Prevalence of Hypertension And Its Correlates Among School Girls In Bengaluru

Introduction

Raised blood pressure (BP) in childhood is associated with various short-term and longterm squeal which leads to premature mortality in adulthood.¹ There is substantial evidence that the risk for developing hypertension is established early in life.² Studies have shown that the atherosclerotic process begins as early as childhood and risk factors for cardiovascular diseases have been shown to progress from childhood to adulthood.³ Hence, valuable information can be obtained in the study of the "tracking" of blood pressure values from childhood to adulthood. The prevalence of hypertension in children amongst Indian studies varies from 1 % - 7%⁴ . The prevalence may be high in south India because of change in dietary habits and life style.⁴ The trend has been highly marked amongst the adolescents because of a variety of reasons, the most common ones being the increasing consumption of junk foods and physical inactivity, with television and computer having replaced the space of outdoor activities. These lifestyle trends have led to increased incidence of obesity and overweight amongst school going children. Many developing countries including India are now in phases of epidemiological transition due to increase in the burden of cardiovascular diseases (CVDs) and their risk factors such as hypertension.⁵ The risk factors for hypertension include obesity, family history of hypertension, change in dietary habits, decreased physical activity and increasing stress. Thus, early detection of hypertension and its precipitating or aggravating factors are important to formulate measures so that complications of hypertension can be prevented.⁶ The US National High Blood Pressure Education Program Working Group recommended BP measurements in children aged 3 years or older in routine health examinations for earlier identification and control of elevated BP in children.⁷ Studies on hypertension in childhood have an important added advantage that they may help in the early detection, control and possibly prevention of high blood pressure in adulthood, before its harmful sequelae can occur. This study was envisaged keeping in view the substantial prevalence of the problem among school children in India and paucity of literature among school girls; the importance of early identification of children with hypertension, proper evaluation and appropriate management to prevent serious long term complications.

Materials & Methods

A cross-sectional study was conducted among school girls in the age group of 6 -15 years in a selected girls’ school in Malleshwaram, Bengaluru. The study was conducted during 2016, after seeking permission from the school authorities. The sample size was estimated based on a study conducted by Borah et al, (2008) where it was observed that the prevalence of hypertension in school girls aged 5-14 years was 7.8%.⁴ For our present study, with a desired confidence level of 95% and an absolute precision of 2%, the sample required was 691 subjects. Allowing 10% for absenteeism, sample size worked out to be 760. Ethical clearance was obtained from Institutional Review Board (IRB) before starting the study. A list of all students (n=965) was obtained from school authorities. Complete enumeration of all the girls studying in the school was done. Sociodemographic details were collected through a predesigned, pretested, semi-structured questionnaire which was sent through the students to be filled by their parents. This semi structured questionnaire included questions about parent’s age, education, occupation, monthly income and parent’s history of hypertension. Written consent from parents was taken before examination of children. Height of children was recorded using a stadiometer (up to the nearest 0.5 centimetre). Students were made to remove their footwear, stand straight with heel, buttocks & upper back touching the vertical plane of the instrument with correct head alignment Weight was measured with digital weighing machine (to nearest 0.25 kilogram) without footwear and minimal clothing (school uniform)⁸ Zero error was checked after every ten measurements. The percentiles of height, weight and body mass index (BMI)was calculated as per Revised Indian Academy of Paediatrics 2015 growth charts for 5-18-year-old Indian children⁹ and identified as overweight if BMI percentile was ≥ 75 percentile, obese if BMI percentile was ≥ 95 percentile. Blood pressure was examined by auscultation in right arm, sitting posture, by using standardized, validated and calibrated mercury gravity sphygmomanometer. Standard methodology, as recommended by the Fourth Report on the diagnosis, evaluation and treatment of high blood pressure in children and adolescents, was used to measure blood pressure.¹⁰ An appropriate cuff size was used which is one with an inflatable bladder width that is at least 40 percent of the arm circumference at a point midway between the olecranon and the acromion.¹¹ The cuff bladder length covered 80 to 100 percent of the circumference of the arm.¹² The cuff size used for the school children ranged from 12.5 -14cm. Efforts were made to eliminate factors which might affect the blood pressure such as eating a heavy hot meal, consumption of coffee or tea, anxiety, crying and laughing and by making them sit down quietly for five minutes and explaining the procedure of examination to them. The systolic blood pressure was determined by the onset of the “tapping” Korotkoff-1 sound and the diastolic at its disappearance (Korotkoff-5).¹² Every 10th student’s blood pressure was measured again by another observer to check for inter-observer variation. A good agreement was found (kappa statistic 0.87) between inter-observer measurement of blood pressure.

The children were considered to be hypertensive if the systolic or diastolic blood pressure or both were equal to or more than the 95th percentile for height for age and sex. Pre-hypertension in children was defined as average SBP or DBP levels that are greater than or equal to the 90th percentile, but less than the 95th percentile.¹¹ Socio-3economic status was assessed by using modified B G Prasad classification 12 which takes into account monthly per capita income of the family. Attempts were made to reduce bias; measurement bias was reduced by using standardized instruments and methods for measurement of height, weight and blood pressure. Every tenth student’s blood pressure was measured again by another observer to check inter observer variation (kappa statistic 0.87).

Follow up

Following analysis of results, children whose blood pressure was more than 90th percentile was listed out. These children’s parents were invited for a meeting with the investigators to inform & educate about their children’s blood pressure status. Parents of 68 (32.3%) hypertensive children out of 210 (100%) who were invited came for the meeting. They were advised to get their child’s blood pressure recorded weekly by their paediatrician for confirmation and further management.

Statistical analysis

Analysis was done using SPSS Inc. Released 2009. PASW statistics for windows version 18.0 Chicago. Prevalence of hypertension and prehypertension was estimated as percentages with 95% confidence interval. A quantitative variable such as age was summarized in terms of mean and standard deviation. Categorical data was analysed and summarised in terms of percentages & its 95% confidence interval was estimated. Association of each of the categorical variables with hypertension status was assessed by applying chi-square test and factors were considered significant if P value < 0.05. Multiple logistic regression was done to find the independent factors associated with hypertension and pre-hypertension combined together.

Results

Of a total of 965 girls studying in the school, 905 (93.8%) were enrolled for the study after excluding 18 students who were not present on the day of examination. Among the parents, 422 (54.3%) of fathers and 396 (50.2%) of mothers were graduates, 218 (28.7%) of fathers were senior officials/ professionals and (378) 49.8% were clerks. Among the mothers, 600 (78%) of them were homemakers and 12.1% were senior officials/ professionals. Information about education 12.9% (n=127) and 11.8% (n=117) and occupation details 15% (n=146) and 13.9% (n=136) could not be obtained for fathers and mothers respectively. Among the participants, 548 (74.9%) belonged to upper/ upper middle class, 126 (17.2%) belonged to middle class & 58 (7.9%) belonged to upper lower/ lower class. Prevalence of hypertension among children whose mothers and fathers were professionals/ senior officials was 20 (21.5%) and 48 (22%) respectively. Prevalence of hypertension was 12 (20.7%) among children belonging to upper socioeconomic class. Association of hypertension with mother’s occupation, father’s occupation and socioeconomic status were tested which did not show any significance with P values 0.97, 0.24 and 0.83 respectively.

The mean (SD) age of girls was 9.9 years ± 2.04yrs. There were 409 (45.2%)in the pre-adolescent age group (6-9 years) and 496 (55.4%) of them were in adolescent age group(Table 1).The mean (SD) age of girls was 9.9 +- 2.04 years. The mean (SD) systolic blood pressure was 97.3 ±12.3 mmHg& mean SD diastolic blood pressure was 65.9 ± 9.35 mmHg.

Among the study participants, 76.8 % of them had normal blood pressure, 7.7 % (n=70) (95% CI;5.92 – 9.47) were in pre - hypertension group and 15.5 % (n=140)(95% CI;13.09 – 17.50) were in hypertension group. (Table 1). Among the pre-adolescent age group, 58 (14.2%) were hypertensive&44 (10.8%) were pre hypertensive and in the adolescent age group 82 (16.5%) were hypertensive &26 (5.2%) were pre hypertensive and the difference between the age groups was statistically not significant (P = 0.26) (Table 2)

Hypertension among children and parental history of hypertension did not show any statistically significant association (X 21.70,0.57; p= 0.19,0.57) (Tables 2).

Hypertension among children and parental history of hypertension did not show any statistically significant association (X 21.70,0.57; p= 0.19,0.57) (Tables 2).

The height percentile distribution of school children is as follows; 49 (5.4%) were ≤ 3 percentile (below normal), 842 (93%) were in 4 – 96 percentile (normal) range and 14 (1.6%) were ≥ 97 percentile (above normal). As for the weight percentile distribution of school children, 46 (5.1%) were ≤ 3 percentile (below normal), 838 (92.6%) were in 4 – 96 percentile (normal) range and 21 (2.3%) were ≥ 97 percentile (above normal). Compared to girls with normal height, weight and BMI, those who were 97 percentile or obese had higher prevalence of hypertension. However, those who were below =3 percentile of height, weight had lower prevalence of hypertension compared to normal height and weight.

There was statistically significant association between hypertension and increasing BMI percentiles P<0.001)(Table 3). The adjusted odds ratio was computed for the 3 variables (height, weight and BMI). Only BMI revealed a statistical significance for overweight 1.67 (1.13-2.46) and obese 4.19 (2.75-6.38) girls as compared to girls with normal BMI.

Parents of girls who were found to be pre hypertensive or hypertensive were invited to the school for a meeting, to inform and advise them about hypertension in their ward. Awareness about the condition was given and suggestions to go for confirmatory diagnosis follow up and management was given. They were given advice for lifestyle modifications like: reduction of additional salt in the diet and being physically active. On further follow up, we were informed that out of 68 (100%) participants who attended the meeting, 15 (22%) had consulted a paediatrician for further evaluation. (Seven children had one follow up visit, five children had two follow up visits, two children had three follow up visits, one child had four follow up visits & two children had five follow up visits)

Parents through the school authorities were advised to track the blood pressure of their children annually. Parents of the other 53 girls, who did not go for evaluation, were re-advised about the importance of regular measurements of blood pressure.

Discussion

The present study attempted to find out the prevalence of pre-hypertension and hypertension and their correlates amongst school girls aged 6-15 

years. Not many studies have been carried out exclusively among girl students of this age group. Perhaps this age group may be more amenable for lifestyle modifications through dietary and physical activity measures to prevent the early onset of hypertension.

Our study revealed that the prevalence of hypertension among girls aged 6 – 15yrs was 15.5% and pre-hypertension was 7.7% compared to the study by Borah et al where hypertension was found in 7.8% of girls.13 In a study conducted by Sharma et al, hypertension was identified in 62 (5.9%) of children and pre-hypertension in 130 (12.3%). Differential prevalence of hypertension across various studies maybe attributed to age differences, differences in study settings and categorization of blood pressure, number of readings taken. In our study means of two readings were taken on a single day. In our study the rates were higher, probably due to dietary and lifestyle habits.

A study done by Borah et al revealed girls had 104.2 ± 12.0 mean systolic blood pressure (SBP) than boys. In the present study mean SBP was 97.3+- 12.3 mm Hg. In our study also, a significant association between hypertension with increasing BMI, was seen. 63 (23.5% of overweight and 78 (46.2%) of obese girls were hypertensive. BMI was found to be an independent predictor of hypertension. Rates of elevated BP were significantly higher (46.5% vs 17%, P<0.001) among those with high BMI (overweight and obese) compared to those with normal BMI in a study by Sharma et al.¹⁴ The possible reason for the association of hypertension with increased BMI could be the occurrence of atherosclerosis.

In many children, hypertension is only diagnosed when it is severe or when they reach adulthood. However it is important to diagnose hypertension early and accurately to prevent the long term complications of untreated hypertension. Paediatric hypertension may be a diagnostic indicator for preeclampsia during the reproductive period. It is well known that consumption of extra salt in the diet is associated with hypertension during the later part of life¹⁵

In our study, we were not able to demonstrate an association between parental history of hypertension and hypertension in children. It may be due to the fact that we could not get information about the condition in 13.7% and 12.7% of fathers and mothers respectively. The other reason for lack of association could be that the information was elicited only though a note sent home through the students without confirmation of medical records. Those who said that they were not hypertensive perhaps might not have had a medical examination in the recent past. However, it had shown significant association in a study done by Yuvraj et al.¹⁶

Chen et al in their review article report that tracking of blood pressure from childhood to adulthood showed significant change in blood pressure compared to baseline value and concluded that childhood hypertension leads to hypertension in adulthood.¹⁷

A limitation of this study was that the information filled out by parents regarding monthly family income, parental history of hypertension may not be very reliable and could be incomplete. This explains the reason for not finding any association of hypertension among children with high socioeconomic status and parental history of hypertension. Only 94.6 % of girls on the rolls of the school were covered. Hence the blood pressure status of the remaining 5.4 % of girls was unknown. Details of physical activity and dietary habits of the students could not be collected. This may have provided us further insight on lifestyle factors.

Conclusion

Despite the limitations, a significant finding of this study is a high prevalence of pre-hypertension and hypertension among school girls between 6-15 years. Besides, the number of students whose BP was measured was quite large. Hypertension seems to be a substantial problem among school girls (15.5%). Hence, screening and early detection through strengthening of school health programmes, among school girls to prevent long term complications of hypertension, is warranted. Further studies could be undertaken, taking into consideration physical activity and dietary habits (including consumption of additional salt) of children which will help in understanding the risk of developing hypertension and for adopting effective preventive measures.