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 Table of Contents  
Year : 2017  |  Volume : 4  |  Issue : 3  |  Page : 130-136

Epidemiology of pediatric asthma in a Nigerian population

1 Department of Paediatrics, Jos University Teaching Hospital, Jos, Plateau State, Nigeria
2 Department of Paediatrics, Aminu Kano Teaching Hospital, Kano, Nigeria
3 Department of Paediatrics and Child Health, University of Ilorin/University of Ilorin Teaching Hospital, Ilorin, Kwara State, Nigeria

Date of Submission30-Nov-2016
Date of Acceptance24-Jun-2017
Date of Web Publication6-Oct-2017

Correspondence Address:
Helen Oluwadamilola Akhiwu
Department of Paediatrics, Jos University Teaching Hospital, Jos, Plateau State
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jhrr.jhrr_114_16

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Background: Reports have identified a rising prevalence of bronchial asthma, with the highest pediatric burden in the 6–11 years old. Aim: This study aimed at determining the epidemiology of asthma among primary school pupils, aged 6–11 years in Kano metropolis. Settings and Design: This study was prospective, descriptive, cross-sectional study carried out among 811 primary school pupils in Kano metropolis from October 2012 to December 2013. Materials and Methods: Information was obtained using pretested questionnaires, and enlisted pupils had their spirometric values recorded. Diagnosis of asthma was based on two or more of the following: recurrent cough, especially nocturnal, recurrent wheeze, recurrent difficulty in breathing with a response to a bronchodilator, and spirometric features of airway obstruction. Statistical Analysis: The data were analyzed with SPSS version 16 using percentages, mean values, standard deviation, Chi-square test, Student's t-test, and multiple logistic regression. P value was significant at ≤0.05. Results: Asthma prevalence was 12.5%. The disease prevalence was comparable across ethnic groups and socioeconomic classes. Neither weight nor height differed significantly between the asthmatic and nonasthmatic pupils. Family history of asthma and physical stigmata of cutaneous atopy were significantly associated with the disease. Conclusions: The prevalence of bronchial asthma among the pupils studied suggests a current local disease burden that is comparable to those of communities in the industrialized countries. There is a need for improved health education and campaigns about the disease not only for Nigerians but also for other countries with the high prevalence.

Keywords: Childhood asthma, epidemiology, prevalence, spirometry

How to cite this article:
Akhiwu HO, Asani MO, Johnson AB, Ibrahim M. Epidemiology of pediatric asthma in a Nigerian population. J Health Res Rev 2017;4:130-6

How to cite this URL:
Akhiwu HO, Asani MO, Johnson AB, Ibrahim M. Epidemiology of pediatric asthma in a Nigerian population. J Health Res Rev [serial online] 2017 [cited 2018 Mar 18];4:130-6. Available from: http://www.jhrr.org/text.asp?2017/4/3/130/216061

  Introduction Top

Asthma may be defined as a chronic inflammatory disease of the airways associated with widespread but variable outflow obstruction of the airways, manifesting clinically with wheezing, recurrent cough, difficulty with breathing, and chest tightness.[1] While the airway obstruction associated with acute exacerbation may reverse either spontaneously or with medications, chronic inflammation remains the universal basis of the airway hyperresponsiveness to a variety of stimuli.[1],[2]

The cause of childhood asthma is yet to be determined, however, a combination of environmental exposure and inherent biological/genetic susceptibilities have been implicated.[3] The implicated trigger factors of asthma include house dust mites, molds and animal dander's, viral infections of the respiratory tract, domestic kitchen pollutants, and tobacco smoke. Exposure to household sprays, paint fumes, wood dust, stress, obesity, exercise, chronic sinusitis, as well as the use of medications such as the nonsteroidal anti-inflammatory agents.[4],[5],[6],[7] Although the cause of asthma is unknown, some past studies [8],[9],[10] have identified certain risk factors as being associated with a higher incidence of asthma and these includes family history of asthma, personal history of atopy, history of parents as smokers, and urban dwellers.

With an estimated 300 million disease sufferers of all ages, bronchial asthma remains a common cause of chronic ambulatory respiratory morbidity in the West African subregion.[11] In addition, the disease imposes a heavy burden on individuals, families, and indeed the entire society with increase in the cost implications of managing the disease on the economy of nations.[11] In the pediatric age group, a significant morbidity import includes the contribution of the disease to the number of missed school days and emergency room visits.[12] With the highest incidence of asthma being observed in children in the 6–11 years age range.[13]

In Zaria, four decades ago, asthma was described as being rare in childhood,[14] whereas 26 years later, Abubakar found the prevalence of 4.1% in the same area.[15] However, there is a paucity of recent data on the disease prevalence beyond the Southwest and Southeastern geopolitical zones of Nigeria. It is against this background that the present study was conceived and carried out to determine the epidemiology of asthma among primary school pupils in Kano metropolis.

As a school-based, cross-sectional study, it is envisaged that the majority of the participants who would not have otherwise presented to the health facility would be captured in the survey. This study is also expected to provide a database of the epidemiology of children with asthma in the local population.

  Materials and Methods Top

Kano metropolis, where the study was carried out, has an estimated population of 3.5 million [16] and four seasons: the hot and dry season, the warm and wet season, the warm and dry season, and then the cool and dry season (also called the harmattan season). The harmattan season spans December to February and sometimes can extend between November and March.[17]

There are eight local government areas (LGAs) in the metropolis: Dala, Fagge, Gwale, Kano Municipal, Tarauni, Nasarawa, Kumbotso, and Ungogo LGAs. Kano metropolis has 1914 primary schools registered by the state ministry of education.[18]

The present study is a descriptive, cross-sectional survey of the epidemiology of asthma among primary school children aged 6–11 years. The sample size was determined using the published table by Krejcie and Morgan.[19] For the purpose of this study, a margin of error of 3.5% and a confidence interval of 95% was used. The population of 6–11 years old in the selected primary schools was 18,546, therefore, the next higher value on the table was 25,000. The corresponding required sample size was 760 pupils. Adding 10% for nonresponse, this study aimed at recruiting 836 pupils.

The study periods were October 8, 2012–March 29, 2013 and November 14, 2013–December 23, 2013.

Ethical approval (ethical clearance number - NHREC/21/08/2008A/AKTH/EC/781) was obtained from the hospital ethics committee and the state ministry of education. While written consent was obtained from individual parents and assent from children older than 7 years.

Registered Nigerian primary school pupils aged 6–11 years as at last birthday, individual parental consent and assent from child were the inclusion criteria, whereas children with symptoms or diagnosis of cardiorespiratory morbidities such as pulmonary tuberculosis, chronic suppurative lung diseases, or congenital heart disease. Children who were unable to perform the required spirometric tests despite age eligibility and parents and children who refused to give consent were excluded.

There are eight LGAs in Kano metropolis, 30% of which making three LGA was considered representative.[20]

Fagge LGA has 154 schools of which 83 are private schools and 71 public. Five percent of the schools was estimated as eight schools, and hence the proportion of public-to-private schools selected was 4:4. Tarauni LGA has a total of 304 schools, of which 148 are public and 156 are private schools. Five percent of the schools was selected, that is, 15 schools and the proportion of public-to-private schools selected were 7:8. Nasarawa LGA has a total of 317 schools, of which 169 are public and 148 are private 5% of the schools selected was 16 schools and the proportion of public to private schools selected was 8:8.

Using the list of schools obtained from the ministry of education, a systematic sampling method was then applied. A number was randomly selected and tagged “n” and then every n th element was selected until the desired number of schools was selected; the same method was followed for the three LGAs.

Based on the population of each LGA vis-à -vis the target sample size and using the proportionate to size sampling method, the proportion of the sample size to be recruited from Fagge LGA was estimated as 127 pupils, whereas the corresponding figures were 518 and 191 pupils for Nasarawa and Tarauni LGAs, respectively. Making a total sample size of 836 pupils.

The number of eligible pupils from the school register was noted and a starting point was randomly selected. This number was tagged “n” and every nth pupil was chosen until the desired sample size for the individual school was obtained.

The children were identified and consent forms, patient information sheets, and questionnaires were administered. Each participant was given a period of 1 week to return his/her questionnaire. Each pupil was classified into a social class based on the criteria and computation of Oyedeji as documented in Braimah et al.[21]

Each participant was informed a day to the test day to have their breakfast by 6 a.m. The schools were also informed that the pupils recruited for the study were not to participate in any form of vigorous activity on the morning of the test.

On the morning of the test, the pupils were gathered in a bright room with no wind interference and asked if any of them had common cold or had taken a bronchodilator in the morning of the test. Any child who had common cold or had taken a bronchodilator in the morning of the test was excluded from the study for that day. The pupils were rested for at least 30 min before the tests.

For each of the participants, the standing height was measured in centimeters to the nearest 0.1 cm. Similarly, the body weights were measured in kilogram to the nearest 0.1 kg with the pupil's school uniform on, but without shoes using the same combined scale.

Each pupil was examined by the investigator for the presence of, as well as other concomitant cutaneous features of atopy, respiratory system/chest findings such as the presence of rhonchi, wheezing, chest wall deformity, and respiratory distress. The spirometer had a daily calibration check with the 3 L calibration syringe and also after every 8th pupil had been tested or after relocating from one school to another. The procedure for the required pulmonary function tests was demonstrated to each child by the investigator, assisted by the pulmonary function technician. The spirometric test was performed with the patient in the sitting position, with no neck tie, and their belts loosened using the designated spirometer. The mouthpiece of the spirometer was positioned in the child's mouth, and the child was required to perform the required vital capacity maneuver by blowing maximally through the mouthpiece (with evident manual occlusion of the nares) preceded by a deep inspiration. Each child performed the procedure thrice and the best of the three measurements (of the relevant lung function parameters) was recorded as the child's pulmonary function value.

The results of the spirometry readings were compared with standardized predicted values for age, height, and sex. Each of a reduction to <80% of the predicted forced expiratory volume in 1 s (FEV1), a similar magnitude of forced vital capacity (FVC) reduction, or a calculated ratio of FEV1/FVC of <0.70 were each considered indicative of an obstructive airway disease with bronchial asthma as the prime consideration.

The diagnosis of asthma was based on two or more of the following parameters in accordance with the Global Initiative for Asthma pediatric guidelines:[22]

  1. Recurrent cough, especially nocturnal
  2. Recurrent wheeze
  3. Recurrent difficulty in breathing with a prompt response to a bronchodilator or
  4. Spirometric features of airway obstruction.

The pupils diagnosed to have asthma were referred to a contact person at the teaching hospital for subsequent follow-up.

Statistical analyses were performed using the Statistical Package for the Social Science (SPSS version 16; SPSS Inc., Chicago, IL, USA). Qualitative data were represented as percentages, whereas quantitative data were recorded as mean values and standard deviation (SD). Chi-square test was used to determine associations between the categorical variables; Student's t-test was used to compare the means and SDs of the quantitative variables. For each of the associations explored, a P≤ 0.05 was considered significant. Multiple regression analysis was used to determine various clinical and historical parameters that were significantly associated with asthma.

  Results Top

While the study aimed at recruiting 836 pupils aged 6–11 years, 811 of the projected number were able to complete the study. This represented a response rate of 97%. Of the 25 pupils that did not complete the study, 15 (60%) of them was due to a respiratory tract infection, 8 (32%) of them opted out of the study, and 2 (8%) had a febrile illness with vomiting.

A total of 101 pupils were diagnosed with asthma, thus giving a disease prevalence of 12.5% of the study population.

A sizable proportion of asthmatic pupils were aged 8 and 9 years with a prevalence of 19.8% and 21.8%, respectively; 7-year-old constituted the least vulnerable age with the lowest age specific prevalence of 11.9% [Figure 1] and [Table 1].
Figure 1: Age-specific prevalence of asthma

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Table 1: Sociodemographic characteristics of pupils with asthma

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The mean height for the asthmatic pupils was 129 ± 10.2 cm, whereas the corresponding value for the nonasthmatic pupils was 128 ± 9.6 cm. The mean weight of the asthmatics was 26.4 ± 7.7 kg and the corresponding weight among the nonasthmatics was 25.5 ± 7.1 kg.

There was however no statistically significant difference in the mean weight and height of the asthmatic and nonasthmatic categories of pupils with a P= 0.56 and 0.23, respectively.

  Discussion Top

A prevalence of asthma of 12.5% among 6–11 years old in Kano metropolis is comparably higher than the corresponding prevalence data of 3% and 2.4% from the earlier reports from Enugu and Ibadan, respectively.[23],[24] Seasonal/geographic factors such as the longer, dusty harmattan months in the North, as well as climatic changes associated with indiscriminate tree felling, desert encroachment, and decrease in annual rainfall over the years may account for the regional disparity in the disease burden.[17],[25] The disease burden of the present study is however comparable to those recorded in some developed countries.[26]

The present study had marginal male gender preponderance in asthmatic pupils. This finding is in accord with the observations in some earlier reports.[27] On the other hand, a Tanzanian study [28] had reported a higher prevalence in females, an observation attributed to the local environmental peculiarities. While the slightly higher prevalence in the male pupils of the present study may be ascribed to male-related narrower airways, increased airway tone, and higher IgE levels,[27] it is noteworthy that the current gender-related difference in disease prevalence did not reach a statistically significant level. An observation consistent with that of a comparable study from Southwestern region of the country.[29]

With regard to the comparable prevalence of the disease across the common local ethnic groups, the plausible inference is that environmental factors (“nurture”) play a more important role than genetic predisposition (“nature”) an assertion supported by earlier authors.[30] On the other hand, the hereditary nature of atopy and airway hyperresponsiveness remained an incontestable finding of others.[31],[32] The finding of comparable ethnic disease prevalence in the present study would suggest that both “nature” and “nurture” contribute to the evolution of the disease.

The present study documented the highest disease prevalence among the upper middle class though this finding was not statistically significant. A finding at variance with the observation of an earlier report by Owoeye,[29] who documented higher though not statistically significant prevalence in the lower social strata. This class-related disease preponderance could be due to the tendency for sedentary indoor living and higher exposure to house dust mites seen in the children of such affluent families.

With regards to anthropometry, the mean height and weight of the children with asthma were slightly higher than the corresponding values in pupils without asthma. The difference, however, was not statistically significant. This is similar to the observation of Owoeye.[29] On the other hand, Addo-Yobo et al.[33] documented a higher prevalence of asthma as well as a significant difference in the weight and height between children from affluent families and those from less affluent homes. The authors,[33] however, could not draw a conclusion on the possibility of a direct relationship between these observed differences in the weight and height of the children from affluent homes and asthma. The finding that the anthropometric values of pupils with asthma in the present study were higher than those of their nonasthmatic peers may simply reflect the better nutritional provisions of these children, whose parents are more likely to be in the upper/middle socioeconomic categories.

Cutaneous features of atopy, constituted the most common clinical parameter, identified in the pupils with asthma. Despite this high prevalence, there was however no statistically significant difference between the presence of cutaneous features of atopy and the number of wheezing episodes in the past 12 months [Table 2],[Table 3]. This is in accord with the contention of earlier authors that atopy is therefore not the only underlying precipitant of exacerbation.[34],[35]
Table 2: Other observed clinical parameters of pupils with asthma

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Table 3: Association between cutaneous features of atopy and the number of wheezing episodes in the previous 12 months

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With reference to the commonly identified risk factors for asthma [Table 4], <50% of the pupils had a family history of asthma or cutaneous features of atopy. However, when multiple linear regression analysis was applied [Table 5] to the risk factors for asthma as well as the common clinical parameters observed in these children (family history of asthma, cutaneous features of atopy, chest wall deformity, tachypnea, and rhonci) it was observed that these factors could be considered as predictors of asthma in 49.6% of cases (R2 = 0.496), hence when the coefficients were applied it was observed that family history of asthma and cutaneous features of atopy were statistically significant associations of asthma whereas chest wall deformity, rhonci, and tachypnea seen outside acute exacerbation's were not significantly associated with the disease. This lends credence to past studies [34],[35],[36] that concluded that atopy and family history of asthma were common associations of asthma. All the pupils studied were urban dwellers and none of the parents admitted to smoking, hence their associations with the disease could not be determined.
Table 4: Prevalence of risk factors for asthma in pupils that met the diagnostic criteria for asthma

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Table 5: Multiple linear regression analysis of clinical and historical parameters and asthma prevalence in children

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A multiple logistic regression analysis was carried out to determine if asthma was significantly associated with the following independent variables; family history of asthma, cutaneous features of atopy, chest wall deformity, tachypnea, and rhonci. These variable were found to be able to statistically significantly predict asthma with F (5804) = 158.48, P < 0.000. R2 = 0.496.

With this R2 signifying that 49.6% of the variance in asthma can be explained by these independent variables. The correlation coefficients were then determined and it is represented in [Table 5].

  Conclusions Top

The asthma prevalence of 12.5% among school children aged 6–11 years in Kano metropolis suggests that asthma is a significant health problem in Kano metropolis. There is no significant difference in the prevalence of the disease with respect to ethnicity and social class. The height and weight were not significantly different between the children with asthma and those without asthma, whereas cutaneous stigmata of atopy were common among asthmatic pupils. The implication of these findings is a high prevalence rate for asthma (a disease that threatens health and economies) that cuts across ethnic groups and social classes. Lending credence to the need for policies that promote early identification of the disease, including screening for asthma in the school health program. There is also a need for improved health education and campaigns on how to identify the common symptoms of bronchial asthma, the need to seek medical intervention early, and making asthma medications affordable for those that need them. These measures are likely to reduce asthma burden and societal cost not only for Nigeria but also for other countries with the high prevalence of asthma.

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Conflicts of interest

There are no conflicts of interest.

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  [Figure 1]

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


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