European Journal of Cardiovascular Medicine

Hypertension is universally acknowledged as a principal risk factor for cardiovascular diseases (CVDs) [1], with over a billion individuals globally affected. Even with advancements in understanding and treatment, it still causes around 8 million deaths each year [2–3]. New findings indicate a possible connection between hypertension and inflammation in the development and complications of atherosclerosis [4-5]. The numbers of hypertensive patients are expected to increase significantly when new guidelines are applied (i.e., systolic and diastolic blood pressure exceeds 130 mm Hg and 80 mm Hg, respectively, instead of 140 mm Hg and 90 mm Hg). Therefore, it will be fundamentally important to detect whether one is hypertensive and examine hypertension-induced organ disorders to prevent adverse outcome [6]. Worldwide, hypertension is estimated to affect more than 1 in 3 adults aged 25 and over, or about 1 billion people [7].

Hypertension is a growing problem in India and causes significant burden on the health system. Hypertension is one of the most important risk factors for cardiovascular diseases (CVD), particularly ischemic heart disease and stroke (sequelae of hypertension). Currently, it is estimated that 28.1% of all deaths in India were due to CVD and, high systolic blood pressure (SBP) was the single largest contributor (8.5%) to disability-adjusted life years DALYs [8]. There is a continuous relationship between the level of blood pressure and the risk of complications. With each increment of 20/10 mm Hg in the blood pressure range, CVD risk doubles with starting blood pressure of 115/75 mm Hg [9]. Of all death globally, 19.2% was attributed to high systolic blood pressure [10]. According to the 2019–2020 National Family Health Survey (NFHS-5), the prevalence of hypertension increased from 19% and 17%, respectively, in the previous round (2015–16) to 24% in men and 21% in women. According to statistics from the WHO NCD country profile (2018), 24% of Indian individuals aged 18 and over have high blood pressure. The prevalence of hypertension was nearly equal in men and women, with 24% and 23%, respectively [11].

By compromising endothelial function and encouraging atherosclerosis, inflammatory markers like C-reactive protein (CRP), interleukins (ILs), and tumour necrosis factor-alpha (TNF-α) have been associated with a poor prognosis in individuals with hypertension in CVD studies [12]. However, these markers' ability to accurately predict the course of people with hypertension is not entirely good. A straightforward, affordable, and generally available haematological measure, the neutrophil-to-lymphocyte ratio (NLR) has garnered increasing attention in recent years. Neutrophils and lymphocytes make up NLR, which represents a balance between immunological responses and inflammation. While lymphocytes play a significant role in controlling immunological responses, neutrophils are crucial for the acute inflammatory response [13].

The significant influence of NLR in people with hypertension is the subject of an increasing number of studies. A higher NLR is associated with a higher risk of hypertension, according to research by Xu JP et al [14]. A nine-year study conducted in Taiwan examined the relationship between NLR levels and the onset of hypertension, finding that higher NLR quartiles were substantially associated with a higher risk of developing hypertension, especially in older participants. According to these researches, NLR might be a more accurate predictive biomarker for hypertension than more conventional inflammatory indicators like platelet/lymphocyte ratio (PLR) or systemic inflammatory response syndrome (SIRI). Although these studies offer a preliminary understanding of the relationship between NLR and hypertension, research on the connection between NLR and mortality risk in hypertension adult is still limited.

In India there is very scarce literature available about Neutrophil to Lymphocyte Ratio in hypertension. Two studies are carried out, which are related to COVID 19 patient and not related to General Population. There is no study available about Neutrophil to lymphocyte ration in newly detected hypertension patient. In addition to this correlation of NL Ratio is never studied with Staging of Hypertension hence this is an area of interest.

The present cross-sectional observation study was conducted from May 2023 to November 2024 at Department of General Medicine, School of Medical Sciences & Research, Sharda Hospital, Greater Noida, Uttar Pradesh among 200 study subjects (100 newly detected hypertensive patients as per inclusion and exclusion criteria, with Age & Sex matched 100 controls). Formal approval from institutional ethics committee was obtained for conducting this study.

Sample Size calculation [11]:

Z = standard normal distribution, which is = 1.96

P (prevalence) = 24% or 0.24 (According to the data published in WHO NCD country profile 2018 prevalence of hypertension was found to be 24 % in India.) [13]

q = 1-P = 1- 0.24= 0.76

e (precision) = 6 % or 0.06

N= 194 which is rounded of to 200(100 newly detected hypertensive patients with Age & Sex matched 100 controls)

Sample Size has been calculated using Cochran’s formula-

Where:

1. e is the desired level of precision (margin of error)
2. p is the (estimated) proportion of the population which has the attribute in question,
3. q is 1 – p

Inclusion Criteria

Diagnosis - Hypertension was detected as per the American College of Cardiology (ACC) and the American Heart Association (AHA) criteria. (Year 2017)

1. Treatment naive and age more than 18 years.
2. Control cases who are normotensive for that age and sex match.

Exclusion Criteria

1. Hypertensive cases under treatment
2. Malignancy
3. Complication of Hypertension like Heart failure patients, coronary artery disease, stroke, Peripheral artery disease
4. Moderate and severe valvular heart disease
5. Diabetes Mellitus
6. Chronic kidney disease
7. Inflammatory disease
8. Thromboembolic and hematological disease
9. Drugs potentially interfere with NLR (like oral contraceptive drugs, anti-inflammatory drugs)
10. Abnormality in thyroid function test
11. Infections (like Bacterial, Fungal, viral)
12. Pregnant females

Study Procedure:

Using inclusion and exclusion criteria, the study population was chosen. The American Heart Association (AHA) and American College of Cardiology (ACC) guidelines for hypertension (2017) was followed while recruiting patients. After a thorough history was obtained, each patient had a clinical examination and evaluation. The chosen patients had their blood pressure taken twice on their right arm at 5-minute intervals in order to calculate the average of the two values [15]. Both the research group and the control group underwent blood investigations. Using traumatic venipuncture, blood samples were extracted from the cephalic vein and promptly combined with EDTA in a blood container. These samples were transferred to the Department of Pathology, where an automated haematology analyzer machine of Horiba Company (Yumizen H2500) was used

to estimate the whole WBC count, which includes the counts of neutrophils and lymphocytes. Comparisons between the study and control groups were made and there was a look at the relationship between the staging of hypertension in newly discovered cases and the Blood Neutrophil Lymphocyte Ratio (NLR). In the event of newly discovered hypertension, investigations were conducted in accordance with the study's approved Proforma as part of the basic workup. Participants will not incur any additional costs as a result of taking part in this study.

Statistical Analysis:

Data was entered in MS Excel spreadsheet program. SPSS v20 was used for data analysis. Descriptive statistics were elaborated in the form of means/standard deviations for continuous variables, and frequencies and percentages for categorical variables. Data was presented in a graphical manner wherever appropriate for data visualization using histograms, column charts for continuous data and bar charts/pie charts for categorical data and scatter plot to establish correlation. Group comparisons for continuously distributed data were made using independent samples ‘t’ test when comparing two groups, Pearson correlation test was used for group comparisons for categorical data. Statistical significance was kept at p < 0.05.

Out of 100 cases 54% were males while 46% were females. In the control group 57% were male and 43% were females. There was no statistically significant difference in both group (p=0.82). All the anthropometric parameters viz. height (cm), weight (kg) and waist circumference (cm) were comparable in both arms of the study.

Table 1: Baseline data among the study groups

Diabetic parameters viz. FBS (mg/dl), PPBS (mg/dl) and HbA1c were also comparable among the study groups (graph 1).

GRAPH 1: Comparison of diabetic parameters among the study subjects

Left ventricular hypertrophy (LVH) was present in 56% and 4% of the subjects in case and control group respectively. This difference was statistically significant (p<0.01) as shown in table 2.

Table 2: Left Ventricular Hypertrophy (LVH) comparison among the study groups

*: statistically significant

Mean Neutrophils%, Lymphocytes% in cases was found to be 66±6.30 and 27.38±3.55 which was significantly more as compared to control group. Mean NLR in newly detected Hypertensive cases was 2.55±0.61 while in cases it was found to be 1.98±0.48. When mean Neutrophils%, Lymphocytes% and NLR was compared using t test between case and control group, significant difference was revealed as p<0.05 (table 3). 

Table 3: Comparison of NLR among the study groups

*: statistically significant

Among the cases studied, stage 1 and stage 2 hypertension was reported in 21% and 79% of the cases respectively (graph 2).

GRAPH 2: Staging of hypertension among the cases

Mean NLR in stage 1 and stage 2 hypertension was 2.13±0.55 and 2.71±0.69 respectively showing increase in NLR as the BP rises. Hence mean NLR was significantly more in stage 2 hypertension as compared to stage 1 hypertension as p=007. (table 4). According to Pearson correlation test; significant positive correlation was found between NLR and staging of hypertension (r=0.44, p<0.01) i.e. with increase in NLR; SBP and DBP surges too.

Table 4: Comparison of NLR according to staging of hypertension among the cases

*: statistically significant

In order to prevent and treat hypertension, new treatments or therapies are required. Therapeutic strategies targeting low-grade inflammation may be useful in managing hypertension and reducing hypertensive damage because inflammation is a key factor in the pathophysiology of hypertension and increased blood pressure. Inflammation contributes to vascular remodeling and can promote the growth of smooth muscle cells in the vasculature. Many hypertensive models, including salt-sensitive hypertension, involve inflammation in the kidney. WBC, C-reactive protein, and interleukin-6 levels are a few inflammatory indicators that have been used to predict hypertension; however, the most of them are costly and time-consuming. In patients with cancer or coronary artery disease, NLR has been utilized to predict prognosis and survival as a simple and accurate measure of inflammatory status [16–20]. The study's objective was to examine the relationship between staging and the blood neutrophil to lymphocyte ratio in cases of newly diagnosed hypertension.

In both groups, there were significantly more males than females. They were 47.56±8.04 and 44.52±15.12 years old, respectively, in the case and control groups. The case and control groups' mean ages were similar, with a statistically insignificant difference (p>0.05). A similar pattern of age and gender was described in a study by Mistry HA et al [21]. In their study, S. Hong et al [22] found similar male dominance. They stated that the study participants' average age was 55.74 years.

Association Between NLR and Hypertension

The present study indicated that the mean levels of neutrophils, lymphocytes and NLR were higher in cases as compared to the control group. A significant difference (p<0.05) was found when the case and control groups' mean levels of neutrophils, lymphocytes, and NLR were examined using the t test. The study showed 21 % cases to be stage 1 hypertensives while 79% cases were stage 2 hypertensive. When NLR was studied with the staging of Hypertension it was found that the mean NLR in stage 1 % stage 2 hypertension was 2.13±0.55 & 2.71±0.69 respectively. This suggested that there is an increase in NLR as the BP rises. Hence mean NLR was significantly more in stage 2 hypertension as compared to stage 1 hypertension as p=007. The Pearson correlation test revealed a substantial positive link between NLR and hypertension staging (r=0.44, p<0.01), meaning that when NLR increases, so do SBP and DBP.

The body's immunological response and inflammation, which are intimately linked to the development of arteriosclerosis and target organ damage, may be the possible pathways connecting NLR to mortality in hypertension. By releasing oxidative stressors and inflammatory mediators, neutrophils may exacerbate endothelial cell damage, further impairing vascular function and raising blood pressure. Lymphocytes play a key role in controlling inflammation and immunological responses. Therefore, a higher NLR may indicate a more severe inflammatory state, which would worsen vascular damage and increase the chance of death [23–24]. Furthermore, neutrophils may cause reactive oxygen species to be released, which exacerbates oxidative stress. It has been demonstrated that oxidative stress plays a role in the pathophysiology of hypertension. Reactive oxygen species produce vasoconstriction in the vasculature and cause water and salt retention in the kidney. Neutrophils increase before hypertension develops in mice used in experimental models of the condition [25–27].

Numerous investigations have demonstrated that the pathophysiology of hypertension is greatly influenced by the adaptive immune response in particular. The immune system's regulatory arm is represented by lymphocytes, especially CD4+ T cells. Alloactivated T cell infusion for cancer treatment raises blood pressure in humans, and both humoral and cellular immunity are activated in pre-eclampsia, a potentially fatal pregnancy condition linked to elevated blood pressure. On the other hand, hypertension can be prevented by suppressing the adaptive immune system. The BP elevation brought on by angiotensin II—a hormone that stimulates thirst, encourages the kidneys to retain salt, causes vasoconstriction, and accelerates catecholamine release—in response to sodium and volume demands during adaptive immunity is mostly dependent on T cells. Experimental data has recently provided compelling evidence for a hitherto unknown role of T lymphocytes in hypertension. A well-known experiment by Guzik et al demonstrated that mice-lacking T cells (RAG-1/mice) have blunted hypertension and are protected from target-organ damage during angiotensin II infusion [28]. Human T lymphocytes, for instance, have been demonstrated to possess a functional active renin–angiotensin system.

In their study, S. Hong et al [24] found that hypertensive people with raised NLR levels had a significantly higher chance of dying from cardiovascular disease as well as all causes. Even after controlling for every possible confounding factor, the correlation was still substantial. This result is consistent with earlier studies, highlighting the significance of NLR monitoring in hypertensive patients and offering a more thorough approach to managing hypertension [24]. In their study, Mistry HA et al. [21] also found that the study group's neutrophil, lymphocyte, and platelet counts were considerably greater than those of normotensives. Additionally, the study group's neutrophil to lymphocyte ratio (NLR) was noticeably greater. There is a substantial positive association (p<0.01) between neutrophils, lymphocytes, and NLR and SBP, DBP, and MAP.

Our findings supported the research of Pusuroglu H et al [29], who found that isolated systolic hypertensive groups had noticeably higher NLR.

Additionally, Tatsukawa Y et al. [30] found a strong correlation between elevated neutrophil counts and the prevalence of hypertension in the Japanese population, particularly in women. They came to the conclusion that the main WBC component causing the elevated risk is neutrophils.

Higher NLR was discovered to be independently correlated with arterial stiffness by Park B et al [31], who came to the conclusion that high NLR is an extra metric to evaluate cardiovascular risk in clinical practice.

According to Cem O et al. [32], NLR is a sign of persistent low-grade inflammation and contributes to the development of ascending aortic aneurysms in hypertension patients. According to Belen E. et al. [33], NLR demonstrated a positive correlation with both SBP and DBP.

Brinda Srinivasagopalane et al. [34] studied clinical relevance of the NLR in hypertensives with varying degrees and lengths of hypertension. They found a statistically significant increases in neutrophil and lymphocyte counts along with a substantial increase in the NLR among hypertensives (p-value = 0.001). Additionally, they also demonstrated that those with stage 1 systolic hypertension and prehypertensive had higher NLRs. Vansh Marwaha et al. [35] carried out a study in 2024 showing mean NLR in individuals with elevated blood pressure, Stage 1, Stage 2 and hypertensive crisis. Their study suggested an increase in NLR initially for Hypertensive population.

Frequent NLR monitoring could contribute to a lower death rate. This is based on the idea that NLR is a measure of the body's stress and inflammation levels, and that a rise in it is linked to a number of negative health consequences. NLR monitoring aids in the early detection of inflammatory state changes, enabling prompt intervention strategies such anti-inflammatory medication, dietary optimization, and lifestyle enhancement that may lower the risk of inflammation-related mortality.

1. Sample Size and Population Bias: A small sample size reduces statistical power, which results in less trustworthy findings.
2. Cross-Sectional Study Design: This cross-sectional study of NLR and hypertension does not prove causation; rather, it merely offers a glimpse of the relationship. To determine if increased NLR is a cause or an effect of the course of hypertension, longitudinal investigations are required.
3. Variability in NLR: Temporary physiological or pathological situations (e.g., stress, acute infections) might cause fluctuations in NLR levels. A single measurement might not adequately capture the long-term inflammation linked to high blood pressure.
4. Hypertension Staging Criteria: Results may not be consistent if different guidelines (such as the American College of Cardiology and the European Society of Hypertension) categorize the phases of hypertension differently.
5. Limited Exploration of Other Biomarkers: The inflammatory profile of hypertension may be oversimplified if NLR is the only inflammatory measure taken into account, disregarding other inflammatory markers such as C-reactive protein and platelet-to-lymphocyte ratio.

The significance of NLR in hypertension will be better understood if these limitations are addressed by carefully planned, multicenter, longitudinal studies with bigger and more diverse populations, adjusting for confounders, and investigating processes.

Our study concludes by showing a strong correlation between raised NLR levels and an increased risk of hypertension in an adult population. It also demonstrated a rise in NLR levels as the severity of hypertension increases. Our findings suggest that neutrophils and lymphocytes may be implicated in inflammation, which may be a significant factor in the development of hypertension. These results could be helpful in elucidating the pathophysiological process of hypertension and in the creation of novel treatment strategies that target low-grade inflammation in order to manage hypertension and hypertensive damage. An elevated risk of unfavourable cardiovascular events linked to HT may be indicated by the measurement of NLR. To clarify the mechanism behind this connection, more future research with bigger sample numbers is required.

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