Prevalence and Covariates of Undiagnosed Hypertension in the Adult Population of Puducherry , South India

Among 856 participants, 27.6 percent were hypertensive and 57 percent pre-hypertensive; the magnitude of both stage 1 and stage 2 hypertension increased with the age. Of the hypertensives, 26.3 and 28.7 percent were from rural and urban area respectively, whereas in pre-hypertension the corresponding figures were 61 and 53.4 percent. Significantly increased risk of hypertension was noted among adults with increasing age, having less than six members in the family, suffering from obesity (general and abdominal obesity) and living sedentary life. On the other hand, the probability of having increased risk of prehypertension was significantly higher among adults living in the rural areas, having non-vegetarian dietary habit, suffering from obesity (general and abdominal obesity), living sedentary life and having family history of hypertension. Multivariate logistic regression however showed significant correlation of hypertension with increasing age, sedentary lifestyle, tobacco addiction and obesity (general and central). Significant correlates of prehypertensive were rural residence, sedentary living habits, Corresponding Author: Dr. Ranabir Pal, M.D Professor, Community Medicine, Sikkim Manipal Institute of Medical Sciences, 5th Mile, Tadong, Gangtok, Sikkim, India-737 102 Email: ranabirmon@yahoo.co.inf Medical Sciences, 5th Mile 102


Material and Methods
A population based cross-sectional study was carried out in the field practices area of Department of Community Medicine, Mahatma Gandhi Medical College and Research Institute without intervention.

Results
Among 856 participants, 27.6 percent were hypertensive and 57 percent pre-hypertensive; the magnitude of both stage 1 and stage 2 hypertension increased with the age.Of the hypertensives, 26.3 and 28.7 percent were from rural and urban area respectively, whereas in pre-hypertension the corresponding figures were 61 and 53.4 percent.Significantly increased risk of hypertension was noted among adults with increasing age, having less than six members in the family, suffering from obesity (general and abdominal obesity) and living sedentary life.On the other hand, the probability of having increased risk of prehypertension was significantly higher among adults living in the rural areas, having non-vegetarian dietary habit, suffering from obesity (general and abdominal obesity), living sedentary life and having family history of hypertension.Multivariate logistic regression however showed significant correlation of hypertension with increasing age, sedentary lifestyle, tobacco addiction and obesity (general and central).Significant correlates of prehypertensive were rural residence, sedentary living habits,

Background
Hypertension is a major contributor to the global morbidity burden with devastating downstream outcomes with heavy financial burden on scarce health resources 1 .Hypertension is reported to be the fourth contributor to premature death in developed countries and the seventh in developing countries 2 .According to Kearney, worldwide reports indicate that nearly 1 billion adults (more than a quarter of the world's population) had hypertension in 2000 with a prevalence rate of 26.4 percent, and this is predicted to increase to 1.56 billion by 2025 and a prevalence rate of 29.2 percent 3 .The prevalence rates in India are now almost comparable to those in the USA 4 .Prevalence of HTN in people aged ≥ 20 years by world region and gender in 2000 and 2025 showed that in India in 2000 the combined urban and rural prevalence was 20.6 percent among males and 20.9 percent among females and in 2025 the projected rate will be 22.9 percent among males and 23.6 percent among females 3 .Pre-hypertension also has been associated with higher cardiovascular risk and is estimated to decrease the average life expectancy by as much as five years, because pre-hypertension often develops into hypertension (50% of people within 4 years) 5,6 .
Even then, high blood pressure (hypertension) is still largely ignored as a public health problem in most developing countries; because of the asymptomatic nature of the condition, most hypertensives are unaware they are affected 1,7 and so many people with hypertension do not seek the help of a doctor.Therefore, the detection and control of hypertension is a major public health challenge both developed and developing countries.
Various factors might have contributed to this rising trend, and, among the hypotheses, the consequences of urbanization, such as changes in life style patterns, diet, and stress and the overall epidemiologic transition, India is experiencing currently.As hypertension is one of the most important modifiable risk factors for cardiovascular disease, epidemiological studies to assess the prevalence of pre-hypertension and hypertension are urgently needed in developing countries like India to determine the baseline against which future trends in risk factor levels can be assessed and preventive strategies planned to promote health among all sections of the populations including reducing obesity, increasing physical activity, decreasing the extra salt intake of the population and a concerted effort to promote awareness about hypertension, its risk factors, and risk behaviours .
With these perspectives, this study was conducted to find out the prevalence of hypertension and pre-hypertension among adults 30 years and above with the covariates associated with hypertension among the adult population of rural and urban area of Puducherry, South India.

Settings and design:
A population based cross-sectional study was carried out in the field practice area of Department

Study period:
The study was conducted from 22 nd June 2009 to 31 st December 2009.

Sample size and sampling design:
With the available studies relating to prevalence of hypertension in India, the prevalence of 24.9 percent was taken for estimating the sample size requirement with limit of accuracy as 5 percent alpha error, 3 percent absolute allowable error, 15 percent for non-response and a design effect of 10 percent, accordingly the minimum sample size required for the study was found to be 1040 individuals 9 . All eligible individuals from selected area were identified from electoral roll of election commission of India, followed by preparation of two separate lists of eligible, one for urban area and another for rural area and there after 524 subjects from rural area and 516 subjects from urban area were selected by random sampling method.184 data (nonresponder / on treatment) were discarded and finally 856 data (410 data from rural area and 446 data from urban area) were analyzed.

Study instrument:
The data collection tool used for the study was an interview schedule that was developed at the Institute with the assistance from the faculty members and other experts.This pre-designed and pre-tested questionnaire contained questions relating to the information on family characteristics like residence, number of members in the family, family history of hypertension, and personal characteristics like age, sex, education, occupation, dietary habit, alcohol consumption and smoking habit.By initial translation, back-translation, re-translation followed by pilot study the questionnaire was custom-made for the study.The pilot study was carried out at the institute among general subjects following which some of the questions from the interview schedule were modified.Blood pressures as well as anthropometric measurements were taken.

Data collection procedure:
All the participants were explained about the purpose of the study and were ensured strict confidentiality.Informed consent was obtained from all the participants.Blood pressure measurement was done for each participant after half an hour of sitting in any calm area and due explanation to the examined participant about the objective of the study.The blood pressure was measured using the auscultatory method with a standardized calibrated mercury column type sphygmomanometer and an appropriate sized cuff encircling at least 80 percent of the arm in the seated posture, with feet on the floor and arm supported at heart level.Following a standardized protocol, they made two separate measurements and recorded the average of the two measurements after proper rest.In some cases, where high blood pressure was recorded for the first time, the physicians checked the blood pressure more than twice and took the average of the two close readings.Systolic BP is the point at which the first of 2 or more sounds is heard (phase I) and diastolic BP is the point before the disappearance of sounds (phase 5).Data regarding family and personal characteristics were recorded by personal interview.Body weight was measured (to the nearest 0.5 kg) in the standing motionless on the bath room scale with feet 15 cm apart, and weight equally distributed on each leg.Height was measured (to the nearest 0.5 cm) by stadeometer in standing position with closed feet, holding their breath in full inspiration and Frankfurt line of vision.Waist circumference was measured by flexible nonstretchable measuring tape in standing.A maximum of three visits were conducted for those who could not be contacted during the first visit.

Diagnostic criteria of undiagnosed Hypertension:
Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7), 2004 recommendation was used for diagnostic criteria for the diagnosis of hypertension ''Persons with the systolic blood pressure ≥ 140 mm of Hg and or diastolic blood pressure ≥ 90 mm of Hg and not on treatment were classified as undiagnosed case of hypertension'' 10 .

Diagnostic criteria of undiagnosed Prehypertension:
Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7), 2004 recommendation used for diagnostic criteria for the diagnosis of hypertension ''Persons with the systolic blood pressure ≥ 120 mm of Hg but <140 mm of Hg and or diastolic blood pressure ≥ 80 mm of Hg but <90 mm of Hg and not on treatment were classified as undiagnosed case of pre-hypertension'' 9 .

Diagnostic criteria of smoking:
Current smoker was defined as someone who at the time of study used to smoke either daily or occasionally.Nonsmokers were individuals who never smoked at all.

Diagnostic criteria of alcohol intake:
A "current drinker" was defined as one who consumed one or more drinks of any type of alcohol in the year preceding the study.

Statistical analysis used:
Data habit, alcohol and tobacco addiction, family history of hypertension, body mass index and waist circumference.In univariate analysis chi square test was employed for comparison, Odds ratio (OR) and 95 percent confidence interval (95% C.I.) of categorical variables.Backward LR method was used to perform binary logistic regressions, where presence of pre-hypertension and hypertension were used separately as dependent variable while others as independent variables.A two-tailed p value <0.05 was considered significant.

Results
Among 856 participants, 320 ( the differences was statistically significant.There were no significant sex difference of prevalence of pre-hypertension and hypertension.In the univariate analysis, probability of having increased risk of hypertension was significantly higher among adults with increasing age, having less than six members in the family, suffering from obesity (general and abdominal obesity) and living sedentary life, on the other hand probability of having increased risk of prehypertension was significantly higher among adults living in the rural areas, non-vegetarian dietary habit, obesity (general and abdominal obesity), sedentary lifestyle and family history of hypertension.   .This was similar to that reported from industrialized economies 19-21 .A study carried out among the Lepchas of Sikkim Himalayas has documented hypertension prevalence of 30.77 per cent among males and 25.77 per cent among females (By using older WHO criteria for hypertension) 22 .The most recent composite national data of the National Nutrition Monitoring Bureau of India has documented hypertension prevalence of 25 per cent among rural adults. [23]A study was among the Nicobarese aborigines during 2007 and 2009 noted a 50.5 percent prevalence 24 .

Age
In the current study, the prevalence of hypertension increased significantly with increasing age but prehypertension has not shown the same trend.Similar findings were reported by different researchers in various parts of India.In a north Indian study, they noted that hypertension was highest in the age group 60-69 years (64%) and prehypertension was highest (36%) in the group 30-39 years .

Sex
The prevalence of hypertension was not significantly different among males and females in this study.Others reported that hypertension was not associated with gender differences but significantly higher prevalence of prehypertension was noted in males 13,26 .We found comparable reports from other countries by Erem et al from Turkey 28 .The prevalence of hypertension being significantly higher in females than males were reported by Kanan et al, Prashant et al, Hazarika et al, Raina et al and Malhotra et al [14][15][16][17]30 .

Residence
In this study, magnitude of hypertension was not significantly different among urban area and rural area but pre-hypertension was significantly higher in rural peoples.However other studies have reported higher prevalence in urban areas than rural 31,32 .

Education
Educational status was not significantly associated with hypertension or pre-hypertension in this study.Educational status showed no association with hypertension in other studies conducted by Manimunda et al, Divan et al and others 24,25 .Erem et al reported from Turkey that lower education was associated with high prevalence of hypertension 28 .

Occupation
We noted that both hypertension and pre-hypertension was significantly associated with sedentary life style.Prevalence of hypertension was significantly more in people who lead a sedentary life style in the study of Yadav et  .

Diet
In the present study, magnitude of pre-hypertension was significantly more in non-vegetarians than vegetarians but the problem of hypertension was not associated with dietary habit.Reddy et al showed that prevalence of hypertension was more in non-vegetarians 26 .

Family size
Smaller family size (less than 6 members in the family) showed positive association with hypertension only in univariate analysis and not in multivariate logistic regression analysis 38 .On the contrary, Kannan et al reported that in rural Tamil Nadu, larger family size (more than 6 member) was significantly associated with high prevalence of hypertension 14 .

Family history of hypertension
Family history of hypertension was significantly associated with pre-hypertension only and not with hypertension in our study.Similar finding was reported by Yadav et al

Alcohol consumption
In the current study, neither hypertension nor prehypertension was found to have a significant association with alcohol consumption.No association with hypertension was however reported by Divan et al and Gupta et al 25,38 .Contrarily, KokiwarPrashant et al found a negative association between alcohol intake and hypertension 15 .Others studies have found alcohol consumption to be positively associated with hypertension 14,24,26,30 .

Smoking habit
In the present study, smoking habit was significantly associated with both hypertension and pre-hypertension. .

Body mass index (general obesity)
We noted that in the participants both hypertension and pre-hypertension were significantly associated with body mass index.Similar findings were reported by Yadav et

Central obesity
Central obesity was significantly associated with both hypertension and pre-hypertension in the present study.Similar findings were also reported by other researchers from different parts of India 13, 15, 27, 41 .In a Chennai study, the researchers noted differential risk factors in the analysis in hypertension and pre-hypertension.After the age and sex correction they identified obesity, diet, family history and middle-income group as correlating with pre-hypertension.On the other hand, the factors that predict hypertension were age, sex, smoking, alcohol intake, sedentary lifestyle, and type of work 34 .
The strength of the study was that it was a population based cross-sectional study to find the prevalence of undiagnosed hypertension among adults in both urban and rural areas.So far there has been no study reported in this field in the state and to the extent of our knowledge this was one of the recent studies reported from the South India.
Still there were several limitations that need to be addressed by further research.First, time and the quantity of information relayed to the participants may have rendered them less attentive to the evaluation procedure during interview although participants made no mention of this being a problem.Secondly, we did not evaluate the literacy skills of our participants, but simply evaluated formal education as a risk factor that may have a confounding effect in hypertension and prehypertension.Thirdly, we could not include in the study of the prevalence among adolescents and young adults.Finally, participants in this study were recruited from a corner of country.So they are unlikely to fully represent the diversity within the Indian community itself.This may have lead to a bias favouring the characteristics of the particular groups represented herein, thus limiting the external validity.

Future scope of study
Future interventions need to strive more to identify the precise genetic and environmental mechanisms underlying increased cardiovascular risk in Indian citizens.Clinical strategies must be developed that identify Indians at increased risk and assess the effectiveness of treatment for insulin resistance, and other cardiovascular risk factors, in this racial group 42 .

Clinical relevance
Our study suggests that there is a high prevalence of hypertension and pre-hypertension in the population of Puducherry in South India.We hope to find out ways that this study can be repeated at regular intervals in the adjacent areas of the state and in different states of our country by multicentre study to find out a nationally representative database.Our findings had the potential to address the awareness, prevention and intervention gap for hypertension in the high risk population.

What this study adds
It is a poignant time at present for patients at risk for developing hypertension that is per se a 'silent killer disease'.In our study we observed 27.6 percent hypertensive and 57 percent pre-hypertensive among our participants.Moreover, we noted that in the adults with the increasing age, rural residence, illiteracy, non-vegetarian diet, obesity (general and abdominal obesity), sedentary life and family history of hypertension are more likely hazardous factors for the hypertensive disorders.

Conclusion
Our findings could lay the foundation for the introduction of primary health care with community participation in combination with lifestyle modification for effective prevention of the cardiovascular diseases.The key factor to prevent hypertension is that we have to generate awareness among our peer groups, public health experts, health services researchers, healthcare providers and planners to consider the higher prevalence and associated risk factors of hypertension as a public health problem in India.

Conflict of Interests
There are no conflicts of interest among authors arising from the study.

13 .
But positive association of hypertension with family history was reported by Goldstein et al, Carretero et al, Divan et al, Reddy et al and Erem et al 25, 26,28, 39, 40 .

Table 3 : Correlates of systemic hypertension: Univariate Analysis
obesity (general and central).The above findings signify that there is likelihood of having increased risk of hypertension was higher among adults with these risk factors in the web of causation.

Table 4 : Correlates of systemic hypertension among adults: final model -Bivariate Logistic Regression (backward likelihood ratio method)
hypertension and 35.8 and 47.7 percent pre-hypertension in systolic and diastolic groups respectively in West Bengal, Yadav et al reported 32.2 percent hypertension and 32.3 percent pre-hypertension from Lucknow in the rural Central India, Kannan et al reported 25.2 percent hypertension from Tamil Nadu, Prashant R et al reported 19.04 percent hypertension and 18.8 percent pre-hypertension from rural central India 9, 13-15 .From eastern India, Hazarika et al reported a prevalence of 33.3 percent in the age group of 30 years and above among the native population of Assam in 30 years and above age group 16 .While hypertension was 13 percent in rural adults more than 30 years of age in Jammu, Chow et al reported 27 percent hypertension in rural adults > 30 years of Andhra Pradesh 9. While Das et al reported 24.9 percent of rural al, Kokiwar Prashant et al, Singh et al, Malhotra et al, Anand et al, Chockalingam et al and Zachariah et al Similar finding was reported by KokiwarPrashant et al, Malhotra et al, Kanan et al , Gupta et al, Reddy et al al, KokiwarPrashant et al, Raina et al, Kanan et al, Gupta et al, Manimunda et al,Reddy et al, Raheena et al, Singh et al, Beegom et al and Erem et al 13-15, 17, 24, 26-28, 38, 41 .