Prevalence and Determinants of Hypertension among Urban School Children in the Age Group of 13- 17 Years in, Chennai, Tamilnadu

Hypertension is a common disease associated with high morbidity and mortality. The disease is a silent threat to the health of people all over the world. It is suggested that hypertension has its origin in childhood but goes undetected unless specifically looked for during this period. Thus, early detection of hypertension and its precipitating or aggravating factors are important if one is to evolve measures so that complications of hypertension can be prevented.

Hypertensive children tend to have other medical problems, such as obesity, high blood lipids and/or diabetes mellitus. Coronary risk factors such as hypertension, smoking, physical inactivity, obesity and improper diet are fairly widespread. Cardiovascular diseases, particularly hypertension, account for high mortality in the form of cardiovascular strokes in countries like India, Taiwan and Japan [1]. In Indian adolescent school children, there is a high prevalence of obesity, hypertension, and hypercholesterolemia. Studies from Boston and Pennsylvania had commented that the role of hypertension as a risk factor is clear and familial aggregation of blood pressure and tracking phenomenon support the concept that children with hypertension are likely to be hypertensive as adults and will be at risk for early Coronary heart disease [2].

Though the data on Adolescents hypertension is very scarce across the globe, the National High Blood Pressure Education Programme (NHBPEP) of United States has recognized the presence of primary hypertension in children and adolescents [3].

With globalization bringing more lifestyle modifications, adolescents are exposed to multiple risk factors including obesity and also family history of hypertension [4]. Research in this area will help policy makers to see if there is a need for addressing this problem effectively in prevention and management of hypertension in children and adolescents. Early diagnosis of Hypertension is an important strategy in its control, which will be useful in tracking and effective treatment, to prevent further complications. Hence study was conducted to estimate the prevalence of hypertension in Chennai city and determinants of hypertension such as obesity, family history of hypertension, physical inactivity and life style associated with adolescent hypertension.

A cross sectional study was executed in Chennai-India including 400 samples with an equal distribution of 200 each from both private and public schools. Chennai has been divided into four educational zones namely North, South, Central and East zones. From each zone one school both from public and private sector using stratified random sampling method was selected. From each school fifty adolescent students (25 boys & 25 girls) between the age group of 13-17 who were eligible were selected by simple random sampling method and included for the study after obtaining their informed consent.

Blood pressure measurement

The Student was seated and relaxed. The cuff was placed on the right arm at the level of heart. On the day of measurement three readings were made at 0, 5 and 30 minutes. The average of three readings was taken as blood pressure of the individual.

Socio economic status

Socioeconomic status of the family in which respondent belonged was recorded using a well structured questionnaire. The questionnaire included details such as

Personal details

Age, religion, Standard, Type of curriculum Academic performance

Family details

Type of family, Parent’s education, occupation, income

Physical activities

Details of physical activity in school and indoor activities

Food details

Details of the junk foods, aerated drinks and frequency of their Intake.

Health information

Awareness regarding hypertension such as its definition causes and symptoms were included. Details of the presence of symptoms of hypertension and history of parent’s hypertension.

Anthropometric measurements

Such as height, weight, Waist-Hip ratios were recorded. Statistical analysis was done using SPSS version 10.

Hypertension

According to Joint National Committee VII (Indian scenario) 2003 [5] the following measurements of blood pressure are considered as normal, pre-hypertension and hypertension (Table 1).

Table 1: For - 13 years.

Adolescent Hypertension (AHTN) among school students

In this study 86 of the 400 participants were found to have hypertension. The prevalence AHTN was 21.5% and normal children were 314 (78.5%) (Figure1-3).

Figure 1: prevalence of Hypertension Both the systolic and diastolic BP was observed in 21 of these 86 hypertensives (24.41%) whereas 65 students (75.59%) had isolated systolic HTN. No students had isolated diastolic HTN.

Figure 2: Mean and standard deviation of systolic B.P was 110 mm/Hg and 12.65, Diastolic B.P was 65 mm/Hg and 8.62.

Figure 3: The prevalence among male was 67 (77.90%) and among females 19 (22.09%), which was found to be highly significant among males than females (p = 0.000).

BMI and HTN

Of the 321 normal weight students between (15^th and 85^th percentile), there were 53 (16.51%) hypertensive’s.

Eighteen were underweight below 15th percentile and there were no hypertensive’s among them.

Forty six were overweight with BMI between (85^th and 95^th percentile), 24 (52.17%) students were hypertensive’s, fifteen were obese with BMI above 95^th percentile 9 (56.25%) were hypertensive’s (Figure 4).

Figure 4: BMI and HTN.

Highly significant risk factors for HTN

Table 2 below shows the risk factor for development of HTN in this study, gender, standard, BMI, Obesity, Waist Hip ratio and family of hypertension which were found highly significant.

Table 2: Multivariate Analysis.

Other Medical Conditions

Out of 400 participants 386 were normal healthy individuals without taking any medications, two (0.5%) students were known hypertensive and on treatment. Six students were asthmatic, one had undergone coronary bypass surgery, and two girls reported irregular periods and five students complained of renal calculi and epilepsy that were on treatment.

Adolescent Hypertension is an emerging epidemic in India and the complications of hypertension like stroke, retinopathy, and CAD. The risk factors like obesity, family history of hypertension, Physical inactivity, academic performance, food habits and life style were studied using qualitative methods.

Prevalence of adolescent hypertension

The prevalence of Adolescent hypertension was 21.5% which indicates it is major public health problem and immediate intervention is needed. It has been varying widely in different Indian studies - from 0.46% to 11.9% In a study conducted in 2007 among school students of Adolescent age group in Mysore, the prevalence was 6.1% [6]. In another study done in Shimla, the prevalence was 20% (study period 2005 to 2006) [7].

The prevalence of isolated Systolic HTN in this study was 16.3%. This fact also has to be taken seriously as previous studies have shown that increase in Systolic hypertension alone itself interacts with other major risk factors such as high cholesterol and diabetes, which also increase with age, to amplify the age-related risk of cardiovascular events [8,9].

Gender

The prevalence among boys (31.75%, n=211) was found to be much higher than among girls (10.05%, n=189). The difference was highly significant (p=0.000) and goes along with the study done in Kerala in 2007 [10]. But some other previous studies revealed the gender variation to be much different. While the Mysore study [6] found no gender predilection at all, few other studies showed the prevalence high among girls [11]. Anyhow, the finding of the current study has to be taken as significant because the prevalence among boys is strikingly high.

Standard of study

The prevalence of hypertension was increasing with the class of study, it was the lowest among students of VIII standard and highest among X, XI and XII students. It was also statistically very significant (p=0.001). Though there was no previous data available in this regard, this higher prevalence may be attributed to the high stress level among the students of X, XI and XII due to huge academic burden and responsibilities.

Type of curriculum

No significant relationship between the type of curriculum followed by the students and the prevalence of hypertension (p=0.340) could be found. It may be taken as that irrespective of the difference in their curriculum, it seems all the students face the same level of stress.

Academic performance and hypertension

There was no significant relationship between hypertension and academic performance noticed. This may be because hypertension in its earlier stage is a silent condition without any symptoms and does not affect the studies and day to day activities of the person.

Physical activity

Current study could not find the any significant association between physical activity and hypertension. Spending more time in physical activities plays an important role in preventing and delaying the onset of hypertension. The association between physical activity and hypertension is an established fact. A study done by Gang Hu on relationship of physical activity and BMI to the risk of hypertension proved the protective effect of physical activity was observed in both sexes regardless of the level of obesity [12].

Anyhow the It may be perhaps due to the fact that only qualitative assessment was done. In depth analysis of the level of physical activity of the students could have revealed the association in a better way.

Parent’s education, employment and income

Details of parents’ education, employment status and income were asked, to assess the socio economic status of the family. There is no influence of SES with hypertension in this study. This is a contradiction to the result of an analysis done by Tanya M. Spruill, which says prevalence of hypertension was high among people belonging to low socio-economic status due to poor living conditions and high stress [13].

Food habits

The strong relationship between hypertension and diet habits has been well proved through various studies. Still the current study does not show a statistically significant relationship between food habits and HT. This may be because only qualitative assessment of food consumption was done. Anyhow non-significant relationship between diet and hypertension has also been arrived in another study conducted by M.R.Savitha et al. in Mysore [12].

Relationship between BMI and HTN

There is an overwhelming evidence in this study that the prevalence of HT is high among obese individuals (p=0.000), which is highly significant. This also confirms results of done by Jonathan et al. indicated obesity and overweight has major risk factors in hypertension [14]. John F Hall study also showed similar finding that chronic obesity also causes marked structural changes in the kidneys that eventually lead to a loss of nephron function, further increasing the arterial pressure. This study results also coincides with an Indian study done by Ruchika et al. in Delhi among school children, published in 2010 [15,16].

Waist-Hip Ratio and HTN

There is strong evidence in this study that obesity and overweight among males with waist-hip ratio more than normal is highly significant for higher prevalence of adolescent hypertension. This results agrees with similar finding of Ruchika goel et al. done in Delhi, increased in HTN with high W/H ratio and also Sinaiko et al. [11,16].

Familial history and HTN

The prevalence of hypertension was very high (41.86%) among children of hypertensive parents (either father or mother or both). This study strongly supports the fact that increase in prevalence of adolescent HT is highly significant among parents with hypertension. Similar relationship was found in Sharma et al. a study done among Delhi school students [17].

This study result also agrees with another work done by KA Jamerson et al. in U.S [18].

Awareness of HTN

Knowledge and awareness of hypertension are important factors in early diagnosis as well as achieving blood pressure control but the awareness of HTN was suboptimal as only 28.25% among the 400 students had some awareness about hypertension. As in general all the 86 subjects who were found to be hypertensive were absolutely asymptomatic and 2 of them were known hypertensive’s on medication, which further implicates the need to create knowledge and awareness among school students which is a growing public health problem. Similar result has been observed in a study done by Alexander et al. published in 2003 [7,19-31].

• All variables were assessed based on qualitative data as reported by verbally by the student. There were limitations in verifying the responses.

• Repeated examination on different occasions was not done due to time constraint.

• All measurements were made by single observer.

• The food habits were assessed based on frequency of consumption and responses were from the child’s memory, subject to recall bias.

• Physical activity was recorded as told by the children, no observation was done.

• The prevalence of hypertension among the adolescent age group was alarmingly high.

• Obesity, family history of HTN, gender, and increased waist/hip ratio were found to be the major determinants of Adolescent hypertension.

• There was no association found between Physical activity and food habits.

• There is no difference in prevalence in HTN among government, private schools and also with type of curriculum.

• Awareness about hypertension was very low among the study participants

• There was no association with Socio economic status and AHTN.

1. There is a need to create awareness among school students particularly in adolescent age group regarding hypertension and its complications.

2. School authorities should organize screening programmes in school particularly for HTN.

3. Parents should be educated about increasing prevalence of Adolescent hypertension.

4. Children should be educated about good life style and healthy food habits.

5. Awareness programmes should be conducted among school through Medias.

6. Parents should be educated to practice traditional and healthy dietary habits in their home.

7. Parents and teachers should be sensitized on over nutrition and the health hazards of chronic nutrition excess .

8. Periodic surveys should be done in schools on adolescent hypertension and tracking of blood pressure should be done, which will us helps in identifying the “at risk” group of children and adolescents, who can develop Hypertension in future period, so that preventive care can be provided for them.

9. Early detection and intervention is more important for AHTN, so, parents and children should have periodic heath checks up.

Author is grateful to Dr. Mayil Vahanan Natarajan, former Vice-Chancellor and present Vice-Chancellor Dr. D. Shantaram, Registrar Dr. Jhansi Charles of The Tamil Nadu Dr M.G.R Medical University for granting the permission to pursue this study. My sincere thanks to Dr. S. Joseph Maria Adaikalam, Lecturer, Department of Epidemiology for his encouragement and guidance. Author is thankful to Dr. Parameshwari Srijayanth, Dr. S. Kalpana, and Mrs. Valarmathi for their support throughout the dissertation. I wish to express my sincere thanks to my study participants who extended their full cooperation during this study. My special thanks to my family and friends.