Prevalence and factors associated with hypertension among school children and adolescents in urban and semi‐urban areas in Cameroon

Abstract Few data to date exist on pediatric hypertension (PH) prevalence and risk factors in semi‐urban areas in Cameroon, and they are believed to be the same as urban areas. These data are needed to design targeted preventive strategies and contribute to reducing the burden of PH in Cameroon and countries with equivalent standards of care. The authors conducted a cross‐sectional study, from November, 2017 to June, 2018, in primary and secondary schools, from semi‐urban (Bamboutos, West Region) and urban (Mfoundi, Center Region) settings in Cameroon, including children and adolescent aged between 3 and 19 years, recruited on a stratified probability sampling. PH was defined according to the American Academy of Pediatrics 2017. Overall, 1001 and 842 participants were, respectively, included in urban and semi‐urban areas. The overall average age was 13.9 ± 4.03 years, and two‐thirds were girls. Overweight and obesity were more prevalent in urban area (overweight: 17.1%; obesity: 5.9%), compared to semi‐urban (overweight: 1.1% and obesity: 0.8%) (p < .001). The prevalence of hypertension was higher in urban (12%) than semi‐urban areas (8.6%) (p = .01). We have identified as factors associated with PH: age > 14 years (OR = 3.18 [1.6; 6.2]) and secondary level of education (OR = 2.5 [1.2; 5.5]) in urban areas; family history of hypertension (OR 1.93 [1.1; 3.4] in semi‐urban areas. PH prevalence is higher in urban than semi‐urban areas, and the associated factors are not the same. Policies to address hypertension in the pediatric population must be targeted and tailored to the different population profiles.


INTRODUCTION
There is a progressive increase in the prevalence of hypertension among children and adolescents living in sub-Saharan Africa (SSA). The currently available epidemiological data indicate prevalences ranging from 0.3 to 24.08%. [1] Several facts should alert public health policies in the fight against this scourge. Pediatric hypertension (PH) is unfortunately still underdiagnosed and remains for a long time unrecognized until the occurrence of complications. [2,3] The prevalence of major modifiable risk factors such as overweight and obesity is constantly increasing in children and adolescents living in Africa. [4] It calls us for regular and broader screening for hypertension in pediatric populations and rigorously addresses its potential risk factors. Therefore, it is important to routinely update epidemiological data on PH in SSA to improve the public health strategies implemented at the local, regional, and national levels.
Policies to address hypertension in the pediatric population must be targeted and tailored to the different population profiles identified beforehand. [5] It has been shown that environmental factors influence the prevalence of obesity and overweight, which are major risk factors for PH. [4] Indeed, obesity-promoting factors like sedentary lifestyle and obesogenic diet are related to the standard of living and the area of residence, whether it is urban, rural, or semi-urban in Cameroon. [6,7] Although their significance in shaping preventives strategies, few data to date exist on PH's prevalence and risk factors in semi-urban areas in Cameroon and are believed to be the same as urban areas. The present study was conducted in Cameroon, a microcosm in SSA and will provide more information on this topic to improve preventive medicine strategies to reduce the burden of PH in Cameroon and countries with equivalent standards of care.

Study design and settings
We conducted a cross-sectional study, during 8-month from November schools (primary and secondary). [9] The semi-urban setting was the Bamboutos department, with the city of Mbouda as its capital. It is located in the West region of

Participants
We have included all children and adolescent, aged between 3 and 19 years old (Adolescents between 10 and 19 years old) attending public and private elementary schools, high schools, and colleges located in the study sites, having consented to participate in the study and whose parents or legal guardians have given their written and informed assent. Participants who were registered but absent on the day of data collection were excluded, as were all participants already known to be hypertensive or taking antihypertensive medication.

Sample size estimation
The minimum sample size was estimated at 827 participants for each group, using the formula for comparison of proportions between two groups contained in the article by Bouyer and Colleagues. [10] For this purpose, we defined the statistical risk at 5%, the power at 80%. We used the urban prevalence (2.2%) of hypertension in primary and secondary schools in the city of Yaoundé obtained in 2014 by Donmani. [11] In the absence of a study, we used an estimated value of 1% for rural prevalence.

Sampling
We used stratified probability sampling with two levels of stratification.

Second level: selection of classrooms
We formed three strata within the nursery, primary, and secondary schools in each setting. All schools were classified according to the Using Research Randomizer version 4.0, we systematically drew one classroom for each stratum and each school selected above. We had administrative authorization, making a total of 138 primary and secondary classes.

Data collection
After BMI was normal between the 5th and < 85th percentile, and underweight < 5th percentile. [12] Excess weight includes obese and/or overweight patients.

Blood pressure measurement and hypertension definition
Blood pressure was measured with an OMRON ® electronic BP monitor with an adapted cuff after a 15-min rest period. We performed three measurements spaced 10 min apart, and BP was defined as the average of the last two measurements. Hypertension was defined in children and adolescents based on the recommendations of the American Academy of Pediatrics 2017 [13] : normal BP: BP < 90th percentile for age, sex, and height (< 13 years); or < 120/< 80 mm Hg (for adolescents ≥13 years); high BP: BP ≥ 90th percentile and < 95th percentile for age, sex, and height (< 13 years); or 120-129 systolic and diastolic < 80 mm Hg for adolescents ≥13 years; hypertension: ≥95th percentile for age, sex, and height (< 13 years); or ≥ 130/80 mm Hg in adolescents ≥13 years; grade I hypertension: BP ≥95th percentile and < 95th percentile + 12 mm Hg for age, sex, and height (< 13 years); or 130-139 systolic and/or 80-89 mm Hg diastolic in adolescents ≥ 13 years; grade II hypertension: BP ≥95th percentile + 12 mm Hg for age, sex, and height (< 13 years); or > 140/90 mm Hg for adolescents ≥13 years. Systolic and diastolic hypertension were defined for the previously specified age-specific systole and diastole values, respectively.
Pre-hypertension has been defined according to the fourth report on the diagnosis, evaluation, and treatment of high BP in children and adolescents. We consider a BP above the 90th and less than the 95th percentile for age, height, and weight before 12 years, and ≥120/80 but < 95th percentile after 12 years old. [14] Hypertension and prehypertension in patients 18 and 19 years of age were defined according to the Eighth Joint National Committee (JNC8). [15] Participants who were diagnosed with a PH were referred for appropriate management.

2.6
Statistical analysis Data

RESULTS
Two thousand five hundred students were identified, but 1843 were finally included, comprising 1001 in urban areas and 842 in semi-urban areas. Six hundred fifty-seven students could not be recruited because they did not consent to participate in the study or were absent on the day of data collection. Students from public schools were more represented (urban area (524; 54.8%), semi-urban area (358; 57.8%)), as well as secondary school students (urban area (816; 81.5%), semi-urban area (736; 87.4%)).

Characteristics of the sample
The overall average age was 13.9 (4.03) years, and the most repre-

Prevalence of pediatric hypertension in urban and semi-urban settings
The prevalence of hypertension in the whole sample was 10.4%. It was higher in urban areas (120; 12%) compared with semi-urban

Factors associated with pediatric hypertension in urban and semi-urban settings
In the urban setting, the factors associated with hypertension were: There was no association with excess weight (obesity and overweight) in both areas ( Table 3).

DISCUSSION
Data on PH in Cameroon and SSA are needed and must be updated to guide public health strategies. It is also important to determine the epidemiological profile of target populations to conduct efficient interventions. In Cameroon, few studies have addressed hypertension in children and adolescents by focusing on geographic origin. In the present study, we found a higher prevalence in urban areas (12%) than semiurban areas (8.6%), and the associated factors were not the same in the two regions. Ezeudu and Colleagues also in Nigeria (6.3%) [16][17][18][19][20] . These prevalences were synthesized by Noubiap and Colleagues in a systematic review in SSA, revealing an overall prevalence of 5.5%, and Song and Colleagues who found a prevalence of 4% in a global systematic review. [21,22] In Cameroon, few population data are available, the most recent being Chelo and Colleagues survey (1.6%), which found a lower prevalence than ours. Still, they have worked on a population of 5-17 years old, with younger average age (9 ± 5 years), all in elementary school. [23] Hypertension in children and adolescents is, therefore, a public health problem that should be detected and treated well before it occurs, particularly in patients with prehypertension who also represent a significant proportion, 10% in our study, 2.5% in the survey by Okpokowuruk and Colleagues in a semi-urban environment, 8% in the survey by Amponsem-Boateng and Colleagues, and 26.7% in the study by Bhimma and Colleagues. [16,18,24] In urban and semi-urban areas, the characteristics of the populations are not always the same, starting with diet and physical activity, which are known to be significant determinants of hypertension and are strongly influenced by geographical origin. Indeed, we found that the prevalence in urban areas was significantly higher than in semi-urban areas. In the African literature, some authors have studied the patients, notably Obika and Colleagues, who found no difference in the prevalence of hypertension in urban, rural, and semiurban areas in Nigeria. [25] Agyemang and Colleagues found lower BP figures in rural areas, with no difference between semi-urban and rural areas. [26] Furthermore, we found a high prevalence of systolic and diastolic hypertension in urban areas compared to semi-urban areas. This contrasts with the Ejike and Colleagues study results, which observed an increase in systolic BP in urban areas compared to nonurban areas and an increase in diastolic BP in non-urban areas compared to urban areas. [27] However, the profile of our populations was not the same; they worked on a population of adolescents only.
This disparity in prevalence relates to the epidemiological gap of the population and calls for a targeted strategy, as pointed out by Noubiap and Colleagues. [5] Several factors may influence the occurrence of hypertension in children and adolescents. We found that these factors differed in urban and semi-urban settings. Indeed, only age and high school education significantly increased the risk of hypertension in urban areas. In semiurban areas, only a family history of hypertension was an associated factor. Age, being a known risk factor for PH, reflects the accumulation and progression of different risk factors and is dependent on education level. [22,23]  Nigeria. [16,17,23,24,28] The absence of these risk factors in our population suggests that other associated factors could play a role. Notably, the diet that is principally rich in fruit and vegetables and low in salt has not been evaluated, regular physical activity, birth weight, and birth term, for which data could not be collected.
In the light of these results, it seems crucial to understand that the epidemiological profile of children and adolescents with hypertension is not totally the same in urban and semi-urban settings. The implications of these results could be at several levels, in particular primary prevention strategies that need to be adjusted at the community, regional, and national levels; the need to regularly update data; and the need to evaluate long-term follow-up to control potential risk factors and address them appropriately. The interpretation of the results of our study must nevertheless take into account several limitations: the possibility of a white coat effect and/or masked hypertension, which were not evaluated during our research and whose impact on prevalence is not negligible, especially in SSA [29] ; the different references defining hypertension in children and adolescents, which limits the comparison with certain studies; and the analysis of specific risk factors for hypertension, notably diet, which unfortunately are not yet well codified in our context.

CONCLUSIONS
PH prevalence is higher in urban than semi-urban areas in Cameroon, and the associated factors are not the same. Policies to address hypertension in the pediatric population must be targeted and tailored to the different population profiles. However, it is necessary to obtain longterm follow-up data to better define the risk factors for PH in our context, both in urban and semi-urban areas.