 and the FEV1/FVC ratio that was related to the number of cigarettes/day. This was statistically significant for individuals who smoked more than 10 cigarettes/day.
Discussion
Our survey demonstrates a strong association between smoking and respiratory symptoms among young adults, as well as a considerable deterioration of lung function that is directly related to the number of cigarettes smoked on a daily basis.
Although the relationship between smoking and increased risk of chronic bronchitis is well established,1 the relationship between smoking and adult asthma has not been clearly defined. This study was conducted to explore this association in a young population, as well as to investigate the connection between respiratory symptoms such as wheezing, tightness, breathlessness, or cough in young smokers, including those with low cigarette consumption, and their impact on lung function. Moreover, most previous surveys have been conducted among populations of older adults in whom the effects of smoking have accumulated over many years.
As early as the univariate analysis of our survey, a significantly higher frequency of symptoms was observed in smokers compared to nonsmokers. For the symptoms we examined, smoking was the most potent risk factor for the presence of cough and chronic expectoration. The risk of these increased with the number of cigarettes smoked each day. These findings are in line with those of a survey conducted among adolescents aged 14–18 years that demonstrated that individuals who smoked more than one pack of cigarettes per year had a higher likelihood of suffering from coughing fits (OR, 5.6) and expectoration (OR, 5.5) for more than 3 months/year than nonsmokers or those who smoked less than one pack/year. The survey also pointed out that even among those who were just beginning to smoke, smoking at least one pack/year yields a similar symptomatology as found among adult smokers with chronic bronchitis.16
An increased risk of presenting with asthma symptoms was observed only among those who smoked more than 20 cigarettes/day. Prior studies of the association between smoking and asthma have yielded conflicting results. This may be due to the fact that the relationship between smoking and asthma is likely limited by a potential bias individuals with airway hyperresponsiveness, who have a high risk of developing asthma, are less likely to be smokers and are more likely to give up the smoking habit than individuals with normal airways.2,17,18 This self-selection could explain why smokers show ‘less risk’ of asthma than non-smokers.2
Few surveys have analysed the association between smoking and other respiratory symptoms such as wheezing, dyspnea, tight chest, or cough. We found a direct association between smoking and these symptoms, and demonstrated that the risk increases in accordance with the number of cigarettes smoked per day, even among ex-smokers. Similar results were observed in a population sample of adults 20–69 years of age who smoked more than 14 cigarettes/day, with statistically significant increased risks of wheezing (OR, 3.6) and dyspnea (OR, 2.5).3 Smaller but still significant increases in risks were also observed among ex-smokers.
Our survey also showed that reductions of FEV1 were directly associated with the number of cigarettes smoked per day. A similar association was found in an analysis of a group of European subjects, although these results were not adjusted for respiratory symptoms.19 We observed a mean deterioration in FEV1 of −177 mL among those who smoked more than 20 cigarettes/day. This is similar to reductions found by other investigators. In one study, for example, individuals who smoked 25 cigarettes/day had a deterioration in FEV1 of −250 ml, regardless of whether the duration of smoking was 5 years or 40 years.20 The change in FEV1 in our study was not related to known variables such as age, height, sex, IgE, geographical area, and respiratory symptoms, and a significant deterioration was observed even among subjects with FEV1 levels > 100% more than the predicted value. This demonstrates the negative impact of smoking in a population in which the decline in lung function has barely begun and in which the cumulative effects of smoking are scarcely appreciable.
Among passive smokers, we did not find an increased risk of respiratory symptoms or a deterioration in lung function compared with nonsmokers. Previous surveys exploring this association have generated widely different results. One cross-sectional survey of a population aged 40–69 years showed an association between exposure to cigarette smoke and a decline in FEV1 and FVC level. It also demonstrated that this association was dosage dependent.21 In contrast, a longitudinal survey of a similar but slightly younger population (aged 15–40 years) did not find that exposure to cigarette smoke at home and work led to major ventilatory deterioration.22 This study did, however, demonstrate an increased risk of developing dyspnea (odds ratio: 2.37) at a mean exposure of 10 cigarettes/day, as well as a tendency to increased risk of wheezing and cough.23 The differences between these findings and ours may be due to several reasons. The cross-sectional survey was conducted among an older population and was not adjusted by the same variables that we used. The difference in symptomatology results between our study and the longitudinal study described above may be due to the longer follow-up in that study.
Our study has several limitations. In our study, as well as in many previous studies of the relationship between smoking and asthma, a potential diagnostic labelling bias on asthma patients may exist because the clinical decision to label chronic respiratory symptoms as ‘asthma’ rather than ‘chronic bronchitis’ is often influenced by knowledge of smoking habit. Thus, a non-smoker with wheeze and breathlessness is more likely to be labelled as asthmatic than a smoker with the same symptoms. Another limitation may be the sensitivity and specificity of the questionnaire used for classifying a patient as having asthma, due in part to the fact that there is no universally accepted definition of asthma in epidemiological studies.24,25 However, the questionnaire used on this study regarding differences between asthma-related symptoms and chronic bronchitis has been validated in a Spanish population and found to adequately distinguish the two.26 As with all cross-sectional surveys, ours cannot establish a causal association between smoking and respiratory symptoms or lung function, or determine whether there is any reversibility of these findings. The study design also made it impossible to establish a time value for the decline in lung function. The study's strengths include its large size, geographic heterogeneity, and the use of a standardized protocol.
The Spanish Group of the European Study is formed by the General Co-ordinator: José M. Antó. Albacete: Jesús Martínez(Moratalla, Enrique Almar, Xavier Aguilar, Mariano Arévalo, Antonio Mateos, Alberto Sánchez, Anna Teixidó and Manuel Vizcaya. Barcelona: Jordi Sunyer, Felip Burgos, Jordi Castellsagué, M. Bruna Galobardes, Joseph Roca, Joan B. Soriano and Aurelio Tobías. Galdakao: Nerea Muñiozguren, Alberto Capelastegui, Jacinto Ramos and Isabel Urrutia. Huelva: José Antonio Maldonado, José Luis Sánchez, Antonio Pereira and Jesús Grévalos. Oviedo: Félix Payo, Ramón Quirós, Julián Azofre, Luis Palenciano, G. Rego and A. Vega.
Baseline characteristics of the study populations
| . | Women . | . | Men . | . | ||||
|---|---|---|---|---|---|---|---|---|
| . | n=1372 . | % 52 . | n=1275 . | % 48 . | ||||
| Age in years mean ±SD . | 32.41±7.20 . | . | 32.19±7.50 . | . | ||||
| Height cm. mean±SD | 159±5.9 | 172±6.92 | ||||||
| Area: | ||||||||
| Albacete | 320 | 23 | 306 | 24 | ||||
| Barcelona | 292 | 21 | 224 | 17 | ||||
| Galdakao | 292 | 21 | 300 | 23 | ||||
| Huelva | 203 | 15 | 191 | 15 | ||||
| Oviedo | 265 | 19 | 254 | 20 | ||||
| Smoking habit: | ||||||||
| Non smokers | 214 | 16 | 120 | 9 | ||||
| Passive smokers | 369 | 27 | 225 | 18 | ||||
| Ex-smokers | 190 | 14 | 174 | 14 | ||||
| Smoker 1(9 cigarettes/day | 175 | 13 | 118 | 9 | ||||
| Smoker 10–20 cigarettes/day | 346 | 25 | 405 | 32 | ||||
| Smoker > 20 cigarettes/day | 78 | 6 | 212 | 17 | ||||
| Symptoms: | ||||||||
| Asthma-related symptoms | 291 | 21 | 264 | 21 | ||||
| Chronic bronchitis | 58 | 4 | 102 | 8 | ||||
| Minor respiratory symptoms | 319 | 23 | 307 | 25 | ||||
| Chronic cough | 130 | 9 | 157 | 12 | ||||
| No respiratory symptoms | 574 | 42 | 445 | 35 | ||||
| FEV1 (ml) mean±SD | 3.048±0.479 | 4.095±0.743 | ||||||
| FEV1/FVC (%) mean±SD | 83.9±6.92 | 81.74±7.23 | ||||||
| IgE > 100 UI/ml | 210 | 22 | 296 | 31 | ||||
| . | Women . | . | Men . | . | ||||
|---|---|---|---|---|---|---|---|---|
| . | n=1372 . | % 52 . | n=1275 . | % 48 . | ||||
| Age in years mean ±SD . | 32.41±7.20 . | . | 32.19±7.50 . | . | ||||
| Height cm. mean±SD | 159±5.9 | 172±6.92 | ||||||
| Area: | ||||||||
| Albacete | 320 | 23 | 306 | 24 | ||||
| Barcelona | 292 | 21 | 224 | 17 | ||||
| Galdakao | 292 | 21 | 300 | 23 | ||||
| Huelva | 203 | 15 | 191 | 15 | ||||
| Oviedo | 265 | 19 | 254 | 20 | ||||
| Smoking habit: | ||||||||
| Non smokers | 214 | 16 | 120 | 9 | ||||
| Passive smokers | 369 | 27 | 225 | 18 | ||||
| Ex-smokers | 190 | 14 | 174 | 14 | ||||
| Smoker 1(9 cigarettes/day | 175 | 13 | 118 | 9 | ||||
| Smoker 10–20 cigarettes/day | 346 | 25 | 405 | 32 | ||||
| Smoker > 20 cigarettes/day | 78 | 6 | 212 | 17 | ||||
| Symptoms: | ||||||||
| Asthma-related symptoms | 291 | 21 | 264 | 21 | ||||
| Chronic bronchitis | 58 | 4 | 102 | 8 | ||||
| Minor respiratory symptoms | 319 | 23 | 307 | 25 | ||||
| Chronic cough | 130 | 9 | 157 | 12 | ||||
| No respiratory symptoms | 574 | 42 | 445 | 35 | ||||
| FEV1 (ml) mean±SD | 3.048±0.479 | 4.095±0.743 | ||||||
| FEV1/FVC (%) mean±SD | 83.9±6.92 | 81.74±7.23 | ||||||
| IgE > 100 UI/ml | 210 | 22 | 296 | 31 | ||||
Baseline characteristics of the study populations
| . | Women . | . | Men . | . | ||||
|---|---|---|---|---|---|---|---|---|
| . | n=1372 . | % 52 . | n=1275 . | % 48 . | ||||
| Age in years mean ±SD . | 32.41±7.20 . | . | 32.19±7.50 . | . | ||||
| Height cm. mean±SD | 159±5.9 | 172±6.92 | ||||||
| Area: | ||||||||
| Albacete | 320 | 23 | 306 | 24 | ||||
| Barcelona | 292 | 21 | 224 | 17 | ||||
| Galdakao | 292 | 21 | 300 | 23 | ||||
| Huelva | 203 | 15 | 191 | 15 | ||||
| Oviedo | 265 | 19 | 254 | 20 | ||||
| Smoking habit: | ||||||||
| Non smokers | 214 | 16 | 120 | 9 | ||||
| Passive smokers | 369 | 27 | 225 | 18 | ||||
| Ex-smokers | 190 | 14 | 174 | 14 | ||||
| Smoker 1(9 cigarettes/day | 175 | 13 | 118 | 9 | ||||
| Smoker 10–20 cigarettes/day | 346 | 25 | 405 | 32 | ||||
| Smoker > 20 cigarettes/day | 78 | 6 | 212 | 17 | ||||
| Symptoms: | ||||||||
| Asthma-related symptoms | 291 | 21 | 264 | 21 | ||||
| Chronic bronchitis | 58 | 4 | 102 | 8 | ||||
| Minor respiratory symptoms | 319 | 23 | 307 | 25 | ||||
| Chronic cough | 130 | 9 | 157 | 12 | ||||
| No respiratory symptoms | 574 | 42 | 445 | 35 | ||||
| FEV1 (ml) mean±SD | 3.048±0.479 | 4.095±0.743 | ||||||
| FEV1/FVC (%) mean±SD | 83.9±6.92 | 81.74±7.23 | ||||||
| IgE > 100 UI/ml | 210 | 22 | 296 | 31 | ||||
| . | Women . | . | Men . | . | ||||
|---|---|---|---|---|---|---|---|---|
| . | n=1372 . | % 52 . | n=1275 . | % 48 . | ||||
| Age in years mean ±SD . | 32.41±7.20 . | . | 32.19±7.50 . | . | ||||
| Height cm. mean±SD | 159±5.9 | 172±6.92 | ||||||
| Area: | ||||||||
| Albacete | 320 | 23 | 306 | 24 | ||||
| Barcelona | 292 | 21 | 224 | 17 | ||||
| Galdakao | 292 | 21 | 300 | 23 | ||||
| Huelva | 203 | 15 | 191 | 15 | ||||
| Oviedo | 265 | 19 | 254 | 20 | ||||
| Smoking habit: | ||||||||
| Non smokers | 214 | 16 | 120 | 9 | ||||
| Passive smokers | 369 | 27 | 225 | 18 | ||||
| Ex-smokers | 190 | 14 | 174 | 14 | ||||
| Smoker 1(9 cigarettes/day | 175 | 13 | 118 | 9 | ||||
| Smoker 10–20 cigarettes/day | 346 | 25 | 405 | 32 | ||||
| Smoker > 20 cigarettes/day | 78 | 6 | 212 | 17 | ||||
| Symptoms: | ||||||||
| Asthma-related symptoms | 291 | 21 | 264 | 21 | ||||
| Chronic bronchitis | 58 | 4 | 102 | 8 | ||||
| Minor respiratory symptoms | 319 | 23 | 307 | 25 | ||||
| Chronic cough | 130 | 9 | 157 | 12 | ||||
| No respiratory symptoms | 574 | 42 | 445 | 35 | ||||
| FEV1 (ml) mean±SD | 3.048±0.479 | 4.095±0.743 | ||||||
| FEV1/FVC (%) mean±SD | 83.9±6.92 | 81.74±7.23 | ||||||
| IgE > 100 UI/ml | 210 | 22 | 296 | 31 | ||||
Distribution of respiratory symptoms according to smoking
| . | Asthma-related symptoms . | . | Chronic bronchitis . | . | Minor respiratory symptoms . | . | Chronic cough . | . | No respiratory symptoms . | . | P value . | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Smoking habit . | n . | % . | n . | % . | n . | % . | n . | % . | n . | % . | . | |||||
| Non smoker | 79 | 23.65 | 5 | 1.50 | 52 | 15.57 | 25 | 7.49 | 173 | 51.80 | – | |||||
| Passive smoker | 126 | 21.21 | 11 | 1.85 | 122 | 20.54 | 40 | 6.73 | 295 | 49.66 | 0.417 | |||||
| Ex(smoker | 66 | 18.13 | 9 | 2.47 | 76 | 20.88 | 24 | 6.59 | 189 | 51.92 | 0.180 | |||||
| Smoker 1-9 cigarettes/day | 59 | 20.14 | 12 | 4.10 | 64 | 21.84 | 37 | 12.63 | 121 | 41.30 | 0.003 | |||||
| Smoker 10(20 cigarettes/day | 144 | 19.17 | 67 | 8.92 | 216 | 28.76 | 123 | 16.38 | 201 | 26.76 | < 0.0001 | |||||
| Smoker > 20 cigarettes/day | 76 | 26.21 | 54 | 18.62 | 89 | 30.69 | 34 | 11.72 | 37 | 12.76 | < 0.0001 | |||||
| . | Asthma-related symptoms . | . | Chronic bronchitis . | . | Minor respiratory symptoms . | . | Chronic cough . | . | No respiratory symptoms . | . | P value . | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Smoking habit . | n . | % . | n . | % . | n . | % . | n . | % . | n . | % . | . | |||||
| Non smoker | 79 | 23.65 | 5 | 1.50 | 52 | 15.57 | 25 | 7.49 | 173 | 51.80 | – | |||||
| Passive smoker | 126 | 21.21 | 11 | 1.85 | 122 | 20.54 | 40 | 6.73 | 295 | 49.66 | 0.417 | |||||
| Ex(smoker | 66 | 18.13 | 9 | 2.47 | 76 | 20.88 | 24 | 6.59 | 189 | 51.92 | 0.180 | |||||
| Smoker 1-9 cigarettes/day | 59 | 20.14 | 12 | 4.10 | 64 | 21.84 | 37 | 12.63 | 121 | 41.30 | 0.003 | |||||
| Smoker 10(20 cigarettes/day | 144 | 19.17 | 67 | 8.92 | 216 | 28.76 | 123 | 16.38 | 201 | 26.76 | < 0.0001 | |||||
| Smoker > 20 cigarettes/day | 76 | 26.21 | 54 | 18.62 | 89 | 30.69 | 34 | 11.72 | 37 | 12.76 | < 0.0001 | |||||
p=with respect to non smokers.
p value indicate the statistically significant or not result of comparing each of the five smoking groups with the baseline smoking group: non smoker. Chi-square test employed in all cases.
Distribution of respiratory symptoms according to smoking
| . | Asthma-related symptoms . | . | Chronic bronchitis . | . | Minor respiratory symptoms . | . | Chronic cough . | . | No respiratory symptoms . | . | P value . | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Smoking habit . | n . | % . | n . | % . | n . | % . | n . | % . | n . | % . | . | |||||
| Non smoker | 79 | 23.65 | 5 | 1.50 | 52 | 15.57 | 25 | 7.49 | 173 | 51.80 | – | |||||
| Passive smoker | 126 | 21.21 | 11 | 1.85 | 122 | 20.54 | 40 | 6.73 | 295 | 49.66 | 0.417 | |||||
| Ex(smoker | 66 | 18.13 | 9 | 2.47 | 76 | 20.88 | 24 | 6.59 | 189 | 51.92 | 0.180 | |||||
| Smoker 1-9 cigarettes/day | 59 | 20.14 | 12 | 4.10 | 64 | 21.84 | 37 | 12.63 | 121 | 41.30 | 0.003 | |||||
| Smoker 10(20 cigarettes/day | 144 | 19.17 | 67 | 8.92 | 216 | 28.76 | 123 | 16.38 | 201 | 26.76 | < 0.0001 | |||||
| Smoker > 20 cigarettes/day | 76 | 26.21 | 54 | 18.62 | 89 | 30.69 | 34 | 11.72 | 37 | 12.76 | < 0.0001 | |||||
| . | Asthma-related symptoms . | . | Chronic bronchitis . | . | Minor respiratory symptoms . | . | Chronic cough . | . | No respiratory symptoms . | . | P value . | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Smoking habit . | n . | % . | n . | % . | n . | % . | n . | % . | n . | % . | . | |||||
| Non smoker | 79 | 23.65 | 5 | 1.50 | 52 | 15.57 | 25 | 7.49 | 173 | 51.80 | – | |||||
| Passive smoker | 126 | 21.21 | 11 | 1.85 | 122 | 20.54 | 40 | 6.73 | 295 | 49.66 | 0.417 | |||||
| Ex(smoker | 66 | 18.13 | 9 | 2.47 | 76 | 20.88 | 24 | 6.59 | 189 | 51.92 | 0.180 | |||||
| Smoker 1-9 cigarettes/day | 59 | 20.14 | 12 | 4.10 | 64 | 21.84 | 37 | 12.63 | 121 | 41.30 | 0.003 | |||||
| Smoker 10(20 cigarettes/day | 144 | 19.17 | 67 | 8.92 | 216 | 28.76 | 123 | 16.38 | 201 | 26.76 | < 0.0001 | |||||
| Smoker > 20 cigarettes/day | 76 | 26.21 | 54 | 18.62 | 89 | 30.69 | 34 | 11.72 | 37 | 12.76 | < 0.0001 | |||||
p=with respect to non smokers.
p value indicate the statistically significant or not result of comparing each of the five smoking groups with the baseline smoking group: non smoker. Chi-square test employed in all cases.
Distribution of the measurement of FEV1 and FEV1/FVC according to smoking habit
| Smoking habit . | n . | FEV1 (ml) . | p . | FEV1/FVC (%) . | P . |
|---|---|---|---|---|---|
| Non smoker | 334 | 3,428 | 0.02 | 83.16 | < 0.0001 |
| Passive smoker | 594 | 3,544 | ns | 84.27 | ns |
| Ex(smoker | 364 | 3,573 | ns | 82.22 | ns |
| Smoker 1–9 cigarettes/day | 293 | 3,591 | ns | 83.90 | ns |
| Smoker 10–20 cigarettes/day | 751 | 3,612 | ns | 82.42 | ns |
| Smoker > 20 cigarettes/day | 290 | 3,661 | ns | 80.39* | ns |
| Smoking habit . | n . | FEV1 (ml) . | p . | FEV1/FVC (%) . | P . |
|---|---|---|---|---|---|
| Non smoker | 334 | 3,428 | 0.02 | 83.16 | < 0.0001 |
| Passive smoker | 594 | 3,544 | ns | 84.27 | ns |
| Ex(smoker | 364 | 3,573 | ns | 82.22 | ns |
| Smoker 1–9 cigarettes/day | 293 | 3,591 | ns | 83.90 | ns |
| Smoker 10–20 cigarettes/day | 751 | 3,612 | ns | 82.42 | ns |
| Smoker > 20 cigarettes/day | 290 | 3,661 | ns | 80.39* | ns |
*Statistically significant differences between smokers > 20 cigarettes/day and non smoker, by Scheffe test.
Ns: Not statistically significant.
Non smokers were considered the baseline group. All other ‘smoking habit’ groups were compared agains the baseline group.
Distribution of the measurement of FEV1 and FEV1/FVC according to smoking habit
| Smoking habit . | n . | FEV1 (ml) . | p . | FEV1/FVC (%) . | P . |
|---|---|---|---|---|---|
| Non smoker | 334 | 3,428 | 0.02 | 83.16 | < 0.0001 |
| Passive smoker | 594 | 3,544 | ns | 84.27 | ns |
| Ex(smoker | 364 | 3,573 | ns | 82.22 | ns |
| Smoker 1–9 cigarettes/day | 293 | 3,591 | ns | 83.90 | ns |
| Smoker 10–20 cigarettes/day | 751 | 3,612 | ns | 82.42 | ns |
| Smoker > 20 cigarettes/day | 290 | 3,661 | ns | 80.39* | ns |
| Smoking habit . | n . | FEV1 (ml) . | p . | FEV1/FVC (%) . | P . |
|---|---|---|---|---|---|
| Non smoker | 334 | 3,428 | 0.02 | 83.16 | < 0.0001 |
| Passive smoker | 594 | 3,544 | ns | 84.27 | ns |
| Ex(smoker | 364 | 3,573 | ns | 82.22 | ns |
| Smoker 1–9 cigarettes/day | 293 | 3,591 | ns | 83.90 | ns |
| Smoker 10–20 cigarettes/day | 751 | 3,612 | ns | 82.42 | ns |
| Smoker > 20 cigarettes/day | 290 | 3,661 | ns | 80.39* | ns |
*Statistically significant differences between smokers > 20 cigarettes/day and non smoker, by Scheffe test.
Ns: Not statistically significant.
Non smokers were considered the baseline group. All other ‘smoking habit’ groups were compared agains the baseline group.
| . | Asthma-related symptoms . | . | Chronic bronchitis . | . | Minor respiratory symptoms . | . | Chronic cough . | . | |||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Passive smoker | 0.87 | (056–(1.36) | 0.89 | (0.25–3.09) | 1.54 | (0.93–2.54) | 1.37 | (0.67–2.80) | |||
| Ex(smoker | 0.96 | (0.58–1.59) | 1.80 | (0.50–6.48) | 1.89 | (1.09–3.28)* | 1.46 | (0.65–3.26) | |||
| Smoker 1(9 cig./day | 1.02 | (0.60–1.73) | 2.75 | (0.81–9.29) | 2.09 | (1.19–3.65)* | 2.87 | (1.36–6.05)* | |||
| Smoker 10(20 cig./day | 1.56 | (0.99–2.45) | 10.01 | (3.44–29.15)* | 3.71 | (2.26–6.11)* | 5.54 | (2.83–10.86)* | |||
| Smoker > 20 cig./day | 4.20 | (2.21–7.98)* | 47.20 | (14.64–152.20)* | 9.95 | (5.11–19.37)* | 8.37 | (3.55–19.72)* | |||
| . | Asthma-related symptoms . | . | Chronic bronchitis . | . | Minor respiratory symptoms . | . | Chronic cough . | . | |||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Passive smoker | 0.87 | (056–(1.36) | 0.89 | (0.25–3.09) | 1.54 | (0.93–2.54) | 1.37 | (0.67–2.80) | |||
| Ex(smoker | 0.96 | (0.58–1.59) | 1.80 | (0.50–6.48) | 1.89 | (1.09–3.28)* | 1.46 | (0.65–3.26) | |||
| Smoker 1(9 cig./day | 1.02 | (0.60–1.73) | 2.75 | (0.81–9.29) | 2.09 | (1.19–3.65)* | 2.87 | (1.36–6.05)* | |||
| Smoker 10(20 cig./day | 1.56 | (0.99–2.45) | 10.01 | (3.44–29.15)* | 3.71 | (2.26–6.11)* | 5.54 | (2.83–10.86)* | |||
| Smoker > 20 cig./day | 4.20 | (2.21–7.98)* | 47.20 | (14.64–152.20)* | 9.95 | (5.11–19.37)* | 8.37 | (3.55–19.72)* | |||
Odds ratios and CI of 95%, the reference group being subjects without any symptom and the reference category, those exposed to smoking habit.
Adjusted according to geographical area, total IgE, age, sex and FEV1.
*p<0.05. Compared again non smoker.
| . | Asthma-related symptoms . | . | Chronic bronchitis . | . | Minor respiratory symptoms . | . | Chronic cough . | . | |||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Passive smoker | 0.87 | (056–(1.36) | 0.89 | (0.25–3.09) | 1.54 | (0.93–2.54) | 1.37 | (0.67–2.80) | |||
| Ex(smoker | 0.96 | (0.58–1.59) | 1.80 | (0.50–6.48) | 1.89 | (1.09–3.28)* | 1.46 | (0.65–3.26) | |||
| Smoker 1(9 cig./day | 1.02 | (0.60–1.73) | 2.75 | (0.81–9.29) | 2.09 | (1.19–3.65)* | 2.87 | (1.36–6.05)* | |||
| Smoker 10(20 cig./day | 1.56 | (0.99–2.45) | 10.01 | (3.44–29.15)* | 3.71 | (2.26–6.11)* | 5.54 | (2.83–10.86)* | |||
| Smoker > 20 cig./day | 4.20 | (2.21–7.98)* | 47.20 | (14.64–152.20)* | 9.95 | (5.11–19.37)* | 8.37 | (3.55–19.72)* | |||
| . | Asthma-related symptoms . | . | Chronic bronchitis . | . | Minor respiratory symptoms . | . | Chronic cough . | . | |||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Passive smoker | 0.87 | (056–(1.36) | 0.89 | (0.25–3.09) | 1.54 | (0.93–2.54) | 1.37 | (0.67–2.80) | |||
| Ex(smoker | 0.96 | (0.58–1.59) | 1.80 | (0.50–6.48) | 1.89 | (1.09–3.28)* | 1.46 | (0.65–3.26) | |||
| Smoker 1(9 cig./day | 1.02 | (0.60–1.73) | 2.75 | (0.81–9.29) | 2.09 | (1.19–3.65)* | 2.87 | (1.36–6.05)* | |||
| Smoker 10(20 cig./day | 1.56 | (0.99–2.45) | 10.01 | (3.44–29.15)* | 3.71 | (2.26–6.11)* | 5.54 | (2.83–10.86)* | |||
| Smoker > 20 cig./day | 4.20 | (2.21–7.98)* | 47.20 | (14.64–152.20)* | 9.95 | (5.11–19.37)* | 8.37 | (3.55–19.72)* | |||
Odds ratios and CI of 95%, the reference group being subjects without any symptom and the reference category, those exposed to smoking habit.
Adjusted according to geographical area, total IgE, age, sex and FEV1.
*p<0.05. Compared again non smoker.
Association adjusted a between smoking and lung function
| . | FEV1 (ml) . | . | FEV1/FVC (%) . | . | ||
|---|---|---|---|---|---|---|
| . | Coefficient b . | p . | Coefficient b . | p . | ||
| Constant | 4,177 | 79.43% | ||||
| Passive smoker | 19 | (0.6) | 0.27 | (0.6) | ||
| Ex(smoker | –45 | (0.3) | –0.74 | (0.2) | ||
| Smoker 1–9 cigarettes/day | –22 | (0.6) | –0.25 | (0.6) | ||
| Smoker 10–20 cigarettes/day | –83 | (0.03)* | –1.23 | (0.02)* | ||
| Smoker > 20 cigarettes/day | –177 | (0.00)* | –1.51 | (0.02)* | ||
| . | FEV1 (ml) . | . | FEV1/FVC (%) . | . | ||
|---|---|---|---|---|---|---|
| . | Coefficient b . | p . | Coefficient b . | p . | ||
| Constant | 4,177 | 79.43% | ||||
| Passive smoker | 19 | (0.6) | 0.27 | (0.6) | ||
| Ex(smoker | –45 | (0.3) | –0.74 | (0.2) | ||
| Smoker 1–9 cigarettes/day | –22 | (0.6) | –0.25 | (0.6) | ||
| Smoker 10–20 cigarettes/day | –83 | (0.03)* | –1.23 | (0.02)* | ||
| Smoker > 20 cigarettes/day | –177 | (0.00)* | –1.51 | (0.02)* | ||
Adjusted according to age, height, geographical area, IgE, respiratory symptoms and sex.
Coefficient expressed as changes in ml of FEV1 and in % of FEV1/FVC and standard deviation (SD) in brackets, in comparison with those not exposed to smoking habit.
*p<0.05.
Association adjusted a between smoking and lung function
| . | FEV1 (ml) . | . | FEV1/FVC (%) . | . | ||
|---|---|---|---|---|---|---|
| . | Coefficient b . | p . | Coefficient b . | p . | ||
| Constant | 4,177 | 79.43% | ||||
| Passive smoker | 19 | (0.6) | 0.27 | (0.6) | ||
| Ex(smoker | –45 | (0.3) | –0.74 | (0.2) | ||
| Smoker 1–9 cigarettes/day | –22 | (0.6) | –0.25 | (0.6) | ||
| Smoker 10–20 cigarettes/day | –83 | (0.03)* | –1.23 | (0.02)* | ||
| Smoker > 20 cigarettes/day | –177 | (0.00)* | –1.51 | (0.02)* | ||
| . | FEV1 (ml) . | . | FEV1/FVC (%) . | . | ||
|---|---|---|---|---|---|---|
| . | Coefficient b . | p . | Coefficient b . | p . | ||
| Constant | 4,177 | 79.43% | ||||
| Passive smoker | 19 | (0.6) | 0.27 | (0.6) | ||
| Ex(smoker | –45 | (0.3) | –0.74 | (0.2) | ||
| Smoker 1–9 cigarettes/day | –22 | (0.6) | –0.25 | (0.6) | ||
| Smoker 10–20 cigarettes/day | –83 | (0.03)* | –1.23 | (0.02)* | ||
| Smoker > 20 cigarettes/day | –177 | (0.00)* | –1.51 | (0.02)* | ||
Adjusted according to age, height, geographical area, IgE, respiratory symptoms and sex.
Coefficient expressed as changes in ml of FEV1 and in % of FEV1/FVC and standard deviation (SD) in brackets, in comparison with those not exposed to smoking habit.
*p<0.05.
This study assesses the independent association of smoking with respiratory symptoms and lung function in young adults.
The risk of wheezing, tightness, short breath, habitual cough is observed in all groups of smokers.
The risk of respiratory symptoms and deterioration of FEV1 and FEV1/FVC ratio is related to the number of cigarettes/day.
This study supports the clinical repercussions of smoking among young adults in whom the cumulative effects are limitaded.
The ECRHS is financed with funds from the European Community and FIS 91/00160600E–OSE and 93/0393 subsidies.
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