Abstract
Introduction
The Health Literacy Measure for Adolescents (HELMA) is a multidimensional tool used to measure health literacy in adolescents. Previous studies on adolescent health literacy were primarily hospital-based, and the instruments used did not encompass all domains of health literacy. This descriptive cross-sectional study aimed to validate the HELMA questionnaire in secondary schools located in a rural and an urban local government area (LGA) of Osun State, Nigeria.
Methods
The Health Literacy Measure for Adolescents (HELMA) tool was validated among 430 adolescents selected using a four-stage sampling technique from Junior and Senior Secondary Schools located in rural and urban local government areas (LGA) of Osun State, Nigeria. Psychometric properties of the tool were assessed using Cronbach’s alpha and inter-item correlation.
Results
The adolescents were 13.5 ± 2.4 years old, and 50.7% were female. The Health Literacy Measure for Adolescents showed moderate to good psychometric properties. CFA showed good fit indices for an eight-factor model. The Cronbach’s alpha coefficient ranged from 0.73 to 0.89 for the various constructs. The intra-rater consistency, assessed by the intra-class correlation coefficient, was 0.93 (0.65–0.89), indicating good test-retest reliability. This study provides support for the use of the HELMA as a valid and reliable instrument to measure health literacy in adolescents in Nigeria.
Conclusion
The Health Literacy Measure for Adolescents (HELMA) is a valid and reliable tool for measuring the health literacy of adolescents aged 10–19 and can evaluate different levels of functional, interactive, and critical health literacy.
Keywords: Health literacy, In-school adolescents, Questionnaire validation
Background
Health literacy (HL) refers to the cognitive and social skills that enable people to access, understand, and use health information to promote their health [1]. The health literacy model comprises three divisions: functional, communicative, and critical literacy. Functional health literacy refers to a person’s ability to read, write, and use basic health information. Interactive health literacy refers to a person’s ability to communicate effectively with healthcare professionals and utilize the information received to manage their health effectively. Critical health literacy is the modern intellectual capacity that, alongside relational abilities, can be used to critically examine facts.
Adolescence is a transitional period between childhood and adulthood, characterized by interdependence, during which adolescents strive to make decisions independently. It is, therefore, essential to provide adolescents with accurate and reliable health information, enabling them to adopt health-promoting behaviours [2] and take charge of their own health [3]. The increased access to the internet due to the COVID-19 pandemic has its advantages. However, it has also led to exposure to a vast amount of health information whose validity and accuracy remain unverified.
Most researchers agreed that health literacy is related to culture and location, so that different settings may require different assessment tools [4, 5]. Despite numerous studies on the development and assessment of instruments used to measure health literacy in clinical settings [6], few studies have addressed the health literacy of adolescents [7], particularly within schools [8]. This is primarily due to the lack of a comprehensive definition of health literacy and the absence of proper assessment tools [9]. As suggested by Nutbeam, a good questionnaire for measuring health literacy should assess a person’s ability to access information from various sources, understand health information, and apply it appropriately to achieve personal benefit [1]. Hence, the choice of HELMA as a tool to validate in this study, as it meets all the criteria described by Nutbeam.
Traditional instruments of health literacy include the Rapid Estimate of Adult Literacy in Medicine (REALM) [10] and the Test of Functional Health Literacy in Adults (TOFHLA) [11]. These instruments are designed for use in the clinic environment but have a narrow scope. Healthcare providers use these instruments to identify clients with problems in health-related word identification (REALM) and study comprehension (TOFHLA). The tools assist healthcare providers in designing health appointments to provide conversation and match information to the client’s reading and writing abilities. Hence, these health literacy instruments are helpful within the healthcare setting; however, they are narrow in scope when applied to clients outside of healthcare settings.
Building on the REALM and TOFHLA, other instruments, such as the Newest Vital Sign (NVS) [12], aim to capture a more relational aspect of health literacy by assessing the capacity to apply medical facts (e.g., diet-related information) and make medical-related judgments. However, the NVS was also designed as a discerning tool for medical workers and relied mainly on the patient’s numeracy skills. Although it may be a suitable instrument for estimating applied calculation abilities, it may not be appropriate for a broader scope of medical conditions due to content compatibility issues. It may not assess more comprehensive skills and proficiency in health literacy [13].
Furthermore, previous studies reported that many adolescent health literacy instruments were adapted from adult versions [14–16]. They may be inappropriate since adolescent health literacy is likely to have very different elements and changes as an individual matures [14–16]. Furthermore, adolescents’ health literacy differs from that of adults [17, 18], and the instrument used to measure this needs to be adapted to the specific needs of a particular population in various contexts.
Research has shown that materials written in plain English and at a lower grade level result in better understanding and improved knowledge [19]. Individuals from diverse cultures, however, may not comprehend easy-to-read materials if Western constructs of health and health care are assumed, hence the need to validate a foreign instrument that needs to be used locally.
Furthermore, several health literacy assessment instruments are available [11, 20–21]. Low scores on these assessments, however, may not pinpoint the nature of the health literacy problem. The low score could be due to low literacy, limited English proficiency, or lack of familiarity with foreign health terms and concepts. Therefore, this study aimed to validate the HELMA questionnaire for measuring health literacy among adolescents in Nigeria.
Methods
Study location
Osogbo is the capital of Osun State, Nigeria. Osogbo is located between Latitudes 7°42’20”N and 7°49’20” N and Longitudes 4°30’20”E and 4°38’20” E. It shares boundaries with Ede, Egbedore, Ikirun, Ilesa, and Iragbiji. In 2006, the population of Osogbo was 155,507. Based on this figure, the population of Osogbo was estimated to be 201,900 in 2022 at the official annual growth rate of 3.7% [22] The majority of residents belong to the Yoruba ethnic group. In the LGA, the Yoruba language is widely spoken, while Islam, traditionalism, and Christianity are all actively practiced. The Osun-Osogbo festival is one of the significant celebrations conducted in the LGA, and the Ataoja of Osogbo is its supreme traditional ruler. The Osogbo School of Art, the Osogbo Grand Mosque, and the Sacred Grove of the Osun River Goddess, a UNESCO World Heritage site, are notable monuments in Osogbo. As of 2021, Osun State had 489 public secondary schools and 934 private secondary schools.
Study design
The study is a descriptive cross-sectional design, which is an appropriate method for investigating the occurrence of particular conditions or traits within a population at a specific moment in time.
Study population
In-school adolescents in selected public and private schools.
Inclusion criteria
Adolescents aged 10–19 years.
Students in JSS2 (grade 8) to SSS3 (grade 12).
Exclusion criteria
We excluded adolescents aged 10 to 19 years who had not yet attended a school session. Adolescents < 18 years whose parents refused to give consent.
Adolescents who did not provide assent.
Sampling technique
The study locations and respondents were chosen using a multistage sampling procedure. In stage one, a senatorial district was randomly selected using a simple random sampling technique by balloting from the three senatorial districts in Osun State. Stage 2: The balloting system randomly chose two rural LGAs and one urban LGA. Due to more schools in urban than rural areas, the number of rural LGAs selected was twice that of urban areas. Stage 3: We categorised the secondary schools into public and private groups using a list from each of the three LGAs we chose. Then, using a computer-generated table of random numbers, we selected five public and five private secondary schools from each LGA.
Stage 4: An arm of the class was chosen using a simple random sample procedure from each stratum of classes JSSS 2 to SSS3 (corresponding to Grades 8 to 12), making five classes from each school. Based on the predefined number of participants allotted to the school, a proportionate sample was drawn from the chosen classes.
Validation of HELMA tool
Although the HELMA questionnaire has been widely used in Iran [6], it was developed and validated by Ghanbari et al. [6]. It contains 44 items with eight sections, namely access, reading, understanding, appraise, use, communication, self-efficacy and numeracy. Each domain is measured on five scales: never, rarely, sometimes, usually, and always. The manual scoring of HELMA is shown in Table 1 below.
Table 1.
Manual scoring for HELMA
| Number of items | The minimum possible raw score | The maximum possible raw score | |
|---|---|---|---|
| Access | 5 (item 5–9) | 5 | 25 |
| Reading | 5 (items 10–14) | 5 | 25 |
| Understanding | 10 (items 15–24) | 10 | 50 |
| Appraisal | 5 (items 25–29) | 5 | 25 |
| Use | 4 (items 30–33) | 4 | 20 |
| Communication | 7 (items 34–40) | 7 | 35 |
| Self-efficacy | 4 (items 1–4) | 4 | 20 |
| Numeracy | 1 (item 41) | 1 | 5 |
The Cronbach’s (alpha) coefficient for the entire scale was 0.93. There is no evidence to confirm its validity and reliability in our local context The current study validated the HELMA questionnaire among adolescents in Nigeria using face, content, and construct validity, as well as reliability. This phase was conducted in two stages. The first stage involved content validation by experts, and the second stage consisted of administering a questionnaire to students to assess its reliability and validity.
Content validation by experts
For Content Validation, fifteen experts were selected from the fifty names available on the mailing list for the South–West region obtained from the Association of Public Health Physicians in Nigeria. The selection criteria from the list include having a Master of Public Health (MPH) degree and expertise in adolescent health. The selected professionals comprised public health physicians, demographers and paediatricians.
An invitation was sent to the experts via their e-mail addresses, and thirteen professionals eventually responded to the e-mail. The questionnaire was then mailed to the experts who responded to the invitation.
Procedures for content validation by experts
The experts determined the content validity of the 44-item questionnaire, which has eight subdomains. The thirteen (13) experts reviewed the questionnaire to ensure it followed proper syntax, phrasing, element allocation, and scale. They determined the content validity ratio (CVR) by rating each item on a 3-point Likert scale (1 being essential, 2 being beneficial but not essential, and 3 being not essential). Then, based on the Lawshe table, items that scored at least 0.54 were retained in the scale using Lawshe’s Table [23]. The Lawshe table is designed to interpret the CVR of the items assessed using the number of items rated as essential and the number of experts that made the decision. When fewer than half of the experts say “essential” for an item, the CVR is negative; when half say “essential” and half do not, the CVR is zero. When all say “essential,” the CVR is computed to be 1.00; it is adjusted to 0.99 for ease of manipulation. When the number saying “essential” is more than half but less than all, the CVR is somewhere between zero and 0.99, as shown in the Lawshe Table [23].
During this stage, two components were combined. “When visiting a doctor or health care provider, I can give them all the personal information they need, and when visiting a doctor or health provider, I can tell them the names of the medications I have previously used; it became “I am now able to disclose all of my personal information and previously taken drugs when I see a health care practitioner. The two questions merged were in the communication sub-domain of the health literacy questionnaire. The experts suggested the merging of the two questions in the communication domain because one of the questions (I am able to tell them the names of all previous medicines used) had a CVR of less than 0.54, and it should be deleted. The expert felt that providing the names of previous medications is an essential aspect of personal information; therefore, it should be included in the question on personal health information.
Following the content validity ratio, the communication subdomain has seven questions instead of eight. In addition to the above process, the thirteen specialists were asked to rate each item for relevance, precision, and coherence on a 4-point Likert scale (1 = not relevant, 2 = somewhat relevant, 3 = fairly relevant, and 4 = highly relevant). This was to determine the Content Validity Index (CVI). Items with a CVI value of ≥ 0.79 following Waltz and Brussel were retained in the questionnaire [24]. Four items did not meet this criterion. The experts suggested that the wording of the four items be rephrased. These four items were rephrased as indicated by the experts and rescored. Finally, forty-three items had a CVI value ≥ 0.79. Following the content validity check, the penultimate version of the questionnaire (health literacy measure for adolescents) had 43 items and was ready for the next stage.
Reliability
Analyses of internal consistency and test-retest reliability were used to rate HELMA’s reliability. The Cronbach’s alpha coefficient was calculated for each dimension and the overall questionnaire to assess internal consistency. According to Litwin and Fink, an instrument has satisfactory reliability if its Cronbach’s alpha coefficient is 0.70 or above [25]. Test-retest reliability was assessed to gauge the instrument’s stability; Baumgartner et al. [26] consider an Intra-class Correlation Coefficient (ICC) value of 0.4 or greater acceptable when computing the Intra-class Correlation Coefficients (ICC) for the same set of adolescents who completed the HELMA twice over two weeks. Statistical analysis was conducted using IBM SPSS version 20.0.
Construct validity
The exploratory factor analysis with varimax rotation was employed to evaluate the construct validity. Factor analysis is a technique used to reduce a large number of variables into a smaller number of factors. It helps to validate and improve inconsistency by confirming the relationship between survey items and identifying the total number of dimensions represented on the survey. We conducted analyses with various numbers of components (seven and eight) to identify the necessary factors. A scree plot and Eigenvalues were used to count the possible underlying factors [26]. Factor loadings up to 0.40 were deemed suitable for inclusion in the questionnaire. The test for sampling adequacy assesses whether the sample is suitable for factor analysis. For correlating data, the Kaiser-Meyer-Olkin (KMO) measure and Bartlett’s Test of Sphericity were utilized [27, 28].
Statistical validation of HELMA
The Cronbach’s Alpha reliability statistic was used to determine the internal consistency of the HELMA tool. Two of the original 43 items were eliminated from the final scale, leaving 41 items because the ‘Cronbach’s Alpha if-item-deleted’ was higher when they were omitted. The two items deleted were in the numeracy aspect of the questionnaire. These deletions reduced the number of items in the numeracy domain of the HELMA questionnaire to one instead of the initial three:
“Calculate the Body Mass Index of a person who is 156 cm tall and weighs 70 kg, using the formula BMI = weight/height2?” (Cronbach’s Alpha increased from 0.642 to 0.987).
“Calculate the individual’s body adipose status (based on the given information in the leaflet)?” (Alpha increased from 0.692 to 0.943).
Data collection
Data collection took place between February and December 2022. Data was collected using a facilitated self-administered questionnaire. All administered questionnaires were collected and checked daily for errors and completeness, with any necessary corrections made.
Measures and outcomes
The primary outcome of interest in this research is the Health Literacy Measure among Adolescents.
Results
Socio-demographic characteristics of respondents
Table 2 shows that 229 respondents were within the 10–14 age range. The respondents were, on average, 13.5 ± 2.4 years old. Half of the respondents (50.7%) were female. Most respondents identified as Christians and Yoruba, comprising 410 (95.3%) and 363 (84.4%) individuals, respectively.
Table 2.
Socio-demographic characteristics of respondents
| Variables | Frequency (N = 430) | Percentages (%) |
|---|---|---|
| Age in years | ||
| Mean = 13.5 ± 2.4 years | ||
| 10-14years | 229 | 53.3 |
| 15-19years | 201 | 46.7 |
| Sex | ||
| Male | 212 | 49.3 |
| Female | 218 | 50.7 |
| School | ||
| Public | 215 | 50.0 |
| Private | 215 | 50.0 |
| Ethnic group | ||
| Yoruba | 410 | 95.3 |
| Non-Yoruba | 20 | 4.7 |
| Religion | ||
| Christian | 363 | 84.4 |
| Muslim | 67 | 15.6 |
| Class | ||
| JSS2 | 139 | 32.3 |
| JSS3 | 59 | 13.7 |
| SSS1 | 56 | 13.0 |
| SSS2 | 66 | 15.3 |
| SSS3 | 110 | 25.7 |
Cronbach’s α co-efficient and ICC for the HELMA and its subscales
Table 3 shows that Cronbach’s alpha coefficient ranged from 0.73 to 0.89 for the various constructs. The overall scale Cronbach alpha value is 0.92. The intra-class correlation coefficient value is 0.93. It shows that HELMA has satisfactory stability.
Table 3.
Cronbach’s α co-efficient and ICC for the HELMA and its subscales
| Domain | Number of items | Cronbach’sα coefficient (n = 430) |
ICC (n = 43) |
|---|---|---|---|
| Self-efficacy | 4 | 0.74 | 0.75 |
| Access | 5 | 0.74 | 0.65 |
| Reading | 5 | 0.85 | 0.83 |
| Understanding | 10 | 0.82 | 0.86 |
| Appraisal | 5 | 0.89 | 0.77 |
| Use | 4 | 0.66 | 0.86 |
| Communication | 7 | 0.83 | 0.89 |
| Numeracy | 3 | 0.73 | 0.76 |
| Total Scale | 43 | 0.92 | 0.93 |
Factor loading and interpretation of 41 items of HELMA
The eight components or factors found by Principal Component Analysis (P.C.A.) with Varimax Rotation were responsible for 54.4% of the variance in a 41-item scale (Eigenvalue > 1). Each of these eight criteria included questions related to the different subscales of health literacy. The final 41-item scale provided sufficient evidence of validity based on its internal structure, as demonstrated by reliability testing through examination of internal consistency and component analysis (Tables 4, 5 and 6).
Table 4.
Factor loading and interpretation of self-efficacy, access, and reading domains of HELMA
| Domain description/scale element | Element loading | Engen value of the element | Percentage variance before rotation | Percentage variance after rotation |
|---|---|---|---|---|
| Self-efficacy (factor 1) | ||||
| Get more information about health | 0.792 | |||
| Find more messages on health | 0.767 | 8.332 | 16.933 | 18.937 |
| I can get needed information when I have health problems | 0.760 | |||
| I ask others about health messages I require | 0.756 | |||
| Access (factor2) | ||||
| Get access to messages on diet that are healthy and appropriate for my age | 0.759 | 6.130 | 12.234 | 13.932 |
| I have access to messages on exercise | 0.723 | 5.485 | 10.678 | 12.465 |
| I can get messages correct and needed care for my hair and skin | 0.678 | |||
| I can get information on mental health correct for my age. | 0.829 | |||
| I can get needed information on health messages on the web | 0.783 | |||
| Reading (factor 3) | 0.757 | |||
| Can read pamphlets on prescription | 0.684 | |||
| Read booklets on food issues | 0.792 | |||
| Read booklets on disease control | 0.673 | |||
| Read messages on medicine in newspapers and magazine | 0.757 | |||
| Read medical messages on the web |
Table 5.
Factor loading and interpretation of appraisal and use domains of HELMA
| Domain description/scale element | Element loading | Engen value of the element | Percentage variance before rotation | Percentage variance after rotation |
|---|---|---|---|---|
| Appraisal (factor 5) | ||||
| Can judge the accuracy of new health information. | 0.722 | |||
| Can correlate messages gotten from various origins? | 0.752 | 3.348 | 7.776 | 7.609 |
| Identify correct messages from contradictory messages. | 0.731 | |||
| Can correctly decide which materials to believe. | 0.862 | |||
| Can make informed choices based on dietary messages. | 0.778 | |||
| Use (factor 6) | ||||
| When purchasing food, I make my choice based on the information provided in the attached leaflet. | 0.740 | 2.131 | 5.344 | 4.842 |
| When choosing food, I pick one without preservatives. | 0.757 | |||
| I utilize my knowledge of health on a daily basis. | 0.779 | |||
| I try to maintain a normal weight. | 0.722 |
Table 6.
Factor loading and interpretation of communication and numeracy domains of HELMA
| Domain description/scale element | Element loading | Engen value of the element | Percentage variance before rotation | Percentage variance after rotation |
|---|---|---|---|---|
| Communication (factor 7) | 0.745 | |||
| Can effectively communicate my health-related concerns. | 0.787 | 1.584 | 4.342 | 3.600 |
| Problems with health care workers. | 0.785 | |||
| I can provide individual details and medical information to healthcare workers when I am in the hospital. | 0.861 | |||
| I can ask questions on issues bordering me when visiting the health practitioner. | 0.884 | |||
| I can share health messages I obtain with others. | 0.976 | |||
| Suppose I have queries with health issues. I can get messages and counsel from others. | 0.755 | |||
| I can ask questions about my previous findings on health from the medical practitioner. | ||||
| I discuss with my pair not to practice risky behavior. | ||||
| Numeracy (factor 8) | ||||
| Calculate how many carbohydrates you can receive from this food label. | 0.569 | 1.360 | 4.234 | 3.091 |
Table 7 shows the Kaiser-Meyer-Olkin Measure of Sampling Adequacy for the sampling frame used in this study was 0.880, approximately 0.9 indicates that the sampling frame for this study is adequate and it is very significant at 5% level of significance.
Table 7.
KMO and bartlett’s test
| Kaiser-Meyer-Olkin Measure of Sampling Adequacy. | 0.880 | |
|---|---|---|
| Bartlett’s Test of Sphericity | Approx. Chi-Square | 5310.273 |
| df | 946 | |
| p-value | < 0.0001 | |
Figure 1 presents the screen plot of Eigen values iterated after component factor analysis was employed on the 41-item HELMA instrument. As displayed in the appendix, at the beginning of the plot, there is a rapid drop in eigenvalues. This corresponds to the first few factors of HELMA, which explain most of the variance in the data. These factors are the most important in illustrating the underlying structure of the data represented by Eigenvalues > 1 which included 8 factors. The elbow point represents a natural break in the eigenvalues, suggesting that factors beyond this point may not be adding much more information to the model. The number of factors to retain has been chosen just before the elbow point (Eigenvalues ≤ 1).
Fig. 1.
Scree Plot of the exploratory factor analysis of HELMA
Discussion
This study attempted to validate a multidimensional tool for measuring health literacy among secondary school students in Osun State. After the validity and reliability phases were completed, the health literacy measure for adolescents (HELMA) consisted of 41 questions divided into eight domains: access, reading, understanding, appraisal, use, communication, self-efficacy, and numeracy. Most adolescents were able to complete the questionnaire within 25 min without difficulty. These findings suggest that HELMA would be an easy-to-use instrument for future studies.
The reliability of an instrument can be measured by its internal consistency, which indicates the extent to which the different dimensions of the instrument measure the same construct [29]. In the case of the 41-item HELMA, reliability analyses were conducted to determine if the eight different domains all measure the same construct of health literacy. The total score of HELMA displayed good internal consistency, with a Cronbach’s alpha of 0.79. The subscales also had values that can be considered satisfactory (access, reading, appraisal, and use) or good (communication, self-efficacy, understanding and numeracy). Overall, these values were comparable to what was obtained by the authors of the original HELMA questionnaire [6]. However, they had obtained an excellent Cronbach alpha of 0.93 for the total HELMA scale, whereas our data resulted in a Cronbach alpha of 0.79, which is considered good. Another study, which evaluated the psychometric properties of the HELMA instrument found a slightly lower Cronbach alpha of 0.74 for the overall HELMA scale among youths from Malaysia and Sri Lanka [30].
The best fitting model for our data, according to the CFA, was the eight-factor model, which excluded two questions from the numeracy scale, although the fit statistics for both models tested were good. The results of the factor correlations differed significantly from those of the other factors. This unusual finding can be attributed to the unique scoring system of the numeracy sub-scale, which uses a binary scoring system that is different from the ordinal Likert scales used for the other subscales. Binary data, with its limited variability and lack of nuance compared to ordinal data, can result in a loss of information. Furthermore, the assumption of equidistant intervals inherent in ordinal data does not apply to binary data [31]. Unusual factor loadings suggest that the scale may not be measuring the same underlying construct as other subscales. However, numeracy is one important aspect of health literacy [32] and thus complements the other dimensions. The reason for this finding might be that the students did not respond to the numeracy items in the same way they did to the other items. This could be due to difficulty in understanding mathematical information. The varied response might explain the unusual pattern in factor loadings and correlations observed. To ensure the numeracy items better align with the overall construct of health literacy as measured in this context, further evaluation or adjustment of the items may be necessary.
Although the validation of the HELMA provides new information about health literacy of adolescents in Nigeria, we acknowledge that the methodology used in our study has certain limitations. Convergent and discriminant validity were not done in this study because it is a pilot study. Future validation studies of the HELMA should consider examining convergent validity and discriminant validity.
Conclusion
The Health Literacy Measure for Adolescents (HELMA) is a valid and reliable instrument for measuring the health literacy of adolescents This supports its use in educational settings and provides a helpful first step for its application in other settings. Also, revision and possible modification of items within the numeracy scale may be necessary to better reflect the overall health literacy construct.
Acknowledgements
We wish to acknowledge all our research assistants and the study participants for their cooperation and hard work.
Authors’ contributions
All authors were involved in conceptualizing the research idea and topic, designing the methodology, and preparing the proposal. FOF carried out the study as part of his PhD work, and he is responsible for the overall content and serves as guarantor. OO, AO, AF, and OAO supervised and provided valuable suggestions and mentorship that helped shape the study into its present form. All the authors read and approved the final version of the manuscript.
Funding
This research was funded by the Consortium for Advanced Research Training in Africa (CARTA). The African Population and Health Research Center and the University of the Witwatersrand jointly lead CARTA. CARTA is funded by The Carnegie Corporation of New York [grant no. G-19-57145], The Sida [grant no. 54100113], and by the Uppsala Monitoring Centre and the DELTAS Africa Initiative [grant no. 107768/Z/15/Z]. The DELTAS Africa Initiative is an independent funding scheme of the African Academy of Sciences (AAS)’s Alliance for Accelerating Excellence in Science in Africa (AESA) and supported by the New Partnership for Africa’s Development Planning and Coordinating Agency (NEPAD Agency) with funding from the Wellcome Trust (UK) and the UK government. The statements made, and views expressed are solely the responsibility of the authors.
Data availability
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to ethical considerations. Data are available on reasonable request.
Declarations
Ethics approval and consent to participate
Ethical approval for this study was obtained from the Institute of Public Health (IPH) Ethics Review Committee, Obafemi Awolowo University, Ile-Ife, Nigeria (IPH/OAU/12/1951). This study was conducted in accordance with the ethical standards outlined in the Declaration of Helsinki and its subsequent amendments or comparable ethical standards. The Osun State Ministry of Education permitted the study to be conducted. The authorities of the chosen schools also gave their approval. Informed consent was obtained from parents and guardians of respondents less than 16 years old. Assent was also obtained from respondents less than 16 years old. Informed consent was obtained from respondents 16 years and above.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to ethical considerations. Data are available on reasonable request.