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Research paper
The relationship between regular second-hand smoke exposure at home and indictors of lung function in healthy school boys in Khartoum
  1. Tarig Hakim Merghani,
  2. Amal M Saeed
  1. Department of Physiology, Faculty of Medicine, University of Khartoum, Khartoum, Sudan
  1. Correspondence to Dr Tarig Hakim Merghani, Department of Physiology, University of Khartoum, Faculty of Medicine, Khartoum 11115, Sudan; tarighm{at}gmail.com

Abstract

Background Exposure to second-hand tobacco smoke at home has been linked to many complications, including impaired lung ventilatory function; however, there is great variation in intensity of this complication between individuals of different countries. The aim of this study was to determine relationship between regular second-hand smoke exposure at home and the spirometric derived values forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), forced expiratory flow 50% and peak expiratory flow rate in healthy school boys in Khartoum.

Methods A total of 135 male school pupils were selected randomly from three governmental primary schools for boys in Khartoum. Inclusion criteria were healthy school pupil, 9–14 years old, not active smoker, either exposed regularly to cigarette smoke at home since birth or not exposed to cigarette smoke or any other type of smoke inside or outside the house. All spirometric measurements were performed using Clement Clarke All-flow Spirometer.

Results 69 school pupils were exposed regularly to second-hand smoke at home, whereas 66 pupils were not. Fathers were responsible for 67.5% of second-hand smoke at home; relatives for 30% and mothers for 2.5%. Mean FVC (±SD) was 2.21 ±0.57 l for the exposed pupils and 2.41 ±0.35 l for the non-exposed, showing reduction by about 8%. Mean FEV1 (mean ±SD) was 2.03 ±0.46 l for the exposed and 2.20 ±0.42 l for the non-exposed, indicating reduction by about 7%. The differences between the two groups were statistically significant (p<0.05).

Conclusion Regular second-hand smoke exposure at home causes significant reduction in FVC and FEV1 by about 7%–8% in school pupils in Khartoum.

  • Cotinine
  • environment
  • smoking-caused disease
  • nicotine
  • second-hand smoke

https://doi.org/10.1136/tobaccocontrol-2011-050169

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    Introduction

    Despite increasing information about the adverse health effects of smoking and bans on smoking by some governments, the use of tobacco continued to increase.1 More than 1 billion men and about 250 million women worldwide use tobacco every day.2 The developing countries are of particular focus for the tobacco companies because they have ineffective health policies and fewer resources to curb smoking.2 In the Sudan, smoking of imported and locally manufactured cigarettes is popular among many Sudanese subjects. In their cross-sectional study in 1998 in the Nile State, Idris et al 3 found that 12% of adult Sudanese men and 0.9% of adult women are cigarette smokers. According to the study, the prevalence of cigarette smoking is significantly higher in the urban areas than in the rural areas. Recent studies reported increasing prevalence of cigarette smoking among children and adolescents.4 ,5 It is well known that the percentage of second-hand smokers in a population is far higher than that of active smokers.6 ,7 In the Sudan, about 28% of school pupils live in homes where others smoke in their presence and 16.5% of all pupils have one or more parents who smoke.4 Because many young children spend a large proportion of their time indoors, they may have significant exposure to second-hand smoke at home.8

    Cigarette smoke contains over 4000 compounds, many of which are extremely reactive affecting the physiology of the respiratory system and other systems in the body.9 These include nicotine, tar, carbon monoxide and nitrogen oxides. They induce inflammation within the airways and reduce oxygen-carrying capacity of the blood. Inflammation of the airways results in increased mucus production, decreased ciliary movement and increased mucosal permeability to allergens.

    A growing body of scientific evidence indicates that childhood exposure to second-hand smoke adversely affects lung function.10 Several studies suggested that pulmonary function decrement in school-aged children was a result of combined early life (including intrauterine life) and current exposure to parental smoking, especially the maternal smoking.11 ,12 However, the negative effect of second-hand smoke on lung function is amplified in children with residual lung insult due to asthma, cystic fibrosis or other lung disease.13 ,14 Intrauterine exposure to maternal smoking was associated with a large deficit in lung functions in children with asthma. This deficit was found to be independent of the effects of postnatal second-hand smoke exposure. Occasional low level of exposure to cigarette smoke seems to be associated with lung function alterations in adolescents.15 On the other hand, some studies reported that intrauterine exposure had no effect, suggesting that exposure to second-hand smoke after birth represents a major contributing factor to development and persistence of airflow obstruction or respiratory symptoms.16–18

    Effects of cigarette smoke on lung function in children can be assessed by measuring the spirometric parameters forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), ratio of FEV1/FVC (FEV1/FVC%), forced expiratory flow 50% (FEF50%) and the peak expiratory flow rate (PEF). These parameters are used for diagnosis of obstructive and restrictive lung diseases. Most children from age 9 years and older met adult-based American Thoracic Society (ATS) goals for spirometry test performance.19 The aim of this study was to determine the relationship between regular second-hand smoke exposure at home and FEV1, FVC, FEF50 and PEF in healthy school boys in Khartoum, Sudan.

    Methods

    Study area and population

    This is a cross-sectional study conducted in three governmental primary schools for boys in Khartoum in the year 2009. The schools were selected randomly from 92 primary schools, the total number of public schools for boys in Khartoum. Parents of the pupils were generally of the average socioeconomic class. They lived in houses near the schools of their children. Most of the fathers were manual workers or employees, whereas the majority of the mothers were housewives.

    Sample size

    The total number of pupils in the three schools was 573. According to inclusion and exclusion criteria, 135pupils were selected.

    Inclusion and exclusion criteria

    Inclusion criteria were school pupil, aged 9–14 years, healthy with normal body mass index (BMI), has no symptoms or signs of acute or chronic medical illness during the past 4 weeks, no signs of respiratory disease or chest deformity, not on medical treatment, not active smoker and either exposed regularly to cigarette smoke of not less than two cigarettes per day for most days since birth at home or not exposed to second-hand smoke or any other type of smoke inside or outside the house. Exclusion criteria were age younger than 9 years or older than 14 years, abnormal BMI, presence of symptoms of acute or chronic medical illness during the past 4 weeks, history of atopy, presence of abnormal chest signs or skeletal deformity on clinical examination, being on medical treatment, active smoker, exposed to smoke of less than two cigarettes per day inside the house or any other type of smoke inside or outside the house.

    Methods of data collection

    Questionnaire

    Each school pupil was visited at home and interviewed on presence of his parents to answer questions about his age, class, school performance, health problems, smoking habits, exposure to second-hand cigarette smoke at home or outside the house, frequency of exposure, exposure to any other type of smoke in or outside the house, number of smokers in the house and who is a smoker.

    Evaluation of the degree of exposure

    According to the information obtained from each pupil, pupils with regular second-hand smoke exposure were subdivided into two groups: mild–moderate exposure (exposed to smoke of two to five cigarettes per day) and group of heavy exposure (exposed to smoke of more than five cigarettes per day).

    Clinical examination

    Each pupil was examined physically to exclude the presence of any abnormal clinical sign that might interfere with the normal function of his respiratory system, such as pleural effusion, pneumothorax, asthma and signs of chest deformity or skeletal abnormality. Height and weight of each pupil were measured using standardised height and weight scales. The BMI was calculated for each pupil as weight (in kilogrammes)/height2 (in metres). The BMI results were compared to normal values of BMI adjusted for age and sex.20

    Spirometry

    A portable All-flow spirometer (Clement Clarke International, Harlow, UK) was used to measure FVC, FEV1, FEF50 and PEF for each pupil. Measurements were carried out according to the guidelines of the ATS.21

    Measurement steps

    1. Air temperature and relative humidity of the room were measured and registered in a computer program that controls the spirometer.

    2. The spirometer was calibrated with a 3 l calibrating syringe.

    3. The age, sex, height and weight of each pupil were registered in the computer program.

    4. Each pupil was asked to stand up, clip his nose with a nose clip, take a deep breath, put a mouthpiece connected to the spirometer in his mouth with the lips tightly around it and then blow air out as hard and as fast as possible for at least 6 s.

    5. The procedure was repeated according to the ATS criteria (mentioned above) until acceptable and reproducible results were obtained.

    6. Total measurement trials for each pupil did not exceed eight times to avoid exhaustion.

    Ethical consideration

    The research conforms to the ethical principles of medical research developed by the World Medical Association Declaration of Helsinki.22 Ethical approval was given by the Research Committee (Faculty of Medicine/University of Khartoum). Approval was obtained from the Unit of School Health/Ministry of Education. Permission letters were submitted to the headmasters of the selected schools. Written consents were obtained from the parents before entry into the study.

    Statistical analysis

    Data obtained with questionnaire and spirometry were analysed using the Statistical Package for the Social Sciences V.16 (SPSS Inc.). The independent Student t test was used for comparison between second-hand smokers and non-smokers regarding their physical characteristics (age, weight, height and BMI) and the mean values of spirometric parameters FVC, FEV1, FEF50 and PEF. Statistical significance was accepted when p value was less than 0.05.

    Results

    Characteristics of pupils in the study group

    No significant difference was found between pupils with regular second-hand smoke exposure at home and those without exposure in distribution of age, height, weight and BMI (table 1).

    View this table:
    Table 1

    Mean age, height, weight and BMI among school pupils in the study group

    Sources of second-hand smoke in the study group

    Fathers were responsible for about 67% of in the group of second-hand smokers; mothers were responsible for more than 2%, whereas relatives like brothers and uncles were responsible for about 30% (figure 1).

    Figure 1
    Figure 1

    Sources of second-hand smoke in the study group. Parents are responsible for 70% of second-hand smoke at home, whereas close relatives are responsible for 30%.

    Effect of second-hand smoke exposure on spirometric derived values

    The mean FVC was lower in the group of second-hand smokers (2.21±0.57 l) than the group of non-smokers (2.41±0.35 l) by about 8%, and the mean FEV1 was lower in the group of second-hand smokers (2.03±0.46 l) than the non-smokers (2.20±0.42 l) by about 7%. The differences between the two groups were statistically significant (p<0.05) (table 2). Analysis of the dose of exposure to cigarette smoke showed insignificant difference in all parameters (FVC, FEV1, FEF50 and PEF) between non-smokers, second-hand smokers with mild–moderate exposure and second-hand smokers with heavy exposure (table 3).

    View this table:
    Table 2

    Mean spirometric derived values among school pupils in the study group

    View this table:
    Table 3

    Distribution of mean spirometric values according to dose of cigarette smoke exposure

    Discussion

    Pulmonary function tests are important tools for diagnosis and follow-up of many respiratory problems. Abnormalities may appear even if the patient is asymptomatic. Spirometry is the most commonly used test in assessment of lung ventilation. It detects presence of airflow obstruction or lung restriction, evaluates severity, aids in the differential diagnosis of respiratory illness, assesses disease progression and evaluates response to treatment. The effects of second-hand smoke on ventilatory functions of the lung in children and adolescents were assessed in many studies worldwide. The results of these studies were controversial. Some studies found significant association between second-hand smoke and impaired lung function,23–25 whereas others did not.26–28 Some studies reported sex differences in vulnerability to the negative effects of second-hand smoke, with women being affected more than men; others reported different results and related the negative effects to maternal smoking rather than paternal smoking.29 ,30 The variation in the effect of second-hand smoke on lung function in children at the school age may be related to differences in genetic factors or variation in environmental factors, lifestyles and housing conditions of different communities. In a comparative study of lung function in relation to second-hand smoke exposure between American and French women, second-hand smoke exposure was found to be significantly related to lower FVC and FEV1 values among the French women but not among the American ones.31 In this study, the mean spirometric derived values (FVC, FEV1, FEF50 and PEF) were all lower in children exposed to tobacco smoke pollution at home than those who were not exposed. The significant reduction in FVC and FEV1 (by 7%–8%) suggests that second-hand smoke exposure did have negative effects on lung function of Sudanese children. Genetic vulnerability of the children and inadequate ventilation of their housing environment may explain these results. The vulnerability of Sudanese subjects to the adverse effects of respirable particles such as cotton dust, flour dust and other particles on the lungs was confirmed in many previous studies.32–36 On the other hand, inadequate ventilation prevents exchange of the indoor air, which is saturated with tobacco smoke, with the outdoor air. This exchange is supposed to decrease the concentration of gases and particulates of tobacco smoke, such as nicotine, polyacrylic hydrocarbons, carbon monoxide, acrolein and nitrogen dioxide, thus lowering the negative effects of second-hand smoke on lung function; however, the inadequate ventilation needs another study to be confirmed. Although FVC and FEV1 values were lower in children with high dose of exposure than those with no or with mild–moderate exposure, the difference was not statistically significant. A significant difference is more likely with more excessive paternal smoking, such as 30 cigarettes per day or more.37 The inflammatory process induced by cigarette smoke causes narrowing of the airways and therefore reduction in the spirometric parameters (FEF50 and PEF). In this study, although these parameters were lower among second-hand smokers than non-smokers, the difference was not statistically significant. A larger sample size might be needed to obtain significant results. Previous studies showed variable results in response to maternal smoking especially during pregnancy.11 ,12 Our results show that maternal smoking is a rare practice in the Sudan.

    The findings of this study confirm the negative effect of regular second-hand smoke exposure at home on respiratory health of Sudanese boys. Although attitudes of parents and relatives towards smoking in front of girls are not investigated, it is a well-known practice in this country that they smoke in front of boys, not girls. There is paucity of data regarding effects of tobacco smoke pollution on respiratory health of both female children and adults. That is an open area of research, especially with the recent increase in prevalence of female smoking in the Sudan. In this study, interviewing the pupils with their parents might be effective in reducing the recall bias. It is worth noting that, objective measurement of tobacco smoke exposure by cotinine detection in body fluids may not be specific for second-hand smoke exposure because dietary nicotine (eg, green pepper, tomato and tea) may elevate cotinine levels.38 ,39

    Educational programmes are highly recommended to increase awareness of parents about the respiratory health of their children. These programmes may encourage parents to stop smoking or at least teach them how to protect their children from tobacco smoke pollution.

    What is already known on this subject

    Childhood exposure to tobacco smoke pollution adversely affects lung function; however, genetic factors appear to play a role.

    What this study adds

    The significant reduction in lung function among large proportion of school pupils in Sudan is likely to be related to regular exposure to second-hand smoke at home.

    Acknowledgments

    We are very grateful to the German Academic Exchange Service (DAAD) for the scholarship grant. We would like to thank the Unit of School Health of the Ministry of Education and the school teachers for their kind permission and close supervision during the process of data collection. We would like to extend our appreciation and special thanks to the pupils and their families for their understanding and cooperation.

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    View Abstract

    Footnotes

    • Funding This work was supported by German Academic Exchange Service ‘DAAD’ grant number (section 413, Code No.: A/07/09076; Budgetary: 334400109).

    • Competing interests None.

    • Patient consent Written consents were obtained from the parents before entry into the study.

    • Ethics approval The study was approved by Research Committee, Faculty of Medicine, University of Khartoum, Sudan.

    • Provenance and peer review Not commissioned; externally peer reviewed.