Comparative study of serum lipid profile between prehypertensive and normotensive

INTRODUCTION

The prevalence of hypertension and cardiovascular disease is rapidly increasing in developing countries.¹ This is likely related to changing lifestyle and increase longevity. The estimate shows that cardiovascular diseases have led to 1.59 million deaths in India in 2000 and this number is projected to increase in future.^1,2 Hypertension affects nearly 26 percent of the adult population worldwide.³ Hypertension is an independent predictor for cardiovascular diseases, cerebrovascular diseases and death.⁴

The seventh report of joint national committee on prevention, detection, evaluation, and treatment of blood pressure (JNC 7) defines hypertension as blood pressure >140/90 mmhg.⁵ Person with blood pressure above optimal levels, but not clinical hypertension, are defined as having “prehypertension”. Prehypertension is defined by JNC 7 report as systolic blood pressure (SBP) ranging between 120 to 139 mmHg and/or diastolic blood pressure (DBP) ranging between 80-89 mmhg.⁵ This range was earlier classified as high normal blood pressure. Classifying this range as prehypertension has placed many people who were earlier considered normal under this high risk category. Person with prehypertension have a greater risk of developing hypertension than do those with lower blood pressure levels.⁶ In addition, prehypertension itself is a risk factor for major cardiovascular events, independent of the other cardiovascular risk factors.⁷

Dyslipidemia also increases the rate of macrovascular complications (atherosclerosis).⁸ Studies have shown increased level of dyslipidemia in patients suffering with hypertension as compare to normal subjects.^9,10,11 Therefore increase level of blood lipids signify the increased cardiovascular risk in patients suffering from prehypertension. Studies also suggest that prehypertensives are more likely to progress to hypertension as compared to subjects with normal BP. Therefore early detection of this derangement and early interventions may arrest the progression of prehyertension to hypertension and prevent complications in individuals suffering from prehypertension. So the present study is undertaken to assess the lipid profile in prehypertensive and compare it with that of normal subjects and to study the correlation of blood pressure with lipid profile.

METHODS

The study was carried out by department of physiology. 100 subjects of age between 18 to 40 years were randomly selected from general population. The subjects were divided into two groups. Group 1consists of prehypertensive subjects and group 2 consists of normotensive subjects. Informed written consent of all the subjects participating in this study was taken. And institutional ethical committee approval was also taken. Subjects with the inclusion criteria such as prehypertensive as per JNC 7 criteria, non-smokers, and BMI in the range 18.5 kg/m² and less than 30 kg/m² were taken into the study group. While subjects with the history of smoking, alcohol intake, diabetes mellitus, or any other major illness and obese subjects were excluded from the study. Complete history taking and general and systemic clinical examination was done to rule out any clinical disorder likely to interfere with the study findings. Anthropometric parameters such as height, weight, waist circumference were measured and BMI was calculated.

Blood pressure was measured with the sphygmomanometer from the right arm of seated participant after five minutes rest and was recorded using 1^st and 5^th korotkoff sounds. The appearance of 1^st korotkoff sound was taken as systolic blood pressure (SBP) and 5^th korotkoff sound was taken as diastolic blood pressure (DBP). Three blood pressure measurements were taken and the mean of the last two measurements were used for analysis.

5 ml of venous blood was collected after overnight fasting of 12 hrs in all the subjects for estimation of serum total cholesterol, HDL cholesterol, LDL cholesterol, VLDL cholesterol, and serum triglyceride by standard enzymatic method.

Statistical analysis was done by using software SPSS version 20. All the parameters are measured in MEAN ± SD. Independent student t test has been used to find significance of study parameters between two groups. And pearson correlation has been used to find significance correlation between blood pressure and lipid profiles.

RESULTS

Comparative cross sectional study, with 50 cases with prehypertension and 50 cases of normal blood pressure, was undertaken to measure and compare the lipid profile among prehypertensives and normal subjects and to find the correlation of blood pressure with lipid profile among prehypertensives and normal subjects.

Comparison of basic characteristics like age, height, weight and BMI between two groups did not show significant different between the two group (p>0.05). The two groups were similar in terms of basic characteristics. (Table 1).

Results are presented in Mean ± SD. p value is significant at <0.05.

Comparison of blood pressure values between two groups showed significant difference. (p<0.001) (Table 2).

Results are presented in Mean ± SD. p value is significant at <0.05.

Comparison of lipid parameters between two groups is shown in Table 3. TC, LDL C, VLDL C and triglycerides values were significantly increased in prehypertensives as compare to normotensive subjects. While there was no significant difference in the value of HDL between two study groups.

Table 4 shows correlation of blood pressure with lipid parameters. There were statistically significant correlation between SBP and lipid parameters in prehypertensives except HDL. There was significant negative association between SBP and HDL in prehypertensives. While there were no significant correlation between SBP and lipid parameters in normal subjects. There were statistically significant correlations between DBP and lipid parameters in prehypertensives. While there were no significant correlation between DBP and lipid parameters in normal subjects.

Results are presented in Mean ± SD. p value is significant at <0.05.

Results are presented in Mean ± SD. p value is significant at <0.05.

DISCUSSION

The aim of the present study was to compare the lipid profile among prehypertensives and normal subjects and to correlate lipid profile with blood pressure. Prehypertension was associated with significantly higher total cholesterol, LDL C, VLDL C and triglyceride levels as compare to normal. HDL cholesterol value is significantly lower in prehypertensives than normal. This clearly shows that prehypertensives are at increased risk of cardiovascular events as compare to normal subjects.

The studies done in America also showed the association of prehypertension with risk factors such as hypercholesterolemia, diabetes mellitus, and obesity.⁶ studies done in Korean population showed that prehypertensives are more likely to have metabolic syndrome as compare to normals.¹² The result of present study also support the point that increased serum lipid parameters except HDL is seen in prehypertensives. This clustering of cardiovascular risk factors among prehypertensives suggests that person found to have prehypertension should be screened for other cardiovascular risk factors.

Before JNC 7 was published, these persons were considered to have normal blood pressure and were not recognised as potential candidates for cardiovascular intervention or risk reduction. But now we know, that the person with prehypertension are at increased risk of cardiovascular events. Prehypertensives are also at increased risk of progression to hypertension. The evidence that prehypertensives are at risk of cardiovascular events is now quite strong and some studies have begun to evaluate the role of pharmacological intervention.¹³

CONCLUSION

Lipid profile is altered in prehypertensives compare to normotensives. That’s why timely diagnoses and life style modification is required in prehypertensives.

ACKNOWLEDGEMENTS

We are thankful to all the subjects who participated in this study.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee

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