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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 20  |  Issue : 4  |  Page : 143-148

Cardiovascular disease risk profile in Nigerian school children


1 Department of Paediatrics, University of Jos, Jos University Teaching Hospital, Jos, Nigeria
2 Department of Pediatrics/Hematology, Emory University, Atlanta, Georgia, USA
3 Department of Human Physiology, University of Jos, Jos, Nigeria
4 Department of Chemical Pathology, University of Jos, Jos University Teaching Hospital, Jos, Nigeria

Date of Web Publication17-Apr-2018

Correspondence Address:
Dr. Christopher Sabo Yilgwan
Department of Paediatrics, University of Jos, PMB 2076, Jos
Nigeria
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DOI: 10.4103/1118-8561.230260

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  Abstract 


Background: Cardiovascular disease (CVD) is a major cause of death among adults worldwide. It is acknowledged that its risk factors have their roots in childhood. The present study evaluated CVD risk factors in primary school children in a Nigerian peri-urban setting. Methodology: This cross-sectional study was carried out in two primary schools in Jos South local government area, Plateau State, Nigeria. The 241 children studied were chosen using a systematic random sampling technique to select the children from each school. Pretested questionnaire was used to elicit the information on family characteristics and individual characteristics while standard anthropometric and laboratory procedures were used in evaluating the CVD risk factors. Results: Overall, 137 (56.8%) were females (M:F = 0.76), 151 (62.7%) were from the middle class, 59 (24.5%) from lower class while 31 (12.9%) were from the upper class. The overall prevalence of at least one cardiovascular risk factor was 54%. Sedentary lifestyle was the most common CVD risk factor in 32.4% of subjects followed by obesity (13.7%), adverse CVD event in family (11.6%), high low-density cholesterol (10.3%), high total cholesterol (TC) (9.1%), and hypertension (9.1% combine, 7.1% diastolic, and 5.8% systolic). Linear regression analysis showed that body mass index (BMI) for age (β = 0.41, P < 0.001), systolic blood pressure (BP) (β = 0.94, P = 0.03), diastolic BP (β =1.26, P = 0.01), and TC (β = 0.07, P = 0.04) significantly rise with age. BMI for age (P = 0.02) was significantly higher in female subjects compared with their male counterparts. Conclusions: From the findings of the present study, interventions related to modifiable risk factors, such as encouragement of physical exercise and sports in schools, healthy and prudent diet, and weight control programs should be undertaken early in life so as to help control the development of and the epidemic of CVD in later life.

Keywords: Cardiovascular risk, children, Nigeria, school age


How to cite this article:
Yilgwan CS, Hyacinth HI, Ige OO, Abok II, Yilgwan G, John C, Isichei CO, Okolo SN, Bode-Thomas F. Cardiovascular disease risk profile in Nigerian school children. Sahel Med J 2017;20:143-8

How to cite this URL:
Yilgwan CS, Hyacinth HI, Ige OO, Abok II, Yilgwan G, John C, Isichei CO, Okolo SN, Bode-Thomas F. Cardiovascular disease risk profile in Nigerian school children. Sahel Med J [serial online] 2017 [cited 2018 Aug 19];20:143-8. Available from: http://www.smjonline.org/text.asp?2017/20/4/143/230260




  Introduction Top


Cardiovascular diseases (CVDs) have emerged as important causes of morbidity and mortality in low- and middle-income countries.[1],[2],[3],[4],[5] Although infectious diseases and undernutrition had hitherto been the main causes of morbidity and mortality in Sub-Saharan Africa rapid urbanization in recent decades, coupled with the far-reaching effects of globalization, have resulted in an increase in the prevalence of noncommunicable diseases (NCDs) including CVD.[1],[2],[3],[4],[5]

NCDs are predicted to increase alarmingly in Africa, and the developing countries in the next few years if urgent measures are not taken to reverse the trend.[3],[4],[5] The trend is largely attributable to the new working and leisure standards that most of the population in the low- and medium-income countries, including Nigeria, have adopted and the significant changes in the quality, content, and quantity of food consumed, especially with the proliferation of fast food outlets and the attendant risk they post to healthy nutrition.[3],[4],[5] Considering that biological changes take place more rapidly during childhood and adolescence than in any other period of life, it is reasonable to view this age group as an important category for investigating CVD risk factors.[6],[7],[8] Further, evidence shows that risk at this age tends to either carry on to adult life and/or is a significant predictor of future cardiovascular event(s).[6] Studies have demonstrated that CVD have their roots in early childhood with significant influence of environmental factors especially those related to dietary habits and physical activity both important precursors of hypertension and obesity.[6],[7],[8]

Despite the public health significance of CVDs globally, few published reports exist of the concentrations of specific risk factors for CVD in children in Nigeria.[9],[10],[11],[12] The present study examined the profile of CVD risk factors in primary school children of Jos South local government area (LGA), Plateau State, Nigeria.


  Methodology Top


Subjects

This was a cross-sectional survey, with laboratory and physical examination components, carried out among school children aged 6–12 years in Hwolshe Community, a suburban area in Jos South LGA of Plateau State in Nigeria. The sample size was determined based on the 22.3% prevalence of cardiovascular risk in a previous study done among secondary school students in Jos, Nigeria.[13] Two schools were randomly selected from the list of six schools within Hwolshe electoral ward and their school registers used as the sampling frames in the selection of study subjects. A systematic sampling strategy was used with proportionate allocation to ensure that each primary school class or grade (from one to six) was adequately represented. A self-administered questionnaire was used to obtain basic information on personal and family medical and social history from consenting parents or guardians. Socioeconomic class (SEC) was determined using the criteria developed by Olusanya et al. based on a grading system that incorporates paternal occupation and maternal highest educational attainment.[14]

Ethical clearance was obtained from the research and Ethics Committee of the Jos University Teaching Hospital while informed consent and assent were obtained from the parents/guardian and the children, respectively.

Anthropometric measurements

The heights of subjects were measured to the nearest one-tenth of a centimeter using the Healthline ® stadiometer, according to standard protocols.[15] Body weight was measured to the nearest one-twentieth of a kilogram using the Healthline ® standing scale which has an accuracy of 50 g, also following standard measurement protocols.[15]

Waist circumference was measured to the nearest 0.1 cm at the midpoint between the lower costal border and the top of the iliac crest with the measurement taken at the end of a normal expiration using an inextensible measurement tape.[15] Hip circumference was measured at the horizontal level of maximum circumference around the buttocks using an inextensible measurement tape.[15] Waist-height ratio was calculated as child's waist circumference in centimeters divided by the height in centimeters. Waist-hip ratio was calculated as the child's waist circumference in centimeters divided by the hip circumference in centimeters.[15] Standard growth charts including the WHO growth chart was used for the interpretation of all anthropometric data so obtained.[16],[17],[18]

Cardiovascular risk factors measurement

Body mass indices were calculated from the heights and weights of the children, which were carefully measured according to standard protocols.[17],[18] Underweight was defined as body mass index (BMI) <5th percentile for age and sex, obesity as BMI ≥95th percentile, and overweight as BMI ≥85–95th percentile for age and sex, respectively.[18] Truncal obesity was defined as 95th percentile waist circumference for age and sex according to the Center for Disease Control standards.[17] Blood pressures (BPs) were measured using a standard mercury sphygmomanometer (Accosson ®, UK) following standard protocols on BP measurement.[19] Each child's BP was measured in the sitting position after resting for at least 15 min. Three readings were taken and the average value recorded. Those children with abnormal BP readings had a repeat assessment/measurement 6 weeks after the previous reading. The seventh report of the Joint National Committee 7 on BP criteria were used for determining normal and abnormal BP values for each child.[19]

An interviewer-administered questionnaire was used to collect information related to the child's weekly activity. Physical activity level was assessed using two criteria: (1) Average television (TV) watching time, and (2) duration of weekly sporting activities. Physical inactivity was defined as >3 h of television/video game watching/day and/or <30 min vigorous exercise/day.[20],[21],[22]

Following standard procedures, blood was collected from each child after an overnight fast of at least 8 h, and stored at −20°C for about 24–48 h until analyzed. For children who had already had breakfast, blood collection was delayed until the end of school to allow for the 8 h fast. Blood was centrifuged, the serum was drawn into nonheparinized cryovials and then stored at −20°C until analyzed for total cholesterol (TC), high-density lipoprotein-cholesterol (HDL-C), and triglycerides (TGs) concentration. Serum lipid profile (TG, TC, and HDL) was determined using commercial test kits (Roche Diagnostics Ltd., Sussex, UK) at the Jos University Teaching Hospital Chemical Pathology Laboratory.

Data analysis

Data were analyzed using SPSS version 18 IBM Corporation. Descriptive statistics of the baseline characteristics of study subjects was described using proportions, mean, standard deviation, frequency, and percentage. Chi-square test was applied for test of proportions between the different groups used while Student's t-test was used to compare the means of studied biochemical and physiological parameters. Linear regression analysis was also carried out to evaluate relationships between variables. P < 0.05 at 95% confidence interval was taken as significant in all analyses.


  Results Top


The mean values of sociodemographic, clinical, and laboratory parameters of the studied subjects are presented in [Table 1]. The male and female subjects were similar with regard to their mean ages, average TV watching time, BMI, systolic BP (SBP) and diastolic BP (DBP), social class, and serum lipid values. Only the waist and hip circumferences showed a significant difference between the sexes (P = 0.04).
Table 1: General (baseline) characteristics of studied subjects

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Prevalence of cardiovascular risk factors

Fifty-four percent (54%) of subjects had at least one CVD risk factor [Table 2]. Significantly, more female subjects had gross obesity (18.2%) and truncal obesity (5.8%). None of the other parameters showed any significant difference between the sexes [Table 2].
Table 2: Prevalence of cardiovascular disease risk factors in studied children

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After stratification by social class, significantly more children in the upper social class lived sedentary lifestyles compared with their counterparts from the middle and lower social classes (P = 0.004). Similar patterns were noted for systolic and diastolic hypertension with more children from the upper social class households being hypertensive [P < 0.001, [Table 3].
Table 3: Prevalence of cardiovascular disease risk factors according to social class

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Regression models of cardiovascular risk factors and sociodemographic factors

Linear regression analysis showed that BMI (P < 0.001), SBP (P = 0.03), DBP (P = 0.01), and TC (P = 0.04) were significantly associated with age while only BMI (P = 0.02) was significantly associated with female gender. In contrasting the CVD risk factors by social class, only physical activity tended to be significantly associated with higher social class (P = 0.03) [Table 4].
Table 4: Regression coefficients (β) and P value for linear models of cardiovascular risk factors according to sociodemographic factors

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  Discussion Top


The present study demonstrates a high prevalence of CVD risk factors in Nigerian children, with 54% of them having at least one CVD risk factor. This finding is consistent with reports from Canada (58%) and Portugal (54%) in studies carried out among school children by Reed et al.[22] and Ribeiro et al.,[23] respectively. It is, however, higher than the 35% reported from Tanzania by Chillo et al.[24] in 2009. Although the latter study as well as ours both relate to African school children with similar age range, there may be sociocultural variations that could explain the difference in the prevalence of cardiovascular risk factors.

Physical inactivity was the major risk factor observed in the present study, with 33% of the subjects engaging themselves almost exclusively in TV watching and playing video games during their leisure time - similar to the 39% reported in another African study.[24] We found children from the upper SEC to be significantly more sedentary compared with the other social classes, in tandem with reports from the USA [25] and Brazil [26] although hitherto not highlighted/investigated in an African study.

Obesity was the second most common CVD risk factor, we identified in 13.7% of the studied children. This is similar to reports on Sudanese (13.0%) and Brazilian (12.7%) school children using the same criteria.[26],[28] However, our finding is at variance with the 2% and 18% prevalence reported among rural and urban Nigerian school children. As has been frequently reported,[22],[23],[24],[25],[26] our study demonstrates obesity to be significantly more prevalent among girls compared to boys. Second, the higher prevalence of obesity that we found in the upper SECs is similar to reports from the previous studies among black children in the USA but differs from studies done among Caucasian children which tend to show the converse.[8],[25] The previous Nigerian studies have also shown the prevalence of obesity to be significantly influenced by socioeconomic status.[10],[11],[12],[13],[27]

The family history of adverse CVD events was present in 11.6% of our subjects. We found no similar studies on children; however, adult studies have demonstrated a high prevalence of adverse CVD events in the families of subjects with CVD risk factors.[29] Although the mechanisms are not fully known, there is substantial evidence that suggests that at least part of the higher risk in family members of CVD cases is due to familial aggregation of hyperlipidemia, reduced HDL-C levels, hypertension, hyperglycemia, or psychosocial factors.[30]

High low-density lipoprotein cholesterol (LDL-C) levels were present in 10.3% of our subjects while TC levels were high in 9.1%. These values are comparable to the 11.9% with high LDL-C and 11.8% with high TC levels reported in a Turkish school study by Uçar et al.[31] In contrast, only 4% of Tanzanian school children had high TC levels while 2% had high LDL-C levels as reported by Chillo et al.[24] The pattern demonstrated in our study could be attributable to recent socioeconomic growth with its attendant ills.

Another observation from the present study is the low mean HDL-C level in children from the low SEC. Although there are no available Nigerian studies for comparison, the findings here resemble those reported by Webber et al. among American school children in 1991[32] and also by Krawczyk et al. on Polish school children more recently.[33] Webber further demonstrated that even after controlling for socioeconomic and other factors, African-American children still had high abnormal TC and LDL-C and that this abnormality increased with increases in socioeconomic status.[32] It is a general consensus that low levels of HDL-C are harmful even if the TC level is only borderline elevated, making these children at risk for atherosclerosis and its consequences such as ischemic heart disease later in life.[34]

With increasing urbanization, CVD is predicted to overtake infectious diseases as the major cause of morbidity and mortality in the developing world by 2020, especially in young people.[35] Our finding of high levels of obesity, physical inactivity, hypertension, and dyslipidemia in primary school children is a pointer to the emergence of these factors in an environment hitherto dominated by undernutrition and infectious diseases.[1],[2],[3],[4],[5] Many reasons have been proffered for the rise in CVD risk factors in developing countries. Factors such as the decline of school sports, increase in indoor games (computer, video, and phone) coupled with changes in diet from traditional high fiber, low fat, and low salt diets to Western-style processed foods which are high in fats, salts, and sugars may be implicated.[4],[35]

The socioeconomic differences observed in the present study, with the most affluent students having significantly higher prevalence of CVDs, are in consonance with the tendency of the rich and middle class in developing countries to often be the first to adopt Western lifestyles. Our findings may, therefore, represent a snapshot of the “epidemiologic transition.”

Limitations of the study

Although the relationship between dietary patterns and cardiovascular risk has been documented, the present study was not able to do that because of limited funds. Thus, it would have been interesting to study that in the future to directly demonstrate its effect.


  Conclusions Top


Overall, this study underscores the important role of screening for CVD risk factors in school children, especially the modifiable ones, and highlights the need to begin primordial prevention strategies early such as the encouragement of physical exercise, school sports, and a healthy diet, that will ultimately serve to prevent adverse cardiovascular events in adulthood.

At the same time, it is important that parents are encouraged to personally adopt and practice healthy lifestyles at home, especially with regard to diet and physical activity. In this way, they become positive role models for their children and improve their own cardiovascular health.

Financial support and sponsorship

The Project described was supported by Medical Education Partnership Initiatives (MEPIN) project funded by Fogarty International Center, the office of AIDS Research and the National Human Genome Research Institute of the National Institute of Health, the health Resources and services Administration (HRSA) and the US Global AIDS coordinator under award number R 24 TW 008878. The content is the sole responsibility of the authors and does not necessarily represent the views of the funders.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

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



 

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