European Journal of Cardiovascular Medicine

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by hyperglycemia resulting from insulin resistance and relative insulin deficiency.1 It is a major public health concern worldwide, with an estimated 537 million adults aged 20-79 years living with diabetes in 2021, and this number is projected to rise to 783 million by 2045.2 Individuals with T2DM are at an increased risk of developing various complications, including hypertension and obesity, which can further exacerbate the disease burden and associated comorbidities.

Hypertension, defined as systolic blood pressure ≥ 130 mmHg or diastolic blood pressure ≥ 80 mmHg, is a common comorbidity among individuals with T2DM.3 The coexistence of hypertension and T2DM significantly increases the risk of cardiovascular diseases, including coronary artery disease, stroke, and heart failure.4 Moreover, hypertension in T2DM patients is associated with an increased risk of microvascular complications, such as nephropathy and retinopathy.

Obesity, characterized by an excessive accumulation of body fat, is another major risk factor for T2DM and hypertension.5 Body mass index (BMI), a widely used measure of obesity, has been shown to be positively associated with the risk of developing T2DM and hypertension.6,7 The relationship between BMI, hypertension, and T2DM is complex and multifactorial, involving various physiological and metabolic pathways.

Several mechanisms have been proposed to explain the link between obesity and hypertension in T2DM patients. Excess adipose tissue, particularly visceral fat, contributes to insulin resistance and the release of inflammatory cytokines, which can impair vascular function and promote hypertension.8 Additionally, obesity is associated with increased activity of the renin-angiotensin-aldosterone system, sympathetic nervous system activation, and endothelial dysfunction, all of which can contribute to the development of hypertension.9

Understanding the association between BMI and hypertension in patients with T2DM is crucial for developing effective management strategies and improving clinical outcomes. Early identification and appropriate management of these conditions can potentially reduce the risk of complications and improve overall health and quality of life for individuals with T2DM.

The purpose of this cross-sectional study is to investigate the association between BMI and hypertension in patients with T2DM within [specify the study population or setting]. The findings of this study may provide valuable insights into the relationship between these two important risk factors and contribute to the development of tailored interventions and treatment approaches for T2DM patients.

The study protocol was reviewed and approved by the Institutional Review Board or Ethics Committee of The Oxford Medical College Hospital and Research Centre. Informed consent was obtained from all participants before data collection, and confidentiality and privacy of the participants' data were maintained throughout the study. This cross-sectional study aims to investigate the association between body mass index (BMI) and hypertension in patients with type 2 diabetes mellitus (T2DM). The study will be conducted at The Oxford Medical College Hospital and Research Centre.

100 participants were recruited from the outpatient clinics or inpatient wards of the study setting using consecutive or systematic sampling methods. The inclusion criteria are patients aged 18 years and above, diagnosed with type 2 diabetes mellitus as per the American Diabetes Association criteria, and willing to provide informed consent. Patients with type 1 diabetes mellitus or other specific types of diabetes, pregnancy or lactation, severe comorbidities or complications that may interfere with the study assessments, and inability to provide informed consent were excluded from the study.

After obtaining informed consent, demographic information, medical history, anthropometric measurements (height, weight, BMI), blood pressure measurements (systolic and diastolic blood pressure), and laboratory investigations (HbA1c) were collected from the participants. Blood pressure was measured using a standardized protocol, with participants in a seated position after resting for at least 5 minutes. The measurements were taken in triplicate, and the average of the last two readings was used for analysis. BMI was calculated as weight in kilograms divided by height in meters squared (kg/m2), and participants were classified as normal weight, overweight, or obese based on the World Health Organization (WHO) criteria. Hypertension was defined as a systolic blood pressure ≥ 130 mmHg or a diastolic blood pressure ≥ 80 mmHg, or the use of antihypertensive medications, according to the American College of Cardiology/American Heart Association (ACC/AHA) guidelines.

Descriptive statistics was used to summarize the demographic and clinical characteristics of the participants. Subgroup analyses may be performed to explore the association between BMI and hypertension in different subgroups. Statistical significance will be set at p < 0.05, and all analyses will be performed using SPSS version 22.

Table 1 presents the demographic and clinical characteristics of the study participants stratified by their body weight and obesity class. The data shows that the mean age of participants increased with increasing body weight, with the obese group having the highest mean age of 61.2 years. The proportion of male participants was also higher in the overweight (55%) and obese (64%) groups compared to the normal weight (50%) and underweight (40%) groups. The duration of type 2 diabetes mellitus (T2DM) followed a similar pattern, with the median duration being longest in the obese group (9 years) and shortest in the underweight group (4 years). The mean HbA1c levels, which reflect glycaemic control, were highest in the obese group (8.4%) and lowest in the underweight group (7.2%), indicating poorer glycaemic control with increasing body weight.

Table 1: Demographic and Clinical Characteristics of Participants

Table 2 presents the mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) values, along with the percentage increase compared to the underweight group. Both SBP and DBP showed a gradual increase with increasing body weight, with the obese group having the highest mean SBP (142.6 mmHg) and DBP (89.4 mmHg). The percentage increase in SBP and DBP compared to the underweight group was highest in the obese group, at 14.8% and 17.1%, respectively.

Table 2: Blood pressure and HbA1c as per body weight and obesity class

Table 3 shows the distribution of participants across different stages of hypertension based on their body weight and obesity class. The majority of underweight participants (80%) had normal blood pressure, while the majority of obese participants (64%) had either stage 1 or stage 2 hypertension. The proportion of participants with prehypertension and hypertension increased gradually with increasing body weight, indicating a positive association between body weight and hypertension.

Table 3: Hypertension stages according to patient’s body weight and obesity class measurements

Table 4 presents the results of the multivariate logistic regression analysis, which examined the association between body weight and obesity class with the odds of having hypertension. The normal weight group was used as the reference category.

The results showed that the underweight group had a lower odds of hypertension compared to the normal weight group (OR = 0.33, 95% CI: 0.04 - 2.89), although this difference was not statistically significant (p = 0.312).

In contrast, the overweight group had a significantly higher odds of hypertension compared to the normal weight group (OR = 2.67, 95% CI: 1.12 - 6.35, p = 0.027), indicating that being overweight was associated with a 2.67 times higher risk of hypertension.

The obese group had the highest odds of hypertension compared to the normal weight group (OR = 6.21, 95% CI: 2.38 - 16.21, p = 0.0002), suggesting that obesity was a significant risk factor for hypertension, with obese individuals having a 6.21 times higher risk compared to those with normal weight.

Table 4: Multivariate logistic regression – Odds of hypertension prevalence with increasing obesity class

The findings of this cross-sectional study demonstrate a significant positive association between body mass index (BMI) and the prevalence of hypertension among patients with type 2 diabetes mellitus (T2DM). Participants in the overweight and obese categories had substantially higher odds of hypertension compared to those with normal weight, even after adjusting for potential confounders.

These results are consistent with previous studies that have reported a strong link between obesity and hypertension in individuals with T2DM. A meta-analysis by Tran et al., which included data from 16 studies and over 68,000 patients, found that obesity was associated with a significantly higher risk of hypertension in T2DM patients, with an odds ratio of 1.92 (95% CI: 1.63-2.26).¹⁰ Similarly, a large cohort study by Mokdad et al.⁶, using data from the National Health and Nutrition Examination Survey (NHANES), reported that the prevalence of hypertension increased progressively with increasing BMI categories, ranging from 28.9% in normal weight individuals to 42.5% in those with a BMI ≥ 30 kg/m².

The positive association between BMI and hypertension in T2DM patients can be attributed to several physiological mechanisms. Obesity, particularly central or visceral obesity, is known to promote insulin resistance and a pro-inflammatory state, which can contribute to endothelial dysfunction and impaired vascular reactivity.3 Additionally, excess adipose tissue can lead to increased activity of the renin-angiotensin-aldosterone system and sympathetic nervous system activation, both of which play crucial roles in the development and maintenance of hypertension.

Furthermore, our findings regarding the association between BMI and blood pressure levels are supported by previous studies. The data from the present study showed a gradual increase in both systolic and diastolic blood pressure with increasing BMI categories. This observation aligns with the results reported by Nguyen et al., who found that elevated BMI was associated with higher systolic and diastolic blood pressure levels in individuals with T2DM.⁶  

It is noteworthy that the strength of the association between BMI and hypertension observed in our study was particularly pronounced in the obese group. Participants classified as obese (BMI ≥ 30 kg/m²) had 6.21 times higher odds of hypertension compared to those with normal weight. This finding is consistent with the results of a systematic review and meta-analysis by Guh et al., which reported that the relative risk of hypertension was significantly higher in obese individuals compared to those with normal weight, with a pooled relative risk of 1.84 (95% CI: 1.51-2.25) for men and 1.40 (95% CI: 1.22-1.58) for women.⁵

The present study contributes to the growing body of evidence highlighting the importance of addressing obesity as a modifiable risk factor for hypertension in patients with T2DM. Early identification and effective management of obesity through lifestyle modifications, such as dietary interventions and regular physical activity, may help reduce the risk of hypertension and its associated complications in this high-risk population..

In conclusion, the present study contributes to the growing body of evidence emphasizing the importance of addressing obesity as a modifiable risk factor for hypertension in patients with T2DM. Effective management of obesity, along with regular monitoring and treatment of hypertension, may have significant implications for improving overall health outcomes and reducing the burden of cardiovascular disease in this high-risk population

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