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 Table of Contents  
Year : 2017  |  Volume : 24  |  Issue : 2  |  Page : 107-113

Prevalence and factors associated with exercise-induced bronchospasm among rural school children in Ilesa, Nigeria

1 Department of Paediatrics, Wesley Guild Hospital, Ilesa; Department of Paediatrics and Child Health, Obafemi Awolowo University, Ile-Ife, Nigeria
2 Department of Paediatrics, Wesley Guild Hospital, Ilesa, Nigeria

Date of Web Publication24-Jul-2017

Correspondence Address:
Bankole Peter Kuti
Department of Paediatrics and Child Health, Obafemi Awolowo University, Ile-Ife
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/npmj.npmj_46_17

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Background: Exercise-induced bronchospasm (EIB) assessed using changes in peak expiratory flow rates (PEFRs) to free range exercise is a relatively cheap way of screening for asthma in resource-poor centres where children with asthma are often undiagnosed and poorly managed. This study sets out to determine the prevalence and factors associated with EIB among rural schoolchildren in Ilesa, Nigeria. Subjects and Methods: Children aged 8–16 years from two middle schools in rural Ilesa were selected by multistage sampling. Their sociodemographic characteristics and personal/family history of asthma and allergies were obtained. The children had their PEFR measured before, 5, 10 and 15 min after 6–8 min of free running exercise to achieve 80% of their maximal pulse rate. EIB was defined as change in PEFR expressed as a percentage of the pre-exercise value ≥15%. The prevalence and factors associated with EIB were determined. Results: The mean (standard deviation) age of the 250 study participants was 12.5 (1.5) years (M: F 0.9:1) None of the children had previously been diagnosed with asthma. The prevalence of EIB was 9.2%, 6.4% and 4.0% at 5, 10 and 15 min post-exercise, respectively. Household poultry birds, personal history of allergies, wheeze in the past 12 months and family history of asthma were associated with EIB (P < 0.05); only wheezing in the past 12 months independently predicted EIB (odds ratio = 6.343; 95% confidence interval = 2.040–8.798; P= 0.020). Conclusion: The prevalence of EIB among rural schoolchildren in Ilesa was 9.2%. EIB was associated with the history of allergies and wheeze and presence of household poultry birds. We recommend routine screening of these children for early diagnosis and good asthma symptom control.

Keywords: Exercise-induced bronchospasm, peak expiratory flow rate, rural, schoolchildren

How to cite this article:
Kuti BP, Kuti DK, Omole KO, Mohammed LO, Ologun BG, Oso BI. Prevalence and factors associated with exercise-induced bronchospasm among rural school children in Ilesa, Nigeria. Niger Postgrad Med J 2017;24:107-13

How to cite this URL:
Kuti BP, Kuti DK, Omole KO, Mohammed LO, Ologun BG, Oso BI. Prevalence and factors associated with exercise-induced bronchospasm among rural school children in Ilesa, Nigeria. Niger Postgrad Med J [serial online] 2017 [cited 2020 Nov 28];24:107-13. Available from: https://www.npmj.org/text.asp?2017/24/2/107/211460

  Introduction Top

Childhood asthma is a leading cause of chronic respiratory disorder in children and a major cause of school absenteeism and poor quality of life of children and their parents.[1],[2] The International Study of Asthma and Allergic Conditions in Children (ISAAC) using standardised questionnaire puts the prevalence of asthma in school-age children as 1.6%–36.8%, with reported higher prevalence in urban areas of developed countries than rural areas of developing countries.[3] Recent studies, however, have reported an increasing prevalence of childhood asthma in developing countries of Africa including rural areas of these countries.[4],[5],[6] This increasing prevalence had been attributed among other factors to increasing urbanisation and adoption of Western lifestyles in many African settings.[4],[5],[6]

Apart from the use of standardised questionnaires in the epidemiological study of childhood asthma, the determination of ventilatory responses to exercise known as exercise-induced bronchospasms (EIBs) is also an important objective tool in screening children for asthma.[7] EIB has been reported to occur in up to 90% of children with asthma [8],[9] and has been widely used to assess childhood asthma in urban and rural African children with variable reported prevalence.[10],[11],[12] The widely variable reported prevalence of childhood EIB has been ascribed to the differences in the diagnostic device and criteria used, the environmental and climatic conditions of the study sites and the type and intensity of the provocative exercise the children underwent.[7],[8],[9]

With increasing prevalence of childhood asthma even in rural areas of developing countries where hitherto undernutrition and infectious diseases predominate,[13] coupled with the paucity of reports about childhood EIB in Nigeria, this study sets out to determine the prevalence and factors associated with EIB among rural schoolchildren in Mukoro community in Ilesa, Nigeria. This will serve as an important step in screening for childhood asthma in the community. This may also facilitate prompt diagnosis and management of childhood asthma to ensure good symptom control and improved quality of life.

  Subjects and Methods Top

Ethical consideration

Ethical approval from the Institute of Public Health, Obafemi Awolowo University, Ile-Ife, Nigeria (HREC approval no. IPH/OAU/12/254; approval date: 31st October 2014 to 26th October 2015) was obtained to carry out this study. Parental consent and assent from the children were obtained. The permission and approval of the principals and head teachers of the participating schools were also obtained. The permission of the local educational authority was also obtained for this study.

Study design

This was a school-based, descriptive cross-sectional study.

Study location

This study was conducted in two middle schools in a rural community of Ilesa West Local Government Area, South West Nigeria over a 3-month period (1st June to 31st August, 2015). Ilesa is situated on latitude 7°35'N of the equator and longitude 4°51'E of the meridian and is the largest town in Ijesaland.[14] Mukoro is a rural community in Ilesa with a primary health centre and limited access to basic social amenities. The people of Mukoro are mainly peasant farmers, petty traders and artisans.

Sample selection

Multistage sampling method was used to select the study participants: Ilesa has two local government areas (LGAs) - West and East. Ilesa West was chosen by simple random method. Ilesa West LGA has 11 public schools and 13 private schools.[15] Four of the 11 public schools are located in rural areas of the LGA. Two schools were selected randomly from the four public schools. These schools are in the Mukoro rural community of the LGA. Each of the two selected schools has five arms of classes (primary 5 to junior secondary 3), and each arm has only one stream with about 30–35 students. Seven classes were randomly selected from the total of ten classes in the two selected schools. The children in the selected classes were then recruited till the required sample size was achieved. Inclusion criteria for this study were apparently healthy children who were able to perform satisfactory peak expiratory flow rate (PEFR) measurements. Children with mental subnormality who could not follow instructions were excluded from this study. Children who could not engage in physical activities for health and other reasons and those whose parents/caregivers did not give consent to participate in the study were also excluded from the study.

Sample size determination

The minimum sample size for this study was estimated using Fisher's formula. With reference to 18.4% prevalence of EIB among rural schoolchildren from previous study [10] and 5% significant level with power of 80%, a minimum sample size of 222 study participants were estimated. Adding 10% of the calculated sample size because of the children who may not perform a satisfactory PEFR, a total of 250 children were recruited for the study.

Study procedure

Interviewer's administered pre-tested questionnaires modified from the ISAAC questionnaire were used to obtain information from the study participants. Information obtained included sex, age and tribe. Households with three or more adults sharing the same bedroom with the child were regarded as overcrowded homes.[16] Ranked assessment of parental highest level of education and occupation was done to determine the socioeconomic class to which the study participants belong as described by Oyedeji.[17]

The type of fuel used for household cooking, heating and lighting was also ascertained and recorded. Electricity and cooking gas were classified as clean fuel while firewood, coal and kerosene were classified as unclean fuel.[18] The history of whether the family rears domestic animals, pets and poultry in the household as well as the presence of cigarette smokers in the house was also obtained. Personal and family history of wheeze and a history of recurrent wheeze in the past 12 months were also obtained. Also of interest was the history of allergic diseases including recurrent nasal discharges, sneezing and blocked nostrils in response to allergens and the presence of pruritic vesicular, weeping or crusting eruptions found mostly in large joint flexures. A history suggestive of allergic conjunctivitis i.e., recurrent itchy brownish eyes, periorbital darkening and Dennis–Morgan folds was also noted.

The children were then examined for features of allergic diseases such as allergic dermatitis, rhinitis and conjunctivitis. Their pulse rate at rest and after exercise was also recorded, likewise their anthropometric measurements were recorded. Body mass index (BMI) (in kg/m 2) was calculated from the following formula: (weight in kg)/(height in m)2. The nutritional status of the children was determined by comparing their anthropometric parameters with those from the WHO growth reference chart.[19] Stunting and severe stunting were defined as height for age <15th and 3rd centiles, respectively. Underweight was defined as BMI <15th centile and overweight as BMI >85th centile on the WHO growth reference chart.[19]

All the study participants then had PEFR measured using mini Wright Peak Flow Meter (PFM) (Clement Clarke International Ltd., Airmed House, Edinburgh Way, Harlow, Essex CM20 2TT, UK) following manufacturer's instruction.[20] The mini Wright PFM has an accuracy of ± 5% and a range reading of 60–800 L/min.[20] The procedure was done in the morning from 10:00 am to 12:00 noon every day. After explaining and demonstrating the procedure to the children, with the children standing, they were instructed to inhale to their maximum capacity (total lung capacity) and then forcefully exhale into the PFM. This was done before exercise (pre-exercise PEFR) and then the children were required in batches of four children to run around the school field for 6–8 min. Each batch of four children was timed by four study assistants using a whistle and their pulse rates were checked immediately after the exercise session to ensure whether the children achieved a pulse rate of 80% of their maximal pulse rate (estimated to be 220 minus age in years).[21] The PEFR of the children was then measured again at 5, 10 and 15 min post-exercise. Each child had three measurements done at rest, 5, 10 and 15 min and the highest of the measurement was documented as the measured PEFR.

Definition of exercise-induced bronchospasm

For this study, EIB was defined as the greatest decrease in PEFR following exercise expressed as a percentage of the baseline PEFR (decrease in PEFR/baseline PEFR × 100). A positive response to exercise was defined as a decrease in PEFR of 15% or greater (EIB positive).[1] EIB positive was determined at 5, 10 and 15 min for each participant. The time duration with the highest prevalence of EIB which was at 5 min post-exercise was used for further analysis.[8],[9]

Data analysis

This was done using Statistical Program for Social Sciences (SPSS) software Version 17.0 (SPSS Inc., Chicago, IL, USA, 2008). The prevalence of EIB at 5, 10 and 15 min post-exercise was calculated from the proportion of children with EIB at those periods over the total number of the study participants. Continuous variables such as ages, weight, height, BMI and PEFR were tested for normality using Kolmogorov–Smirnov statistics at level of significance of 0.05. These were summarised using mean and standard deviations (SDs) for normally distributed variables. Proportions and percentages were determined for categorical variables such as sex and age categories. Differences between the means (SD) of continuous variables were analysed using Student's t-test or analysis of variance whereas categorical variables were analysed using Pearson's Chi-square test or Fisher's exact test, as appropriate. Binary logistic regression analysis was used to determine the independent predictors of EIB. Level of significance at 95% confidence interval was taken at P< 0.05.

  Results Top

Sociodemographic and general information about the study participants

Sex and age distribution

[Table 1] highlights the general information and sociodemographic characteristics of the children. There were 117 (46.8%) males, with male-to-female ratio of 0:9.1. The mean (SD) age was 12.5 (1.5) years and 167 (66.8%) children were in the age range of 11–13 years.
Table 1: Sociodemographic characteristics of the study participants (n=250)

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The study participants were mainly Yorubas which is the predominant ethnic group in the study site. Other ethnic groups represented are highlighted in [Table 1].

Parental socioeconomic class

Majority (60.0%) of the children were from low socioeconomic class and 40% were from middle social class.


Most (92.0%) of the children were Christians, while 8% were Muslims.

Overcrowded household

About one-half (50.4%) of the study participants lived in overcrowded homes.

Household animals and pets

One hundred and twenty-six (50.4%) children live with one animal/pet or more in their households. These included dogs 28 (11.2%), poultry birds 75 (30.4%), cat 1 (0.4%) and goats and sheep 22 (8.8%).

Exposure to cigarette smoke

Only four (1.6%) study participants live in a house with at least one person who smokes cigarette.

Household cooking fuel

Households of 34 (14.4%) children use clean fuels for household cooking, lighting and heating. One hundred and sixty (64.0%) households use kerosene and 54 (21.6%) depended on biomass fuel, mainly firewood, as their source of cooking, lighting and heating.

Personal and family history of asthma and allergic diseases among the children

None of the children recruited for this study had been previously diagnosed with asthma or currently on any asthma medications. Furthermore, only 3.2% attested to having had at least one episode of wheeze in the past 12 months. [Table 2] shows that ten (4.0%) children had a close relative ( first-degree relative, mainly parents and siblings) with allergic disease including six (2.4%) with close relative with a history of asthma.
Table 2: Personal and family history of asthma and allergic diseases and nutritional status of the study participants (n=250)

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Anthropometric parameters of the study participants

Weight and height

The mean (SD) weight of the children was 16.0 (2.2) kg. This ranged from 10.2 to 23.7 kg. Their mean (SD) height was 1.5 (0.1) m, which ranged from 1.2 to 1.7 m.

Body mass index

The BMI of the children ranged from 17.0 to 58.0 kg/m 2 with a mean (SD) of 34.2 (7.8) kg/m 2.

Nutritional status of the study participants

Over one-half (56.8%) of the children had one or more types of malnutrition [Table 2]. These included stunting (22.8%), underweight (30.8%) and overweight (3.2%). None of the study participants was obese.

Pre- and post-exercise peak expiratory flow rate of the study participants

The pre-exercise PEFR ranged from 100 to 420 L/min with a mean (SD) of 247.3 (60.0) L/min. The means (SD) of post-exercise PEFR of the children are highlighted in [Table 3]. There was no significant difference in the mean (SD) PEFR of the children before and after exercise (F = 0.269; P= 0.605).
Table 3: The pre- and post-exercise peak expiratory flow rates of the children

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Exercise-induced bronchospasm at 5 min post-exercise

Twenty-three (9.2%) of the 250 children had EIB 5 min post-exercise. This reduced to 6.4% at 10 min and 4% at 15 min post-exercise.

Factors associated with the presence of exercise-induced bronchospasm among the study participants

[Table 4] and [Table 5] highlight the sociodemographic, nutritional and other factors related to the presence of EIB among the study participants.
Table 4: Sociodemographic and general characteristics of the children as related to the presence and absence of exercise-induced bronchospasm at 5 min

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Table 5: Personal/family history of allergy and nutritional status of the children as related to exercise-induced bronchospasm at 5 min

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Children whose households rear poultry were found to be at an increased risk of having EIB as 13 (17.3%) of the 75 children with poultry animals in the household compared to 10 (6.6%) of the remaining 152 children without poultry birds in their household had EIB at 5 min (χ2 = 8.485; P= 0.040). No other sociodemographic features or housing condition were significantly associated with having EIB.

Children with a previous history of wheeze were significantly more likely to have EIB as 3 (37.5%) of the eight children with previous history of wheeze compared to 20 (8.3%) of the remaining 242 children without a previous history of wheeze had EIB (χ2 = 4.958; P= 0.026). Personal history of allergy and history of asthma in a close relative were significantly associated with the children having EIB (66.6% vs. 7.8%, respectively; χ2 = 12.448; P< 0.001).

The factors significantly associated with EIB were further analysed using binary logistic regression for the dichotomised outcome of presence or absence of EIB. Only history of wheeze in the past 12 months independently predicted the presence of EIB among the study participants as shown in [Table 6].
Table 6: Predictor of exercise-induced bronchospasm among the rural schoolchildren using binary regression analysis

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  Discussion Top

This study has highlighted the prevalence and factors associated with EIB among schoolchildren in rural areas of Ilesa, Nigeria. The prevalence of 9.2% observed in this study was similar to 10.0% reported among rural children in Manitoba [22] and 8.3% reported among rural Ghanaian children,[6] but was much higher than 6.0% reported by Onazi et al.[11] among schoolchildren in Gusau, North-West Nigeria. The difference in the prevalence of EIB from the present study compared to that of Onazi et al.[11] may be related to difference in the ages of the study participants. While this study was carried out among middle schoolchildren with a mean (SD) age of 12.5 (1.5) years, the study by Onazi et al.[11] was carried out among much younger primary schoolchildren with a mean (SD) age of 10.0 (2.2) years. The changes in asthma prevalence with age [1] may partly explain this difference in prevalence. In addition, climatic and environmental factors may also account for the difference in the prevalence of EIB observed between the two studies. While the present study was carried out among rural schoolchildren in South-West Nigeria with wet and relatively humid climate, the study of Onazi et al.[11] was carried out among children in North-West Nigeria with dry hot climate.[11] Relatively cold air had been reported to provoke more bronchospasm resulting in more reduction in PEFR than hot air.[22]

It is noteworthy from this study that none of the study participants had previously been diagnosed asthmatic. The zero prevalence of known asthmatics among the rural children was in agreement with very low prevalence of <1.0% diagnosed asthmatics in a rural population reported by Oviawe [23] in South-South Nigeria and 1.25% prevalence of asthma reported by Zhu et al.[24] from rural areas of Beijing, China. The relatively low prevalence of self-reporting asthma symptoms in rural areas may be related to poor perception of rural children and their caregivers about asthma and EIB.[25] In addition, poor access to asthma care health services where the disease may have been promptly recognised and managed during which the children and their caregivers would have been enlightened about it [1],[26] may also explain the low prevalence of self-reported asthma noted in this study. This calls for the need to make qualitative asthma care services widely available and affordable to children, particularly in rural areas for improved lung health.

Despite the absence of self-reported asthma among the children, 3.2% reported a previous history of wheezing in the past 12 months and this was found to independently predict the presence of EIB among the children. This report was corroborated with similar reports by Ng'ang'a et al.[10] from Kenya and Onazi et al.[11] from Nigeria. The presence of wheeze in the past 12 months was used in the ISAAC studies [3] to estimate the global burden of childhood asthma. Furthermore, 4.0% reported family history of asthma which was significantly associated with the presence of EIB among the children. Burke et al.[27] in the USA reported that family history of asthma in one or more first-degree relatives in their study population was a definite risk factor for childhood asthma.[27] Since the prevalence of EIB is closely related to the presence of asthma,[8],[9] one can infer that family history of asthma may increase the risk of having EIB as observed in this study. This implies that children with family history of asthma should be evaluated carefully as part of routine medical examination of the school health programme for the disease and should be promptly diagnosed and managed or referred appropriately when present.

In the present study, the personal history of allergic disease was significantly associated with EIB among the children. This was reported by other workers,[10],[11],[12] which may be related to the fact that allergic diseases such as dermatitis, conjunctivitis and rhinitis are often associated with childhood bronchial asthma in the so-called 'atopic march'.[28] This atopic march has been corroborated by van der Hulst et al.[29] in a systematic review of 13 prospective cohort studies. They concluded that children with atopic dermatitis (AD) are 2–3 times more likely to have asthma compared to those without AD. The lack of dermal integrity seen in children with AD leading to increased colonisation by bacterial superantigens had been proposed to begin the process of allergic sensitisation in the atopic march.[30] This increased bacterial colonisation induces systemic Th2 immunity that predisposes patients to allergic nasal responses and promotes airway hyperreactivity.[30] This implies that children with atopic diseases should be evaluated for asthma and promptly managed if present.

The presence of poultry birds in the household was significantly associated with EIB among the children. This may be related to the fact that exposure to poultry droppings and danders by the children predisposes them to various allergenic antigens that can trigger and induce asthmatic exacerbations. This finding was corroborated by reports of Zuskin et al.[31] where exposure to poultry birds reduces the lung capacities of study participants and predisposes them to respiratory diseases. Protecting children from being exposed to poultry birds and their droppings may go a long way in ensuring a better childhood lung health.

The present study used simple and relatively cheap device to assess the PEFR as a measure of the lung functions of the children. This device (mini Wright PFM) is easy to use and does not require much training and expertise to interpret.[20] This makes it easy for even the school teachers or school nurses to use as a screening test for asthma among the schoolchildren as part of school health programme. We, however, appreciate the limitation that the mini Wright PFM is effort dependent and may not be as reliable as using a standard spirometer for lung function assessment.[7],[8],[9] In the present study, the schoolchildren freely ran around the school field (standardised with significant increase in their pulse rate post-exercise) as the means of precipitating bronchospasms. This free range exercise has been reported to be more asthmogenic than the use of bicycle ergometer and step ladder exercise.[32] The free range running exercise unlike the other forms of exercise mimics the natural physical activities the children engage in daily.[7],[9],[32] This again constitutes the strengths of this study. We further appreciate the limitation that the environmental conditions such as relative air humidity and ambient temperature which may variably affect the lung function parameters [22] could not be controlled in this study. Nevertheless, the performance of the test at the same period of the day (10:00 am and 12:00 noon) during the course of the study helped reduce the effect of weather changes on the measured PEFR.

  Conclusion Top

The prevalence of EIB among rural schoolchildren in Mukoro, Ilesa, was 9.2%. Household triggers such as poultry birds, personal and family history of asthma and allergies were significant risk factors. The history of wheeze in the past 12 months independently predicts EIB. We recommend reduction of contact of children with poultry birds as much as possible. Routine exercise challenge test for schoolchildren with the above history as part of pre-entrance school evaluation by school health workers is also recommended. This will facilitate early diagnosis and appropriate management of childhood asthma in the rural setup.


The authors acknowledge with thanks the house officers who assisted in data collection, the principals and head teachers of the selected schools for giving their permission for the conduct of the study. They also acknowledge the parents of the study participants who gave consent for their children/wards to participate in the study and the children who enthusiastically participated in the study.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]

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[Pubmed] | [DOI]


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