European Journal of Cardiovascular Medicine

INTRODUCTION

Diabetes mellitus and hypertension are two of the most common non-communicable diseases (NCDs) worldwide and frequently occur together, forming a dangerous combination that markedly increases the risk of cardiovascular disease, stroke, and chronic kidney disease.[1] The global prevalence of diabetes among adults has risen sharply over the past three decades, and India, often referred to as the "diabetes capital of the world," bears one of the largest burdens of this disease.[2] It has been estimated that hypertension coexists in nearly 1.5 to 2 times more diabetic patients than in the general non-diabetic population.[3].

Type 2 Diabetes Mellitus (T2DM) accounts for more than 90% of all diabetes cases and is closely linked with hypertension through shared risk factors such as obesity, insulin resistance, sedentary lifestyle, and dietary imbalance.[4] Hypertension in diabetics accelerates the progression of microvascular complications such as diabetic nephropathy and retinopathy, and macrovascular complications including coronary artery disease and peripheral vascular disease.[5] The coexistence of these two conditions, often termed "diabetic hypertension," therefore poses a compounded risk to cardiovascular health and reduces overall life expectancy.[6]

Studies conducted in various parts of India have reported a wide range of hypertension prevalence among diabetics, from about 30% to more than 60%, depending upon the study setting, diagnostic criteria used, and population characteristics.[7],[8] Factors such as increasing age, longer duration of diabetes, obesity (general and central), family history of hypertension, physical inactivity, poor glycaemic control, dyslipidaemia, and excessive salt intake have consistently been reported as significant contributors to hypertension among diabetics in Indian studies.[9],[10] Additionally, rapid urbanization, changing dietary patterns with increased consumption of processed and salt-rich foods, and reduced physical activity in urban Indian populations have further fuelled this dual epidemic.[11]

Despite the well-recognized association between diabetes and hypertension, many patients attending diabetic clinics in India remain unaware of their blood pressure status, and hypertension often goes underdiagnosed and undertreated in this population.[12] Early identification of hypertension and its associated modifiable risk factors among diabetics is therefore essential for timely intervention and prevention of cardiovascular complications. With this background, the present study was undertaken to estimate the prevalence of hypertension and to identify its associated socio-demographic, behavioural, and clinical factors among Type 2 diabetic patients attending a tertiary care hospital.

Objectives

1. To study the socio-demographic, behavioural, and clinical factors associated with hypertension in these patients.

Study Design and Setting

A hospital-based, observational, cross-sectional study was conducted in the Department of General of a tertiary care teaching hospital.

Study Duration

The study was carried out over a period of twelve months, from [January, 2014] to [December, 2014].

Study Population

Patients diagnosed with Type 2 Diabetes Mellitus (as per American Diabetes Association criteria) attending the Medicine Outpatient Department and Diabetic Clinic of the hospital during the study period.

Sample Size

Considering an expected prevalence of hypertension among diabetics of 50% (based on previous Indian studies), with an absolute precision of 6% and 95% confidence level, using the formula n = Z²pq/d², the calculated sample size was 267, which was rounded off to 300 to account for non-response.

Sampling Technique

Consecutive sampling method was used to enrol eligible patients attending the outpatient department until the desired sample size was achieved.

Inclusion Criteria

Patients aged 30 years and above with a confirmed diagnosis of Type 2 Diabetes Mellitus for at least six months. • Patients willing to give informed written consent.

Exclusion Criteria

Patients with Type 1 Diabetes Mellitus or gestational diabetes. • Pregnant women. • Patients with known secondary causes of hypertension (renal, endocrine). • Critically ill patients unable to participate.

Study Tool

A pre-tested, semi-structured questionnaire was used to collect data on socio-demographic profile (age, sex, education, occupation, socioeconomic status as per modified B.G. Prasad classification), duration of diabetes, family history, dietary habits, physical activity (as per WHO Global Physical Activity Questionnaire), tobacco and alcohol use. Anthropometric measurements (height, weight, waist circumference) were recorded using standard techniques, and Body Mass Index (BMI) was calculated and classified according to the Asia-Pacific criteria for Indians.

Blood Pressure Measurement

Blood pressure was measured in a sitting position after 5 minutes of rest, using a calibrated mercury sphygmomanometer, following the WHO STEPS protocol. Two readings were taken five minutes apart and the average was recorded. Hypertension was defined according to Joint National Committee (JNC-7) criteria as systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg, or patients already on antihypertensive treatment.

Biochemical Investigations

Fasting and post-prandial blood glucose, glycosylated haemoglobin (HbA1c), and lipid profile were obtained from recent laboratory records or fresh samples were drawn wherever unavailable. Glycaemic control was categorized as good (HbA1c ≤7%) or poor (HbA1c >7%) as per ADA guidelines. Dyslipidaemia was defined as per NCEP-ATP III criteria.

Ethical Considerations

The study was approved by the Institutional Ethics Committee. Written informed consent was obtained from all participants, and confidentiality of the information was maintained throughout the study.

Statistical Analysis

Data were entered in Microsoft Excel and analysed using SPSS software version 21.0. Descriptive statistics were expressed as frequencies, percentages, mean, and standard deviation. Chi-square test was used to determine association between hypertension and categorical variables. Multivariate logistic regression analysis was applied to identify independent predictors of hypertension, with adjusted odds ratio (AOR) and 95% confidence interval (CI) calculated. A p-value of less than 0.05 was considered statistically significant.

A total of 560 patient data

A total of 300 Type 2 diabetic patients were enrolled in the study. The mean age of participants was 54.6 ± 9.8 years, with the majority (46.3%) belonging to the 51–60 years age group. Males constituted 56.7% of the study population. The mean duration of diabetes was 6.8 ± 4.2 years.

Table 1: Socio-demographic Characteristics of Study Participants (n=300)

Table 1 shows that the majority of the participants (46.3%) were in the age group of 51–60 years, and more than half (56.7%) were males. About two-thirds (64.0%) of the participants resided in urban areas.

Table 2: Prevalence of Hypertension Among Type 2 Diabetic Patients (n=300)

The overall prevalence of hypertension among the Type 2 diabetic patients studied was found to be 54.3% (163 out of 300 participants). Among the hypertensives, 68.1% were already aware of their hypertensive status and on treatment, while 31.9% were newly detected during the study.

Table 3: Association of Hypertension with Socio-demographic and Behavioural Factors

*Statistically significant (p<0.05)

On bivariate analysis, hypertension was significantly more prevalent among diabetics aged above 50 years, those with a family history of hypertension, physically inactive individuals, tobacco users, and those consuming a high-salt diet (p<0.05 for all). No significant association was observed between hypertension and sex of the participants.

Table 4: Association of Hypertension with Clinical and Biochemical Factors

DM = Diabetes Mellitus; WC = Waist Circumference; *Statistically significant (p<0.05)

Table 4 depicts that hypertension was significantly associated with longer duration of diabetes (>5 years), general and central obesity, poor glycaemic control, and presence of dyslipidaemia (p<0.05 for all variables).

Table 5: Multivariate Logistic Regression Analysis of Independent Predictors of Hypertension

*Statistically significant (p<0.05); OR = Odds Ratio; CI = Confidence Interval

On multivariate logistic regression analysis, age above 50 years, duration of diabetes more than 5 years, general obesity, and poor glycaemic control emerged as independent predictors of hypertension among the study participants, after adjusting for other covariates.

The present study was conducted to estimate the prevalence of hypertension and its associated factors among Type 2 diabetic patients attending a tertiary care hospital. The overall prevalence of hypertension among diabetics in this study was found to be 54.3%, which is comparable to the findings reported by Deepa et al., who observed a hypertension prevalence of 51.2% among Type 2 diabetics in a South Indian population.[13] Similarly, a study by Bhansali et al. conducted across various regions of India reported a prevalence ranging between 40% and 60% among diabetics, depending on the setting.[14] However, some community-based Indian studies have reported a comparatively lower prevalence of around 30–35%, which may be attributed to differences in study population, age distribution, and diagnostic criteria used.[15]

In the present study, hypertension was significantly more common among diabetics aged above 50 years, which is consistent with the findings of Gupta et al., who reported a significant rise in the prevalence of hypertension with advancing age among diabetics in a North Indian tertiary care setting.[16] Increasing arterial stiffness, decreased vascular compliance, and cumulative exposure to other cardiometabolic risk factors with advancing age may explain this association.[17]

A significant association was also observed between duration of diabetes and hypertension, with patients having diabetes for more than 5 years showing a significantly higher prevalence of hypertension. This finding is in agreement with the study conducted by Rao et al., who reported that a longer duration of diabetes was independently associated with hypertension due to progressive endothelial dysfunction and vascular damage induced by chronic hyperglycaemia.[18] Similarly, Mohan et al. in their study among urban Indian diabetics found that duration of diabetes exceeding five years was one of the strongest predictors of coexisting hypertension.[19]

Obesity, both general and central, emerged as a significant and independent predictor of hypertension in the present study, which corroborates the findings of Anjana et al., who reported a strong positive correlation between body mass index, waist circumference, and blood pressure levels among Type 2 diabetics in a multi-centric Indian study.[20] Excess adiposity, particularly visceral fat, contributes to insulin resistance, activation of the renin-angiotensin-aldosterone system, and sympathetic overactivity, thereby predisposing to hypertension.[21]

Poor glycaemic control (HbA1c >7%) was also found to be significantly associated with hypertension in this study, similar to observations made by Joshi et al., who reported that diabetics with poor glycaemic control had nearly twice the risk of hypertension compared to those with good glycaemic control.[22] Chronic hyperglycaemia is known to cause endothelial dysfunction, increased oxidative stress, and arterial stiffening, all of which contribute to elevated blood pressure.[23]

Physical inactivity, tobacco use, and high dietary salt intake were significantly associated with hypertension on bivariate analysis in the present study, findings that are well supported by the work of Reddy et al., who highlighted sedentary behaviour and unhealthy dietary practices as major modifiable contributors to the rising burden of hypertension among Indian diabetics.[24] Although family history of hypertension and dyslipidaemia showed significant association on bivariate analysis, they did not retain statistical significance on multivariate analysis in the present study, suggesting that their effect may be mediated through other correlated factors such as obesity and glycaemic control, a pattern also noted by Sharma et al. in a similar tertiary care based study.[25]

The high prevalence of hypertension observed in this study, along with the substantial proportion of newly detected cases (31.9%), underscores the need for routine and opportunistic blood pressure screening at every visit of diabetic patients to the outpatient department, as recommended by the Indian Council of Medical Research guidelines for the management of Type 2 diabetes.[26] Early detection and management of hypertension in diabetics can significantly reduce the risk of cardiovascular and renal complications, and improve overall quality of life.

Limitations of the Study

This being a hospital-based cross-sectional study, the findings may not be entirely generalizable to the community population. The cross-sectional design also precludes establishment of a temporal or causal relationship between the associated factors and hypertension. Additionally, dietary salt intake was assessed using a qualitative questionnaire rather than 24-hour urinary sodium estimation, which may be subject to recall bias.

The present study revealed that more than half of the Type 2 diabetic patients attending the outpatient department had co-existing hypertension. Age above 50 years, longer duration of diabetes, general and central obesity, and poor glycaemic control were found to be significant independent predictors of hypertension in this population. Given the modifiable nature of most of these associated factors, there is an urgent need for integrated screening programmes, lifestyle modification counselling, and stringent glycaemic and weight control measures among diabetic patients to reduce the dual burden of diabetes and hypertension and its associated cardiovascular complications.

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