Association between Blood Pressure and Obesity Indices in Medical Students

As per World Health Organisation (WHO), Obesity is considered as one of the most common yet neglected public health problem both in developed as well as developing countries. Statistically, according to the 2012 WHO report, worldwide, one in six adults are obese and about 2-8 million individual deaths occur due to overweight or obesity every year [1]. Obesity due to its high morbidity and mortality risks is recognised as a disease itself. Obesity has a strong association with other metabolic disorders namely HTN, diabetes, dyslipidemia, CVD and even some forms of cancer [2].

Thus, obesity is the epidemic for young adults in developing country like India due to sedentary lifestyle, eating habits and inadequate physical activity. Obesity has been found to increase the risk of morbidities and mortalities, including CVD, diabetes, gallbladder disease, respiratory disease, cancer, arthritis and gout [3]. Central distribution of body fat suggests excessive deposition of intra-abdominal fat in other words known as abdominal obesity found to be one of the important predictors of CVD risk [4].

India, with 1.3 billion people is the second most populous country in the world and is currently experiencing rapid epidemiological transition. Industrialisation and urbanisation also contribute to increased prevalence of obesity. Studies from different parts of India have provided evidence of the rising prevalence of obesity [5].

Similarly, in 2010 in South Asia high BP was ranked as third most important risk factor for diseases. Also in India, cardiovascular health status and health care systems are substantially burdened by HTN. About 57% of deaths due to stroke and 24% of deaths due to Coronary Heart Disease are directly related to HTN. HTN is rated as one of the most important cause of premature death worldwide by WHO [6,7]. The co-morbidity of obesity includes diseases such as CHDs, HTN, stroke and certain type of cancer. So, the aim of present study was to study the association between BP and obesity indices in Medical students.

Materials and Methods

A cross sectional study was conducted on a group of 100 healthy young medical students.

Inclusion criteria: Subjects of both genders; aged between 18-25 years were recruited for the study after taking written informed consent. The study was approved by the Institutional Ethical Committee (KDMCHRC/IEC/2018/01) of KD Medical College Hospital and Research Center, Mathura, Uttar Pradesh, India. The duration of study was six months from January 2019 to June 2019.

Exclusion criteria: The subjects of Acute illness (Acute myocardial infarction, Hypothyroidism, Liver disorder, Renal diseases) and known cases of any chronic illness- HTN, diabetes etc., were excluded from the study.

Blood Pressure

Resting BP (Systolic and diastolic) were measured after a sitting rest of 15-30 minutes by using mercury sphygmomanometer in sitting posture. Pulse rate and % oxygen saturation were measured by using pulse oximeter in same sitting position [7].

Obesity Indices

Anthropometric measures: Weight and height were measured in accordance with National Health and Nutrition Examination Survey (NHANES) anthropometric measuring guidelines with help of weighing machine and stadiometer [8]. Waist circumference, chest circumference, hip circumference and WHR were assessed. Waist circumference was measured at level of umbilicus and hip circumference was measured at maximum protrusion of hip in standing position in centimetres with heals together at linen measuring tape. Three measurements was taken for each site and average score recorded as final [9]. TF, VF was measured. Also, SF and MF of (whole body, arm, trunk and leg) was measured by using an impedance based BCA {Karada Scan of Omron Healthcare (Body Composition Monitor HBF-701)} [Table/Fig-1] [10].

[Table/Fig-1]:

Bioelectrical Impedance Analyser (BIA) Modal (HBF-701).

Image was taken from the booklet of the instrument

Bioelectrical Impedance Analyser (BIA) produces a close estimate of fat mass in a wide range of body compositions. It is a non-invasive measurement of body composition and also has many advantages compared with other methods because it is inexpensive, simple, fast, safe, portable and easy to perform, as well as requires minimum operator training [11].

Statistical Analysis

The results are presented in percentages and mean (SD). The Pearson correlation coefficient was calculated. Those parameters found to be significantly correlated were entered in multivariate linear regression analysis. The p-value <0.05 was considered significant. All the analysis was carried out on SPSS 16.0 version (Chicago, Inc., USA).

Results

The present cross-sectional study investigated 100 subjects (mean age 20.42±1.35 years, range 18-25 years), including 29 males and 71 females. The anthropometric obesity indices, demographic characteristics and disease variables of the study population are shown in [Table/Fig-2].

[Table/Fig-2]:

Distribution of Mean and SD of Different study parameters.

Study parameters	Mean	SD	Minimum	Maximum
Age (years)	20.42	1.35	18.00	25.00
Height (cm)	161.44	8.21	134.00	193.00
Weight (kg)	59.59	11.73	38.80	108.60
Total body fat	26.14	6.85	12.20	50.00
BMI	22.83	3.78	16.70	33.20
VF	6.32	4.83	0.50	40.00
Whole body
Skin fat	19.11	5.74	8.50	34.80
Muscle fat	31.21	3.21	22.40	38.30
Arm
Skin fat	28.59	8.44	13.10	48.80
Muscle fat	36.93	5.62	18.10	57.30
Trunk
Skin fat	16.93	5.82	7.10	44.30
Muscle Fat	24.82	6.15	13.60	54.00
Leg
Skin fat	28.11	8.22	9.00	53.50
Muscle Fat	46.58	5.89	19.10	54.40
SBP (mmHg)	112.56	8.30	92.00	138.00
DBP (mmHg)	75.44	8.77	56.00	106.00
Pulse/Minute	85.15	11.19	58.00	100.00
O2 %	93.54	7.82	63.00	110.00
Chest size (cm)	32.05	2.85	26.00	43.00
Hip size (cm)	33.53	2.94	25.00	45.00
CHR	0.95	0.04	1.17	0.875
WHR	1.76	0.24	1.23	2.41

V Fat: Visceral fat; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; CHR: Chest hip ratio; WHR: Waist hip ratio; BMI: Body mass index

The correlations between SBP and obesity indices were summarised in [Table/Fig-3]. SBP and DBP were mildly correlated with some of the parameters summarised in above mentioned [Table/Fig-3].

[Table/Fig-3]:

Correlation of study parameters with Blood Pressure (BP).

Study parameters	SBP		DBP
	Correlation coefficient (r)	p-value	Correlation coefficient (r)	p-value
Total body fat	-0.03	0.73	0.16	0.11
BMI	0.29	0.003*	0.21	0.04*
VF	0.34	0.001*	0.23	0.02*
Whole body
Skin fat	0.12	0.22	0.08	0.40
Muscle fat	-0.17	0.08	-0.17	0.07
Arm
Skin fat	0.12	0.22	0.01	0.92
Muscle fat	-0.04	0.64	0.02	0.77
Trunk
Skin fat	0.08	0.37	0.16	0.11
Muscle fat	-0.04	0.64	-0.04	0.66
Leg
Skin fat	0.07	0.44	0.06	0.50
Muscle fat	-0.14	0.14	-0.12	0.20
Others
Pulse	-0.12	0.22	0.10	0.31
O2 %	0.27	0.005*	0.04	0.69
Chest size	0.27	0.005*	0.003	0.97
Hip size	0.27	0.005*	0.01	0.88
CHR	0.01	0.89	-0.05	0.11
WHR	0.30	0.002*	0.62	0.27

*Significant (<0.05); VF: Visceral fat; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; CHR: Chest hip ratio; WHR: Waist hip ratio; BMI: Body mass index

There was poor correlation of SBP and DBP with TF and the association was not significant. SBP and DBP were mildly correlated with BMI (p<0.05). And with the whole body VF, the correlation of SBP was moderate and significant. DBP was correlated with whole body VF and correlation was significant. But the whole body, trunk, leg SF and MF were not having significant correlation with SBP and DBP. With the pulse rate also, there was no significant correlation. Finger to heart distance was positively correlated with SBP (p<0.05) but no correlation with DBP. O₂ %, chest and hip size were positively correlated with SBP (p<0.05). But the correlation with DBP was not significant. Only whole body VF and WHR were significantly (p<0.05) affected in SBP [Table/Fig-4]. None of the parameters affected DBP except BMI and VF.

[Table/Fig-4]:

Regression analysis SBP as outcome.

Parameters	Beta coefficient	p-value
(Constant)	54.08
BMI	0.38	0.53
VF	0.57	0.005*
O2%	0.07	0.52
Chest	-0.10	0.87
Hip	0.19	0.73
WHR	10.09	0.002*

*Significant; VF: Visceral fat; WHR: Waist hip ratio; BMI: Body mass index

Discussion

One of the leading risk factor for chronic arterial HTN is obesity [12]. Various efforts have been made by previous studies to find a correlation between various anthropometric index and BP and also incidence or prevalence of HTN when used to define obesity. A positive correlation was found between the prevalence of elevated BP and increasing adipose tissue by Mark AL et al., [13]. It was stated by Fuchus FD et al., that prediction of the incidence of HTN was even better with the correction of waist by stature or hip circumference than that of BMI [14]. Also, there were claims by Ghosh JR and Bandyopadhyay AR that both SBP and DBP as continuous variables have a stronger correltaions with BMI and WC than with other anthropometric indices [15]. Also, in the present study VF and BMI was significantly correlated with SBP and DBP [Table/Fig-3]. Obesity or excess relative weight is found to be associated with increased risk of disease morbidity and mortality [16]. BMI is widely accepted as one of the best indicator of nutritional status in adults [17,18] The importance of BMI and skinfolds has been recognised for estimating CVD risk factors, particularly due to their positive association with HTN [19]. Amongst the adult Brazilian men there was a significant linear correlation between both SBP and DBP for all anthropometric measurements and with higher BMI, WC and various skin fold locations there was increase in BP seen [20]. A significant positive correlation of BMI with SBP and DBP was earlier reported by many investigators [19,21,22]. Some studies suggested that general adiposity was more strongly correlated with BP [23,24], while other studies suggested central or visceral adiposity was more strongly correlated with BP than general adiposity [25,26]. VF is an important component and has been shown to be associated with a greater cardio metabolic risk, as compared with subcutaneous fat and other obesity measurements, including BMI [27-29]. But in the present study, there was no significant correlation of BP (SBP/DBP) with TF and SF or MF of different regions (whole body, arm trunk, leg). VF and WHR were significant predictors of change in SBP [Table/Fig-4]. Kurniawan LB et al., demonstrated that BW, BMI, WC, BF and VF had a significant correlation with insulin resistance but BW, BF and VF had a slightly better predictor value [30]. Bluher S et al., reported that BMI and WC were best predictors of cardiometabolic comorbidities in obese pubertal adolescents [31]. The WC was strongly associated with glucose and lipid disturbance in obese subjects.

Limitation(s)

Sample size in the study was small, including only healthy young adult population, thus for external validity of results, further study on a larger population including a wider age group of individuals is suggested.

Conclusion(s)

Present study conclude that BMI, VF and WHR had significant correlation with systolic and diastolic BP. VF and WHR were significant predictors of change in SBP. So, fat management is necessity for BP management.

V Fat: Visceral fat; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; CHR: Chest hip ratio; WHR: Waist hip ratio; BMI: Body mass index*Significant (<0.05); VF: Visceral fat; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; CHR: Chest hip ratio; WHR: Waist hip ratio; BMI: Body mass index*Significant; VF: Visceral fat; WHR: Waist hip ratio; BMI: Body mass index

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