Title
Title: Assessment of blood pressure response to isometric hand grip exercise test in young adult students with parental history of hypertension- A cross sectional study
ABSTRACT
Background: It is found that 30 to 40 % of subjects with primary hypertension have genetic predisposition to acquire hypertension in future. They exhibit characteristic trait of autonomic hypervigilance with sympathetic overactivity. Static exercises can be used as a physical stressor to unmask the inherited vascular reactivity in these individuals.
Objective: Assessment of sympathetic overactivity in children with parental history of hypertension and compare it with controls of normotensive parents
Methods: A cross sectional study was conducted on 120 first year MBBS students of Jawahar Lal Nehru Medical College, Belagavi from January 2017 to December 2017. Institutional human ethical committee clearance was obtained prior to the study. The inclusion/exclusion criteria was defined & written informed consent obtained from participants. Students with parental history of hypertension were divided as study group (n=60) & students with no parental history of hypertension was grouped as control (n=60). Written informed consent from participants was obtained. The anthropometric and physiological parameters were recorded in them & sympathetic overactivity was assessed by rise in blood pressure response to IHG exercise test.
Statistical analysis: The data was analyzed using student t-test & p value <0.05 is taken as statistically significant.
Results: In the present study all the basal physiological parameters were high in study group and difference on pulse rate was statistically significant. The blood pressure response to static exercise was exaggerated in students with parental history of hypertension, indicative of sympathetic overactivity & possibility of acquiring future hypertension in these genetically susceptible individuals.
Conclusions: The present study concludes that normotensive children of hypertensive parents show sympathetic overactivity in the form of raised DBP and SBP on IHG exercise test .The latter is an age old standard noninvasive test used to unmask sympathetic dominance in genetically susceptible individuals.
Keywords: Autonomic hypervigilance, Sympathetic overactivity, Isometric hand grip exercise test,
Introduction: Hypertension is an emerging public health problem all over the globe. It is estimated to affect around one-quarter of adult population and is projected to be the leading cause of death by 2020 worldwide. Realizing the burden of the disease, World Health Organization (WHO) in the year 2013 declared “hypertension” as “World Health Theme” on World Health Day (7th April 2013) and also labeled hypertension as a “silent killer”.1,2 WHO defines hypertension as sustained rise in blood pressure with systolic blood pressure (SBP) and diastolic blood pressure ( DBP) of ? 140 mmHg and ?90 mmHg respectively (as per Joint National Committee, JNC 7th report ,2003) .3,4
The normotensive children with genetic susceptibility exhibit trait of unbalanced Autonomic nervous system (ANS) with early parasympathetic attenuation & sympathetic overactivity.5 They also exhibit abnormal characteristics like metabolic dysfunction (obesity, insulin resistance, dyslipidaemia), exercise induced rise in blood pressure, high basal blood pressure (hypertension) etc which causes cardiovascular and neurocognitive complications.6,7 Isometric hand grip test is an age old standard noninvasive test & act as a physical stressor to reveal the sympathetic dominance in genetically susceptible individuals.8
The present study was undertaken to assess sympathetic dominance in children of hypertensive parents and compare with children of non hypertensive parents.
Material and methods: The present cross sectional study was carried out over a period of one year, between january 2017 to december 2017 in the Department of Physiology, Jawaharlal Nehru Medical College, Belagavi. Ethical clearance from institutional human ethical committee was obtained. Total 120 students were recruited in the study after collecting sociodemographic details and history of parental hypertension in them. Following written informed consent from the participants & defining inclusion/exclusion criteria, normal healthy students between age 18-24 years were included in study group and students with h/o cardiovascular disease, on chronic medication for chronic illnesses, h/o alcohol and smoking habit and h/o drugs intake that modify sympathetic system were excluded.
Study group comprised of students with parental history of hypertension and control group comprised of children with no parental history of hypertension. The students were advised to have light beakfast, avoid tea/coffee 2-3 hours prior to the test & report to lab by 9:30am. Anthropometric details like height using krups weighing scale in centimeters, weight in Kg’s using stadiometer and BMI was calculated using quetlet’s equation. The classification of BMI followed was 9:
Normal BMI range = 18.5 to 24.9
Overweight=25.0 to 29.9
Obesity = ?30.0
Severe obesity = ?35
Basal pulse rate & blood pressure were measured with subjects in sitting position following 10 minutes. BP was recorded by manual method using Standardized mercury sphygmomanometer (diamond deluxe BP apparatus, Pune, India).
Isometric hand grip test 10: BP response to sustained handgrip i.e., Handgrip Dynamometer Test (IHG) using Jammar hand grip dynamometer inc.USA manufactured by INCO Ambala with values of 0-60 kgs was used to measure sympathetic response. Subjects were briefed about the instrument before conducting the test. Baseline BP was recorded from non dominant hand. The hand dynamometer is spring type with two needles, one remains at zero mark and the other needle depicts the maximal voluntary contraction i.e., values are b/n 0 to 60 kg. The subjects were advised to compress the handle of dynamometer with maximum effort using dominant hand for one minute. Three such readings were recorded with 30 sec gap in between to prevent fatigue. Mean of the three readings was calculated and T max was obtained. Thirty percent of the T max was calculated. Now the subjects were asked to maintain the same i.e., 30% of the T max for a period of 2 minutes. During these 2 minutes the BP was recorded from non dominant hand & second reading was taken following rest of 5 min after exercise.
Statistical analysis: The data was analyzed using student t-test & p value <0.05 is taken as statistically significant.
Results: The present cross sectional study was conducted to assess sympathetic reactivity in first year medical students between 18 to 24 years of age group with parental history of hypertension and compared it with students of non hypertensive parents. Total 120 students participated in study, out of which 60 identified with parental history of hypertension were categorized in study group and 60 students with normotensive parents were included in control group. Out of 60 students in study group, 81.67% students had parental history of hypertension in either of a parent & 18.33% students had a history of hypertension in both the parents. The two groups were almost identical on age, height parameters .Weight and BMI scores were comparatively high in study group than control group (Table 1). The resting state physiological parameters were high in study group and difference on pulse rate was statistically significant (Table 2).The DBP and SBP response to IHG test were statistically significant in study group(Table & graph 3 ; Table & graph 4) and both the parameters almost reached baseline in two groups after 5 minutes rest.
Table 1: Comparison of demographic and anthropometric measurements between study and control group
parameters Study group (n=60) Control group (n=60) p-value
Age 18.95 ± 1.13 18.83±0.87 0.5261
Height (cm) 164.12 ± 8.38 166.38 ± 8.99 0.156
Weight(kg) 64.60 ± 13.10 63.13 ± 13.41 0.546
BMI 24.03 ± 4.17 22.75 ± 3.80 0.081
Table 2: Comparison of baseline physiological parameters between study & control group
Baseline physiological parameters Study group (n=60) Control group(n=60) P-value
PR 82.50±8.90 79.07±8.45 0.032*
DBP 74.65±5.86 74.33±7.80 0.802 SBP 111.10±10.50 109.80±11.23 0.514
*p< 0.05
Table 3: Comparison of DBP response on isometric hand grip test – IHG test in study and control group
DBP (mmHg) Study group(n=60) Control group (n=60) P-value
Baseline 74.65±5.86 74.33±7.80 0.802
During IHG 98.90±11.26 89.52±9.88 0.0001*
After 5 Minutes 75.40±6.95 73.20±5.52 0.058
*P<0.05
Graph 3: Comparison of DBP response on Isometric hand grip test – IHG test in study and Control group
*p<0.05
Table 4: Comparison of systolic blood pressure response on isometric hand grip test– IHG test in study & control group
SBP(mmHg) Study group (n=60) Control group(n=60) P-value
Baseline 111.10±10.50 109.80±11.23 0.514
During IHG 142.73±17.40 129.37±12.73 0.0001*
After 5 Minutes 110.17±9.31 108.60±11.03 0.402
*P<0.05
Graph 4: Comparison of systolic blood pressure response on isometric hand grip test– IHG test in study & control group
*p<0.05
Discussion:
The present study was carried out to assess sympathetic response to IHG exercise test in children of hypertensive parents. The BMI score, resting PR & BP was higher among children with parents history of hypertension. Many studies have found significant rise in BMI & SBP in the genetically susceptible individuals who inherit these traits as recessive inheritance from either or both parents suffering from hypertension.11The underlying mechanism was explained on the basis of increased sympathetic activity in these children with high plasma catecholamine levels before exercise.12 The existing vasoconstriction & retention of sodium due to increased renal sympathetic activity is further exaggerated by high BMI.13
In the present study there was statistically significant increase in DBP & SBP during isometric handgrip-test. Rise in systolic & diastolic blood pressure with hand grip dynamometer is an indicator of increased sympathetic activity.14 The increased afterload to the heart due to constriction of blood vessels in exercising muscles and increased peripheral vasoconstriction mediated through adrenergic receptors of sympathetic nervous system is responsible for rise in DBP during IHG exercise. The muscle sympathetic nerve activity, which is under the control of baroreflex shows reduced sensitivity among the children of hypertensive parents, which leads to increased sympathetic vasomotor tone & inturn rise in BP.8
Conclusion: The sympathetic reactivity was higher among the children with parental history of hypertension. Isometric hand grip test is an age old standard noninvasive test used to unmask sympathetic dominance in genetically susceptible individuals. Other noninvasive tests can be used to confirm sympathetic overactivity and generalize the findings to larger population. The periodic evaluation & lifestyle modification measures shall be of significant value in reducing the morbidity and mortality associated with the disease in these future health care providers
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