|Year : 2015 | Volume
| Issue : 2 | Page : 71-76
Hypertension and pre-hypertension among adolescents in Shimla, Northern India-Time to awaken
Anjali Mahajan1, PC Negi2
1 Department of Community Medicine, Indira Gandhi Medical College, Shimla, Himachal Pradesh, India
2 Department of Cardiology, Indira Gandhi Medical College, Shimla, Himachal Pradesh, India
|Date of Web Publication||30-Jul-2015|
Department of Community Medicine, Indira Gandhi Medical College, Shimla - 171 001, Himachal Pradesh
Source of Support: None, Conflict of Interest: None
Background: Hypertension is the most common, most potent universal contributor to CVD mortality. Primary prevention of hypertension and ischemic heart disease in adults necessitates a scientific evaluation of the predictors in childhood. BP studies in children provide important epidemiological information, which may help in controlling or modifying coronary risk factors.
Objective: 1) To determine the prevalence of hypertension and pre-hypertension among urban school adolescents in Shimla city. 2) To determine the association between hypertension and BMI for age in both the genders in the adolescents.
Materials and Methods: A total sample of 3385 students with 1665 females and 1720 male students was drawn for the purpose of the study. Socio-demographic profile, anthropometric and blood pressure readings were obtained. The prevalence of pre-hypertension, hypertension, obesity among the adolescents was determined.
Results: Overall mean SBP and DBP increased significantly with age in both the genders. Mean SBP (111.60 mmHg ± 11.43) and DBP (72.88mmHg ± 7.41) were higher in males in comparison to females in whom mean SBP and DBP were 109.91 ± 12.04mmHg and 71.84 ± 7.37mmHg, respectively. The prevalence of hypertension in females was more i. e., 13.1% in comparison to males 9.5%. However, the prevalence of pre-hypertension was nearly equal (11.0% in females and 11.3% in males). There was significant association of hypertension and BMI for age in both the genders.
Conclusion: There is an urgent need for public health measures to prevent high BP in children and adolescents from becoming another public health burden. There is trend toward higher prevalence of hypertension in school going children which reflects the changing scenario of cardiovascular diseases in current era due to changing lifestyle, dietary pattern, decreased physical activity and increase in obesity. Early detection and intervention in childhood can prevent adult hypertension.
Keywords: Adolescent, hypertension, pre-hypertension
|How to cite this article:|
Mahajan A, Negi P C. Hypertension and pre-hypertension among adolescents in Shimla, Northern India-Time to awaken. Nig J Cardiol 2015;12:71-6
| Introduction|| |
Hypertension is the commonest non communicable disease affecting both genders in all races.  It is the most prevalent cardiovascular disease risk factor worldwide. It has been shown that hypertension seen in children can progress into adulthood thus contributing to the increase in the cardiovascular morbidity and mortality in adults. , It has also been noted that even asymptomatic adolescents with mild blood pressure elevations can have target organ damage. Theyounger the age of onsetof hypertension the greater the reduction in life expectancy if left untreated.  Adolescents with high blood pressure have a significantly greater clustering effect of metabolic syndrome factors when compared to adolescents with low blood pressure. 
There is large disparity in prevalence of hypertension in children worldwide. This disparity can partly be attributed to age group (s) studied, economic status, nutritional and anthropometrics factors and the diagnostic criteria adopted, which necessitates the need for area-specific studies to derive local data and to document area-wise prevalence of hypertension. Although clinical hypertension occurs less frequently in children than in adults, ample evidence now supports the concept that the roots of essential hypertension extend back to childhood. Familial patterns of BP have been established from early infancy, and children with BP in the higher distribution percentiles are more likely to come from families with histories of hypertension. In the absence of any national data from India, it is necessary to make a beginning with a population that appears to be at the highest risk of developing hypertension- urban school children.
The present study therefore aims to detect the prevalence of hypertension and pre-hypertension and determine the association between hypertension and BMI for age in both the genders in the adolescent age group in Shimla city of Himachal Pradesh in North India.
| Materials and methods|| |
A descriptive, cross-sectional study was conducted among the school going adolescents of Shimla city in the State of Himachal Pradesh in North India. The sample size to be studied has been worked out as 3385 students (assuming prevalence of hypertension in children as 5%, with permissible error of 15%).
To start with, all primary, middle and senior secondary schools in Shimla City, from both the government and private sectors were enlisted. The schools to be included in the study from each sector were selected by simple random sampling technique (Lottery Method). As per the calculated sample size, almost proportionate number of students was selected for examination from each sector.
Prior permission from concerned school authorities was sought for this study. The examination of these students was done in a non-random manner in the serial order of the allotted roll numbers in their respective classes. For the purpose of participating in the study, the students were given consent forms to secure consent from their respective parents/guardian, in advance. Information regarding age was obtained from the students and also verified from the school records. Other information such as sex, family size, and history of hypertension in family and socioeconomic status was also obtained. A pre tested, structured and self-prepared questionnaire was administered to the study subjects in advance of the day of examination. Students with the help of their parents/guardians filled up the questionnaire. Children were called, in groups, for screening (as per class divisions) in a separate room where they were made to rest for 15 minutes to allay any anxiety or restlessness.
Weight was observed with the help of a standardized weighing machine after removal of shoes, jackets, heavier clothing and pocket contents. The weighing machine was tested daily for accuracy and calibrated against a set of standard weights.
Height was recorded with the help of a calibrated bar. For this the child was made to stand upright, with heels together and the weight borne evenly on both feet. Heels, buttocks and back were brought in contact with the vertical surface. The head was so positioned that the child faced forward with the Frankfurt plane (the line joining floor of external auditory meatus to the lower margin of orbit) and the bi-auricular plane being horizontal. Height was measured with the student bare footed. BMI was calculated as weight (Kg) divided by height (m²).
Children were encouraged to void urine before BP measurement. BP was measured using standard auscultatory technique and on the bare right arm with the student positioned in a seated posture, hands resting on the examination table and the cubital fossa supported at the heart level. The instrument used was a standard mercury sphygmomanometer.
An appropriately sized cuff was used (cuff width 40% of mid-upper arm circumference), with cuff bladder covering 80-100% of arm circumference and approximately two-thirds of the upper arm length, without overlapping. The bell of the stethoscope was placed over the brachial artery pulse, proximal and medial to the cubital fossa and below the bottom edge of the cuff (i. e. ≈2 cm above the cubital fossa). The systolic reading was taken as the mercury level at which the first sound (Korotkoff I) in a succession of sounds was heard. The diastolic reading (Korotkoff V) was taken, as the first level at which there was an absence of an expected sound. Three readings of BP of each child were taken at an interval of 5 minutes between each recording. The average of three consecutive readings was recorded as the average blood pressureof the child. The normative values of blood pressure were based on the Fourth Report  on the diagnosis, evaluation and treatment of high blood pressure in children and adolescents. In accordance with this report:
- Normal BP in children was defined as systolic and diastolic BP less than the 90 th percentile for gender, age and height
- High normal BP or pre-hypertension was defined as systolic and dastolicBP greater than or equal to the 90 th percentile but less than the 95 th percentile. Adolescents with BP levels greater than or equal to 120/80 mmHg but less than 95 th percentile were considered pre-hypertensive
- Hypertension was defined as SBP or DBP that is greater than or equal to the 95 th percentile
- Underweight:  A child was labeled as underweight when BMI was less than or equal to 5 th percentile for that age and sex
- Overweight:  A child was labeled as overweight when BMI exceeded 85 th percentile for that age and sex
- Obese:  A child was labeled as obese when BMI exceeded 95 th percentile for that age and sex. A child was labeled as centrally obese when waist circumference exceeded 95 th percentile for that age and sex
- Family history of hypertension was defined by the presence of hypertension (documented history of hypertension or current therapy with anti hypertensive medication) in parents, grandparents or siblings in the family.
Socioeconomic Status: Modified Prasad Classification was followed for the assessment of subjects under study.
Data collected was entered into the computer using a customized application with Sybase SQL Anywhere 5 at the back end as the Relational Database Management System. Simultaneously the data was cleaned for errors and omissions before transporting to MS Access 2000 DBMS and MS Excel spreadsheet 2000. Statistical analyses were performed using Healthwatchpro version 2.1 and statistical package SPSS version 10.0.1. Both descriptive and inferential statistics were used to analyze the data. A P value of less than 0.05 was considered as statistically significant.
| Results|| |
A sample of 3385 students comprising 1665 females (49.2%) and 1720 (50.8%) males was drawn for the purpose of the study. Of the total 3385 students, 1577 (46.6%) and 1808 (53.4%) were from government and private schools, respectively. Age wise distribution of Blood pressure in study subjects has been depicted in [Table 1]. Overall mean SBP and mean DBP was 110.77 mmHg (range 63-160mmHg) and 72.37 mmHg (range 39-106), respectively, in the studied age groups of 10-19 years [Table 1]. The overall mean SBP at 10 years was 99.81 ± 10.48 mmHg, which gradually increased to 116.64 ± 7.34 mmHg by the age of 19 years. Similarly overall mean DBP at 10 years was 66.09 ± 6.69 mmHg, which gradually increased to 75.82 ± 5.38 mmHg by the age of 19 years. The average annual increase in SBP from 10 to 19 years was 1.6 mmHg in females while it was 1.8 mmHg in males.
Similarly the average annual increase in DBP from 10 to 19 years was 0.9 mmHg in females while it was 1.2 mmHg in males. Generally males recorded a higher mean SBP and mean DBP than females [Table 2]. A total of 381 hypertensives detected in the present study 101 (3.0%) were studying in Government schools and 280 (8.3%) were in private schools. Out of 101 hypertensive students in Government schools, 59 were males and 42 were females. Out of 280 hypertensive students in private schools, 104 were males and 176 were females.
In the present study variance in mean SBP/DBP was signifi cant with variance in socioeconomic class. Overall mean SBP increased from 106.6 ± 12.2 mmHg in Social Class V to 113.3 ± 11.6 mmHg in Social Class I. Correspondingly, mean DBP increased from 70.6 ± 6.8 mmHg in Social Class V to 74.1 ± 7.3 mmHg in Social Class I [Table 3].
However, mean BP within the socioeconomic classes was relatively higher in males. Adopting the NHBPEP (National High Blood Pressure Education Program) criteria, in the present study conducted on adolescents, an overall prevalence of hypertension was observed to be 11.3%. Of the total 3385 students, 756 (22.3%) were found to have "highnormal BP" or pre hypertension with an almost equal prevalence existing in both the genders. The overall prevalence of hypertension was found to be higher in the age group 12-15 years [Table 4]. The study also revealed statistically signifi cant higher prevalence of hypertension in females (13.1%) than in males (9.5%).
|Table 4: Age and gender-wise prevalence of hypertension and pre-hypertension|
Click here to view
| Discussion|| |
Increase with age in mean SBP and DBP has been documented in various studies.  The present study further corroborates this.
In our study males recorded higher systolic and diastolic BP in comparison to the females. Similar finding of males recording higher mean SBP and DBP has been observed in a study in Karnataka.  Elsewhere, higher mean SBP in males and higher mean DBP in females have also been observed in different studies conducted on populations of 13-18,  15-24  and 15-25  years.
The reason for higher BP in males is that physiologically there is an average annual increase of about 2.0 mmHg in SBP from birth to the age of 20 years in males and about 1.0 mmHg in females. Between the ages of 10 and 14 years, however, this average increase is higher. This age-related increase in BP is attributable to increase in body mass. Similarly this average annual increase in DBP is about 0.5-1.0 mmHg through transition into adolescence from childhood in the case of both males as well as females. However, this rise in DBP is less marked than the corresponding rise in SBP, and this fact does not seem to vary between the genders.
In countries that are in transitional or pre-transitional stage of economic growth, higher levels of BP and higher prevalence of hypertension have been observed in upper socioeconomic groups.  In a study on adolescents in the age group 15-19 years,  SBP was significantly related to the socioeconomic status of the adolescents. Gilberts et al.  reported similar findings. Lifestyle differences between the upper and lower socioeconomic crusts such as eating habits, physical activity levels and tobacco use, etc., may have an indirect bearing on the BP levels in children.
The diversity in the prevalence of hypertension may be due to the difference in the age groups or racial subgroups (geographic, dietary and cultural influences) on which these studies were conducted or due to the difference in the criteria adopted in defining hypertension in these studies.
Presence of pre-hypertension in individuals is considered a precursor to hypertension and therefore warrants lifestyle modification. The study also depicted statistically significant association of hypertension with age. The overall prevalence of hypertension was found to be higher in the age group 12-15 years [Table 3]. This therefore, makes the age group of 12-15 years the most susceptible to the risk of hypertension. A similar study  has also reported higher prevalence of hypertension in children in the 13-15 years age group. This finding may be attributed to either the biological maturation or to the increase in body mass or simply to hormonal changes.
The study also revealed statistically significant higher prevalence of hypertension in females (13.1%) than in males (9.5%). Inter-alia, a plausible reason for such finding may be higher prevalence of overweight and obesity in females. Mangal et al.  has reported similar findings in respect of females. In a Nigerian Study, the prevalence of hypertension in the study population was 5.4% with male and female prevalence rates of 3.8% and 6.9%, respectively.  However, some studies depict higher prevalence among males,  while others depict no significant difference between the two genders.  In the present study, the prevalence of hypertension increased across the entire range of BMI values. This has been reported in numerous studies conducted on a variety of ethnic and racial groups, with virtually all studies reporting higher BP and/or higher prevalence of hypertension in obese compared to the lean. Rosner et al. reported a linear increase in the prevalence of diastolic hypertension with BMI in children of different race, gender, and age combinations. Similarly, Sorof et al.  reported an increased prevalence of systolic hypertension (based on a single set of measurements) as BMI percentile increased from the 5 th to the 95 th percentile. Our study also corroborates with the above findings, since there is significant increase in prevalence of hypertension with increasing BMI. Prevalence of hypertension increased from 6.2% in underweight to 13.2% in normal to 32.7% in overweight to 38.70% in obese children [Table 5]. Out of 101 (3.0%) overweight students, 30 (29.7%) students were found to be pre-hypertensive and 33 (32.7%) students were found to be hypertensive. Out of 31 (0.9%) overweight students, 10 (32.3%) students were found to be pre-hypertensive and 12 (38.7%) students were found to be hypertensive. Mohan et al. in a study in Ludhiana also found that there was significant increase in prevalence of hypertension with an increased BMI. 
The relationship between obesity and hypertension in childhood has been noted, though less extensively evaluated. It may occur due to increased cardiac output or excessive sodium intake or increased steroid production and alteration in reception for various presser substances.  In the present study, the association between family history and hypertension was significant in both the genders. Out of 3385 students, positive family history of hypertension was elicited in 516 (15.2%) subjects [Table 6]. Out of these 516 subjects, 75 (14.5%) were hypertensive and 125 (24.2%) were of high normal BP. The prevalence of hypertension was higher in those with positive family history. Many other workers , have reported similar finding. This suggests, there may be some genetic factors at play in the development of hypertension in children. It has been suggested that a major gene or polygenic pathways might be in operation during childhood, leading to high BP or pre-hypertensive states in those with positive family history of hypertension.
The findings in the present study underscore the urgent need for public health measures to prevent high BP in children and adolescents from becoming another public health burden. There is trend toward higher prevalence of hypertension in school going children which reflects the changing scenario of cardiovascular diseases in current era due to changing lifestyle, dietary pattern and decreased physical activity and increase in obesity. It would be logical to advise families with obese children to change their lifestyle with respect to diet, exercise and reduced salt intake to get their children accustomed to lifestyle that are favorable for maintenance of normal BP.
Studies of blood pressure in childhood may provide further clues to the etiology, prevention and treatment of subsequent hypertension in adulthood. The high yield of hypertension and pre-hypertension in the present study justifies the need for such studies in school children. Since it requires only the measurement of blood pressure, it would be appropriate if this is incorporated in the existing school health programs.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]
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