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Table of Contents
Year : 2019  |  Volume : 16  |  Issue : 4  |  Page : 216-219

Prevalence of hypertension and associated risk factors in Suburban Tamil Nadu

1 Division of Non Communicable Disease, KMCH Research Foundation, KMCH Hospital, Coimbatore, Tamil Nadu, India
2 Division of Non Communicable Disease, KMCH Research Foundation, KMCH Hospital; Division of Non Communicable Disease, KMCH Research Foundation, Kovai Medical Center and Hospital, Coimbatore, Tamil Nadu, India

Date of Submission02-Nov-2019
Date of Acceptance04-Nov-2019
Date of Web Publication12-Dec-2019

Correspondence Address:
Krishnan Swaminathan
KMCH Research Foundation, KMCH Hospital, Coimbatore, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/am.am_68_19

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Background: Hypertension (HTN) is an important risk factor for cardiovascular mortality in India. HTN prevalence data are predominantly available for urban and rural populations in India but not in the mushrooming suburban areas. This study was conducted to estimate the prevalence of HTN and associated risk factors in suburban Tamil Nadu. Methods: In this Kovai Medical Center Hospital Non-Communicable Disease Study, we enrolled adults >20 years of age residing at Thadagam (suburban) in Coimbatore district, Tamil Nadu, India. All participants had a detailed questionnaire and anthropometric measurements. Blood samples were taken for glycosylated hemoglobin, nonfasting lipid profile, and serum creatinine. Prevalence of HTN (self-reported cases of HTN or systolic blood pressure ≥140 mm Hg and or diastolic blood pressure ≥90 mm Hg) was estimated. Multivariable logistic regression analysis was used to identify factors influencing HTN. Results: A total of 1030 participants were involved in this study. The prevalence of HTN was 47.1% in this area, with similar prevalence in both genders. The ratio of known HTN to newly diagnosed HTN was 1:1.3. Nearly 5% of adults between 20 and 39 years had HTN in this cohort. On multivariate logistic regression, after adjustment for age and sex, HTN was significantly associated with diabetes and atherosclerosis. Conclusions: This study identified a high prevalence of HTN in suburban region of Tamil Nadu. Aggressive screening protocols and targeted treatment are the need of the hour to reduce the burden of HTN and cardiovascular diseases in suburban India.

Keywords: Air pollution, cardiovascular disease, hypertension

How to cite this article:
Mohanraj S, Swaminathan K, Velmurugan G, Alexander T, Palaniswami NG. Prevalence of hypertension and associated risk factors in Suburban Tamil Nadu. Apollo Med 2019;16:216-9

How to cite this URL:
Mohanraj S, Swaminathan K, Velmurugan G, Alexander T, Palaniswami NG. Prevalence of hypertension and associated risk factors in Suburban Tamil Nadu. Apollo Med [serial online] 2019 [cited 2022 Dec 7];16:216-9. Available from: https://apollomedicine.org/text.asp?2019/16/4/216/272832

  Introduction Top

South Asia, particularly India, home to around 18% of the world's population, is currently in the midst of an epidemiological transition from infectious and nutritional illness to noncommunicable diseases (NCDs), especially cardiovascular disease, predominantly driven by a cluster of “traditional risk factors” such as diabetes, prediabetes, obesity, diet and lifestyle, hypertension (HTN), hyperlipidemia, and atherosclerosis. Individually, each of the above risk factors has huge healthcare, economical, and societal implications. Collectively, this “axis of evil” (as the above risks cluster together) is a disaster in the making for India and a “ticking time bomb” that will wreak the nation's health.

HTN, along with diabetes, is a key player that exerts a significant public health burden on cardiovascular health in India.[1] The burden of uncontrolled HTN in India is staggering. Estimates suggest that HTN is directly responsible for 57% of all stroke deaths and 24% of all coronary heart disease deaths in India.[2] In a systematic review of Global and Regional burden for disease and risk factors, HTN in South Asia ranks second in terms of attributable deaths and disease burden.[3] Adding to this is the dismal lack of awareness on HTN and the suboptimal control of disease in our rural and urban populations. Good control of HTN was estimated to be 6.5%–15% in rural India and 11.6%–28.7% in urban India in this systematic review.[3] To have 70%–85% of our hypertensive population with suboptimal control is a huge source of concern to the healthcare of our nation as this is an important risk factor for cardiovascular deaths.

The ICMR-INDIAB study in India has shown the prevalence of HTN to be 31.5% in urban and 26.2% in rural dwellers of Tamil Nadu.[4] However, over the past decade, there has been a population flow out from the cities and in from small towns and rural areas to the “suburbs.” This is due to a multitude of reasons including housing shortages in cities, better transport and the need for a more spacious environment. This area is forgotten in most studies as the focus is either on urban or rural areas. Our study aimed to estimate the prevalence of HTN among adults aged 20 years and older in a suburban area located at 15 km from Coimbatore city and identify unique factors responsible for the prevalence of NCD risk factors in this area.

  Methods Top

We conducted an NCD survey in the suburban population, Thadagam, situated at 15 km from Coimbatore, where brick-kiln is the main business and majority of residents are working in brick-kiln industries. The study was conducted from December 2015 to January 2016 in a staggered pattern over an 8-week period in this area. The study site was chosen due to ease of logistics, access to facilities to work out for the purposes of this study and ability to perform long term follow ups. The study population was recruited on the basis of a random sampling of households in the study areas. Before the start of study, pamphlets, loudspeaker announcements, meetings with community heads and volunteers were held in the community several times before and during the survey period. Volunteers and village heads were actively involved in encouraging people to participate in this study.

Data collection

Inclusion criteria were all adults >20 years of age native to study site, while excluded were subjects <20 years of age, pregnant women, and people not native to study site. The nativity was confirmed through proof of national identity document (ration card, driving license, or Aadhar card). The study was approved by the Local Ethics Committee, and informed consent was obtained from all the participants. Collected data were evaluated on a weekly basis, and feedback was sent to the study team in the field to correct any discrepancies.

The questionnaire of the present study was done in accordance with the WHO STEPs, which includes three STEPS; (1) sociodemographic characteristics, lifestyle, participant history, and family history of HTN and diabetes; (2) physical measurement including blood pressure, body height, weight, waist and hip circumference; and (3) laboratory investigation including venous blood samples for glycated hemoglobin (HbA1c), nonfasting lipid profile, and random blood glucose.

A detailed questionnaire was administered exploring the educational status, employment, alcohol intake, smoking status, pesticide exposure, family disease history, and medical history. Anthropometric measurements including body weight, height, and waist circumference were obtained from all participants. All participants had blood pressure measurement and carotid-intima thickness done using high-resolution B-mode ultrasound machines transported to the venue, by two final-year postgraduates from the Department of Radiology. Blood investigations included a random glucose (hexokinase/glucose oxidase-peroxidase/endpoint method), HbA1c (automated high-performance liquid chromatography [HPLC] method), creatinine, and nonfasting lipid profile. Fasting and post-meal glucose were not considered due to logistical issues.


Body weight was measured using an electronic weighing scale (SECA 813), height was measured by a stadiometer (SECA 208), and waist circumference was measured in centimeters using a nonstretchable measuring tape between the costal margins and the iliac crest at the end of expiration. Blood pressure was recorded using the electronic OMRON machine in the sitting position in the right arm (Model HEM-7130, Omron Healthcare, Singapore) on two occasions 15 min apart. We used the mean of the two measurements in analyses. Body mass index was calculated using the formula weight (kg)/height (m)2.

Clinical parameters

Serum and plasma samples were prepared from whole blood collected appropriately by the standard protocols. HbA1c was measured using an automated HPLC method (D-10-Biorad), glucose was measured using a Hexokinase/GOD-POD/endpoint method, lipid levels were measured automated analyzer (Abbott Architect ci8200), while uric acid and creatinine levels were measured by the Endpoint method (Abbott Architect ci8200). Hemoglobin was determined by SLS method (Sysmex XN).


HTN was defined as either having a history of HTN on medications or a systolic blood pressure of ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg on two occasions taken 15 min apart, in those without a history of HTN.

Statistical analysis

Data were tabulated on Microsoft Excel and transposed to SPSS for statistical analysis (IBM Corporation, Armonk, New York, USA). Data were analyzed using SPSS version 20. Multiple logistic regression model was used to estimate odds ratios for HTN and identify the risk factors associated with the HTN. A P < 0.05 was considered statistically significant.

  Results Top

A total of 1030 subjects participated in this study. Among these participants, 45.5% were males and 54.5% were females. The baseline characteristics are detailed in [Table 1]. The prevalence of HTN in this population was 47.1%. Among these hypertensive participants, 24.4% were males and 22.7% were females. Of these 485 hypertensive subjects, previous history of HTN was given by 210 (43.3%) subjects, with 275 (56.7%) new cases of HTN detected in this study group.
Table 1: Sociodemographic characteristics and biochemical parameters of the study subjects (n=1030)

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[Table 2] shows the results of the mean differences between the normotensive and the hypertensive cohorts. Hypertensive subjects were significantly older and had a higher body mass index, waist circumference, HbA1c, and carotid-intima thickness. [Table 3] shows multivariate regression adjusted for age and sex. HTN was significantly associated with diabetes and atherosclerosis in the adjusted model.
Table 2: Differentiation of mean (standard deviation) values for normotensive and hypertensive subjects

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Table 3: Multivariate analysis for risk factors of hypertension (Model-1: Unadjusted and Model 2: Adjusted by age and sex)

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  Discussion Top

Our study shows a staggering prevalence of HTN in a suburban part of Western Tamil Nadu. The prevalence was close to one-half of the adult population screened, with a significant number of undiagnosed or newly diagnosed HTN.

HTN exerts a significant burden on both the healthcare systems and cardiovascular burden in India.[1],[5] HTN packs a punch with some of the dismal statistics given below. HTN rates, as one of the most important causes of premature death worldwide,[6] rank second only to malnutrition in children as a cause of attributable deaths in South Asia [3] and directly are responsible for 57% of all stroke deaths and 24% of all coronary heart disease deaths in India.[2]

There is an alarmingly high prevalence of HTN in India varying between 20% and 59% depending on the geographical regions.[7],[8],[9],[10] In a systematic review and meta-analysis of prevalence, awareness, and control of HTN in urban and rural parts of North, East, West, and South India, around 33% of urban and 25% of rural Indians were hypertensive. Only one-third to one-fourth of this hypertensive population was treated; adding to this worry, only one-tenth of the rural and one-fifth of the urban Indian population have their blood pressure under control.[11]

With this background, we assessed the prevalence of HTN in Thadagam, a brick kiln suburban area, close to Coimbatore. Once an agricultural area, Thadagam had moved to the brick kiln business due to the booming construction industry around Coimbatore city. Our results showed a 47% prevalence of HTN in the adult population screened, much higher than similar prevalence data in the systematic review.[11] The prevalence between both genders were similar. On logistic regression, HTN in Thagagam area was significantly correlated with diabetes and atherosclerosis.

We speculate whether this high prevalence of HTN is linked to air pollution around Thadagam. There are 100 brick kilns in Thadagam with more than 300 chambers supplying unbaked bricks to these kilns. Such brick kilns are highly polluting, emitting gaseous pollutants, such as particulate matter (PM), sulfur dioxide, and carbon monoxide.[12] A meta-analysis of 17 studies suggest that both short-term and long exposure to such air pollutants increase the risk of HTN.[13] In addition, air pollution has been implicated in several adverse cardiovascular effects through oxidative stress, endothelial dysfunction, systemic inflammation, and autonomic dysfunction.[14] A meta-analysis also suggested that living within an area facing a chronic elevation of PM (PM2.5) leads to an approximately 10% increase in cardiovascular mortality.[15] Without proof, this is just speculation and hypothesis at this point of time. Further studies on the magnitude, duration, and frequency of air pollution in this area and its effects on NCD are planned by our study group.

There are several limitations to our study. This study sampling was convenient rather than stratified random sampling. This could have overestimated the prevalence of diseases as selection bias is a possibility. The hypothesis between air pollution in the local area and HTN cannot be justified based on speculation. These issues will be addressed in our follow-up study.

  Conclusions Top

We report a high prevalence of HTN in a suburban area of Tamil Nadu with a significant amount of air pollution Our data highlight the urgent need for systematic studies to understand the cardiovascular risk factors' phenotype and novel environmental risk factors that are associated with HTN in all different demographical areas in India.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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Gupta R. Trends in hypertension epidemiology in India. J Hum Hypertens 2004;18:73-8.  Back to cited text no. 2
Lopez AD, Mathers CD, Ezzati M, Jamison DT, Murray CJ. Global and regional burden of disease and risk factors, 2001: Systematic analysis of population health data. Lancet 2006;367:1747-57.  Back to cited text no. 3
Bhansali A, Dhandania VK, Deepa M, Anjana RM, Joshi SR, Joshi PP, et al. Prevalence of and risk factors for hypertension in urban and rural India: The ICMR-INDIAB study. J Hum Hypertens 2015;29:204-9.  Back to cited text no. 4
Leeder S, Raymond S, Greenberg H, Liu H. A Race Against Time. The Challenge of Cardiovascular Disease in Developing Economies. New York: Columbia University; 2004.  Back to cited text no. 5
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Dutta A, Ray MR. Prevalence of hypertension and pre-hypertension in rural women: A report from the villages of West Bengal, a state in the eastern part of India. Aust J Rural Health 2012;20:219-25.  Back to cited text no. 9
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Anchala R, Kannuri NK, Pant H, Khan H, Franco OH, Di Angelantonio E, et al. Hypertension in India: A systematic review and meta-analysis of prevalence, awareness, and control of hypertension. J Hypertens 2014;32:1170-7.  Back to cited text no. 11
Skinder BM, Pandit AK, Sheikh AQ, Ganai BA. Brick kilns: Cause of atmospheric pollution. J Pollut Eff Cont 2014;2:112.  Back to cited text no. 12
Cai Y, Zhang B, Ke W, Feng B, Lin H, Xiao J, et al. Associations of short-term and long-term exposure to ambient air pollutants with hypertension: A systematic review and meta-analysis. Hypertension 2016;68:62-70.  Back to cited text no. 13
Sanidas E, Papadopoulos DP, Grassos H, Velliou M, Tsioufis K, Barbetseas J, et al. Air pollution and arterial hypertension. A new risk factor is in the air. J Am Soc Hypertens 2017;11:709-15.  Back to cited text no. 14
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  [Table 1], [Table 2], [Table 3]


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