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Prevalence of coronary artery disease and its risk factors in Kerala, South India: a community-based cross-sectional study

  • M. N. Krishnan1,
  • G. Zachariah2,
  • K. Venugopal3,
  • P. P. Mohanan4,
  • S. Harikrishnan5,
  • G. Sanjay5,
  • L. Jeyaseelan6 and
  • K. R. Thankappan7Email author
BMC Cardiovascular Disorders201616:12

https://doi.org/10.1186/s12872-016-0189-3

Received: 25 September 2015

Accepted: 8 January 2016

Published: 14 January 2016

Abstract

Background

There are no recent data on prevalence of coronary artery disease (CAD) in Indians. The last community based study from Kerala, the most advanced Indian state in epidemiological transition, was in 1993 that reported 1.4 % definite CAD prevalence. We studied the prevalence of CAD and its risk factors among adults in Kerala.

Methods

In a community-based cross sectional study, we selected 5167 adults (mean age 51 years, men 40.1 %) using a multistage cluster sampling method. Information on socio-demographics, smoking, alcohol use, physical activity, dietary habits and personal history of hypertension, diabetes, and CAD was collected using a structured interview schedule. Anthropometry, blood pressure, electrocardiogram, and biochemical investigations were done using standard protocols. CAD and its risk factors were defined using standard criteria. Comparisons of age adjusted prevalence were done using two tailed proportion tests.

Results

The overall age-adjusted prevalence of definite CAD was 3.5 %: men 4.8 %, women 2.6 % (p < 0.001). Prevalence of any CAD was 12.5 %: men 9.8 %, women 14.3 % (p < 0.001). There was no difference in definite CAD between urban and rural population. Physical inactivity was reported by 17.5 and 18 % reported family history of CAD. Other CAD risk factors detected in the study were: overweight or obese 59 %, abdominal obesity 57 %, hypertension 28 %, diabetes 15 %, high total cholesterol 52 % and low level of high density lipoprotein cholesterol 39 %. Current smoking was reported only be men (28 %).

Conclusion

The prevalence of definite CAD in Kerala increased nearly three times since 1993 without any difference in urban and rural areas. Most risk factors of CAD were highly prevalent in the state. Both population and individual level approaches are warranted to address the high level of CAD risk factors to reduce the increasing prevalence of CAD in this population.

Keywords

Coronary artery disease Coronary risk factors Prevalence Kerala India

Background

Coronary artery disease (CAD) is the foremost cause of disability and death the world over and is one of the top five causes of death in Indian population [1]. Mortality from CAD in Indians is predicted to increase rapidly and overtake that of the high-income countries. Among adults over 20 years of age, there has been a two-fold rise in CAD in rural areas and a 6-fold rise in urban areas during the period from 1960 to 2002 [2]. Previous studies have shown high prevalence of CAD in Asian Indians residing in the United States [3]. However there are no robust and contemporary data on CAD in native Indians. In a systematic review of CAD prevalence from India, Ahmed et al. commented that none of the studies conformed to the requirements of a high-quality epidemiologic study [4]. Kerala, with a population of over 33 million, is the most advanced state in epidemiological transition and has the highest prevalence of CAD risk factors in India [5]. The state has been reported to be the harbinger of what the rest of India is going to face in the near future [5]. The INTERHEART study reported the importance of conventional risk factors associated with CAD [6]. Although the CAD risk factor prevalence is the highest in the state of Kerala, there are no recent studies on the prevalence of CAD in this state. The only one community based study in 1993 from the rural area of the southernmost district of the state reported a CAD prevalence of 7.4 % [7]. The environment in Kerala is conducive for increasing the CAD risk factors [8] which is likely to result in an increase in the CAD prevalence. Therefore we wanted to study the current prevalence of CAD and its major risk factors in Kerala.

Methods

A detailed description of the design, sample, and methods of the study has already been published [9]. Briefly, this was a cross-sectional community-based study during the period from January to June 2011. We estimated the sample size based on an anticipated prevalence of 7.4 % of CAD for rural Kerala based on the data by Kutty et al. [7] and 11 % for urban Kerala based on the study by Mohan et al. in Chennai [10]. The total sample size was estimated to be 3000 in rural and 2400 in urban areas. Sample selection procedure is given in Fig. 1. Subjects aged 20–79 years were selected using a multistage cluster sampling procedure. In the first stage three out of the 14 districts of Kerala state were selected. The 14 districts were grouped into five northern, five southern and four central districts. From the northern group of districts, Kozhikode district was selected which included the city corporation of Kozhikode. In the southern group of districts, Thiruvananthapuram and Kollam districts had city corporations. Of these Thiruvananthapuram was selected randomly. In the central group of districts there were two districts which included corporations; Ernakulam and Thrissur. Of these Thrissur district was selected randomly. In the second stage, one ward was randomly selected from each of the three city corporation wards in the urban area. Each of the selected wards was divided into six geographic regions. One of these geographic regions was selected randomly as the study area. All the households in this area were eligible to be included in this sample. One subject between 20 and 59 years was selected using KISH method [11] and all the subjects between 60 and 79 years were included.
Fig. 1

Sample selection procedure

In rural area, two of the Panchayats from the above three districts were randomly selected. From each of these Panchayats, one ward was randomly selected. All the households in the selected ward were eligible to be included on the sample. One subject between the age of 20 and 59 years was selected using KISH method and all subjects between 60 and 79 years were included.

Each selected individual was invited to visit an easily accessible facility with all past medical records after overnight fasting. Trained investigators collected all the relevant data.

Using a structured interview schedule, information on basic socio-economic and demographic details, smoking, physical activity, dietary habits, personal history of hypertension, dyslipidemia, diabetes mellitus and CAD were collected. The instrument also contained the Rose Angina Questionnaire (RAQ) [12, 13] and questions related to history of documented prior myocardial infarction, unstable angina, coronary artery bypass grafting (CABG) surgery, noninvasive investigations for CAD, coronary angiography, coronary angioplasty, documented use of drugs for CAD and hospital admission for CAD. Family history of ischemic heart disease, stroke and coronary risk factors was also recorded.

Anthropometric measurements

Height was measured by wall-mounted stadiometer (Model 206, Seca, Hamburg Germany) to the nearest centimeter. Subjects were asked to stand upright without shoes, with their back against the wall, heels together and eyes directed forward.

Weight was measured with a portable electronic weighing scale (Model HN 283, Omron Corporation, Shimogyo-ku, Kyoto, Japan) kept on a firm horizontal surface. The subjects were asked to wear light clothing and remove footwear. Weight was recorded in kilograms to the nearest 0.5Kg. Body mass index was calculated as weight in kg/(height in meter squared) [14].

Waist circumference was measured using a non-stretchable measuring tape. The subjects were asked to stand erect in a relaxed position with both feet together. Waist girth was measured at the midpoint between the iliac crest and the lower margin of the ribs at the end of expiration, to the nearest centimeter.

Blood pressure

Blood pressure was recorded with electronic apparatus (model 1A2, Omron Corporation, Shimogyo-ku, Kyoto, Japan) in sitting position, on the left arm resting on a table at heart level, after the subject having rested for at least 15 min. Three readings were taken 3 min apart and the mean of the last two readings was recorded as the BP. Heart rate was also recorded.

Electrocardiogram

Resting 12 lead electrocardiogram (ECG) was performed on all subjects by trained technicians with three-channel digital ECG recorders with facility for display and measured parameters. For each lead, five consecutive complexes were recorded. Minnesota coding [15] and application of CAD criteria were performed by an experienced cardiologist for the respective region; those subjects diagnosed to have CAD were re-evaluated by another cardiologist in a blinded manner. Disagreements were resolved by consensus. Similar procedure was followed for 10 % of randomly selected subjects without a diagnosis of CAD.

Biochemical investigations

Blood samples were drawn from individuals after 10–12 h of fasting. Plasma glucose was estimated immediately, onsite using the Glucose oxidase/ peroxidase- phenol-4-amenophenazone method (GOD-PAP). Blood samples for lipid profile measurement were transported on ice packs (4–6 °C) to an accredited core laboratory (Thyrocare Technologies Ltd, Navi Mumbai, India) on the same day. Estimation was carried out within 48 h in clinical chemistry instruments (Olympus AU2700) and Advia 1800 chemistry system (Siemens) using standard commercially available kits (Agappe Diagnostics). Photometry technology was used for lipid profile. Serum cholesterol was measured by cholesterol oxidase phenol 4- aminoantipyrine peroxidase (CHOD-PAP) method and serum triglycerides by glycerol-3 -phosphate oxidase -p - aminophenzone peroxidase (GPO-PAP) method. High density lipoprotein (HDL) cholesterol was estimated by enzyme selective protection method. The reaction between cholesterol assays is suppressed by the electrostatic interaction between polyanions & cationic substances. Low-density lipoprotein (LDL) cholesterol was calculated by using Friedwald’s equation.

Ethical clearance

The present study was in compliance with the Helsinki Declaration. The study was approved by the Ethics Committee of Cardiological Society of India, Kerala Chapter. Informed written consent was obtained from all participants.

Definitions used

We defined coronary artery disease as: (a) Definite CAD based on any of: documented evidence of prior acute coronary syndrome (ACS) or treatment for CAD, documented history of undergoing coronary angioplasty or CABG, more than 50 % epicardial coronary stenosis by invasive coronary angiography, ECG showing pathological Q waves (any of Minnesota code 1-1-1 to 1-1-7 or 1-2-1 to 1-2-5 or 1-2-7), imaging evidence of a region of loss of viable myocardium that is thinned and has a motion abnormality, in the absence of a non-ischemic cause [16], RAQ angina plus ECG changes (any of Minnesota codes 4-1-1, 4-1-2, 4-2 or 5-l, 5-2), or RAQ angina plus positive treadmill ECG (exercise-induced horizontal or down-sloping ST depression of ≥ 1 mm at 80 ms from J point), or inducible ischemia on stress imaging;(b) Probable CAD based on any of (in the absence of any of the definite criteria): RAQ angina without significant ECG changes, ECG changes (any of Minnesota Code 4-1-1,4-1-2, 4-2 or 5-1, 5-2) without RAQ angina, or positive treadmill ECG without RAQ angina. Any CAD was defined as those who satisfied either definite or probable CAD criteria.

We defined diabetes mellitus as fasting blood glucose value of ≥ 7 mmol/L and/or if there was current use of medications for diabetes [17], hypertension as blood pressure ≥140 mm of Hg systolic and/or ≥90 mm of Hg diastolic and/or currently on drugs for high blood pressure [18], and dyslipidemia as any of: serum total cholesterol ≥ 5.18 mmol/L, serum LDL cholesterol ≥ 3.37 mmol/L, serum HDL cholesterol <1.04 mmol/L in men or < 1.29 mmol/L in women, or serum triglycerides ≥1.69 mmol /L [19]. We categorized body mass index (BMI) as normal (18.0–22.9 kg/m2), overweight (23.0–24.9 kg/m2), or obesity (≥25 kg/m2). Abdominal obesity was defined as a waist circumference of ≥90 cm in men or ≥80 cm in women [20]. Physical activity levels were classified into sedentary and non-sedentary. All subjects reporting physical activity for at least 30 min a day for a minimum of 5 days a week (household activities involving physical effort, walking to and from work involving at least 30 min., manual workers, those performing leisure-time physical activity) were considered non-sedentary. All others were classified as sedentary [21]. We determined the socioeconomic status of the participants using the validated standard of living Index tool developed by National Family Health Survey [22]. We divided our entire sample into tertiles, based upon the index score. Participants in the upper tertile were classified as high socioeconomic group, those in the middle tertile as intermediate socioeconomic group and lower tertile as low socioeconomic group.

Statistical analysis

We entered data into CS Pro software (the US Census Bureau) version 4 · 0 for Windows. Data cleaning and statistical analysis were performed using Stata (Stata Corp, Texas, USA) version 13 · 0 for Windows. All proportions were age-adjusted using WHO population data. Frequency distribution was done for categorical variables. Comparisons of age-adjusted prevalence between different categories were done using two-tailed proportion test. The difference in the age-adjusted prevalence and its 95 % confidence intervals are provided. P value <0 · 05 defined the level of statistical significance.

Results

Of the total 6477 individuals contacted, we could evaluate 5167 (men 40.1 %); overall response rate was 79.8 % (men 75.0 %, women 83.3 %). There were no missing data in the interview schedule, ECG or anthropometrics. Data on blood sugar and serum cholesterol were missing in 32 and 47 subjects respectively; these were excluded from analysis.

Table 1 depicts the demographic and behavioural characteristics of the participants by area. There were greater proportion of participants without formal education in rural area as compared to urban; those with >10 years of education were more in urban as compared to rural area. The proportion of subjects that reported current smoking was similar in rural and urban men. There was larger proportion of vegetarianism, obesity and abdominal obesity among urban participants.
Table 1

Baseline demographic and behavioural characteristics of the participants by area

Variable

 

Urban

Rural

Total

 

(N = 2248)

(N = 2919)

(N = 5167)

n

(%)

n

(%)

n

(%)

P value

Age

        
 

20–29

111

4.94

225

7.71

336

6.50

<0.001

30–39

345

15.35

543

18.60

888

17.19

 

40–49

507

22.55

692

23.71

1199

23.20

 

50–59

493

21.93

531

18.19

1024

19.82

 

60–69

566

25.18

650

22.27

1216

23.53

 

70–79

226

10.05

278

9.52

504

9.75

 

Sex

        
 

Men

971

43.19

1101

37.72

2072

40.10

<0.001

Women

1277

56.81

1818

62.28

3095

59.90

 

Socio-economic status

        
 

Low

630

28.02

1303

44.64

1933

37.41

<0.001

Middle

792

35.23

743

25.45

1535

29.71

 

High

826

36.74

873

29.91

1699

32.88

 

Educational status

        
 

No formal education

87

3.87

203

6.95

290

5.61

<0.001

1–4 years

208

9.25

437

14.97

645

12.48

 

5–10 years

1294

57.56

1729

59.23

3023

58.51

 

>10 years

659

29.31

550

18.84

1209

23.40

 

Smokinga

        
 

Never

523

55.52

443

44.04

966

49.59

<0.001

Past

111

11.78

220

21.87

331

16.99

 

Current

308

32.70

343

34.10

651

33.42

 

Physical activity

        
 

Sedentary

1770

78.74

2328

79.75

4098

79.31

0.371

Non-sedentary

478

21.26

591

20.25

1069

20.69

 

Dietary habits

        
 

Vegetarian

161

7.16

110

3.77

271

5.24

<0.001

Non-vegetarian

2087

92.84

2809

96.23

4896

94.76

 

BMI

        
 

Low

111

4.95

244

8.37

355

6.88

<0.001

Normal

685

30.53

1042

35.76

1727

33.48

 

Overweight

450

20.05

527

18.09

977

18.94

 

Obese

998

44.47

1101

37.78

2099

40.69

 

Abdominal Obesity

        
 

Yes

1394

62.20

1709

58.67

3103

60.21

<0.001

No

847

37.80

1204

41.33

2051

39.79

 

a Smoking in men only

Prevalence of coronary artery disease

The crude and age-adjusted prevalence of definite CAD in Kerala was 5.8 and 3.5 % respectively. The figures for men were 8.0 % and 4.8 % and for women 4.2 and 2.6 % respectively; the differences were significant across gender (p < 0.001). The overall crude and age-adjusted prevalence of any CAD in Kerala was 16.6 and 12.5 % respectively. The crude and age-adjusted prevalence of any CAD in men were 14.6 and 9.8 % and in women were 17.9 and 14.3 % respectively; the prevalence was significantly higher in women as compared to men (p < 0.001). Table 2 outlines the prevalence of CAD (any & definite) among different age groups and gender. As age increased, the prevalence of CAD increased in both gender.
Table 2

Crude and age-adjusted prevalence of CAD by age group and gender

Age group (yrs.)

Men

Women

Difference (%)

95 % CI

p value

Any CAD

n

P (%)

SE

n

P (%)

SE

20–29

144

2.78

1.37

192

7.29

1.88

−4.51

(−9.07,0.04)

0.069

30–39

306

6.54

1.42

582

8.93

1.18

−2.40

(−6.01,1.21)

0.213

40–49

465

7.10

1.19

734

14.44

1.30

−7.34

(−10.80,−3.89)

<0.001

50–59

386

12.44

1.68

638

19.91

1.58

−7.47

(−11.99,−2.95)

0.002

60–69

537

22.72

1.81

679

25.77

1.68

−3.05

(−7.89,1.78)

0.218

70–79

234

32.05

3.06

270

29.26

2.77

2.79

(−5.28,10.87)

0.497

All

2072

14.58

0.78

3095

17.87

0.69

−3.29

(−5.32,−1.26)

0.002

Age adjusted

2072

9.80

0.65

3095

14.26

0.69

−4.46

(−6.24,−2.69)

<0.001

Definite CAD

         

20–29

144

0.00

0.00

192

0.00

0.00

-

-

-

30–39

306

2.29

0.86

582

0.52

0.30

1.77

(0.00,3.55)

0.017

40–49

465

3.87

0.90

734

1.77

0.49

2.10

(0.10,4.10)

0.026

50–59

386

6.48

1.25

638

3.13

0.69

3.34

(0.54,6.14)

0.012

60–69

537

13.41

1.47

679

8.98

1.10

4.42

(0.83,8.02)

0.014

70–79

234

18.80

2.56

270

12.59

2.02

6.21

(−0.17,12.59)

0.055

All

2072

8.01

0.60

3095

4.23

0.36

3.78

(2.41,5.15)

<0.001

Age adjusted

2072

4.80

0.39

3095

2.63

0.23

2.17

(1.09,3.25)

<0.001

CAD coronary artery disease, P prevalence, SE standard error

The prevalence of definite CAD was similar irrespective of region or religion. The prevalence of any CAD was lowest among Christians and highest among Muslims (10 vs.15.8 % p = 0 · 002). Of the three geographical regions of Kerala, Thirvananthapuram had lower prevalence of any CAD compared to Thrissur and Kozhikode (8.3 vs. 14.4 and 14.7 % p < 0.001).

Table 3 depicts the age-adjusted prevalence of CAD (any and definite) by gender, age group (age ≤ 45 and >45 years), and by area. Age-adjusted prevalence of any CAD in participants ≤45 years and >45 years was 7.8 and 18.7 % respectively. Similarly the age-adjusted prevalence of definite CAD was 0.9 % in participants ≤45 years and 6.8 % in >45 years. Age-adjusted prevalence of CAD (any and definite) was significantly higher in participants >45 years (p < 0.001). The prevalence of any CAD was significantly higher in rural women (15.6 %) as compared to urban women (11.7 %) (p < 0.01). The overall prevalence of any CAD was higher in rural (13.2 %) than urban (11 · 3 %) area (p = 0.038). However, there was no difference between urban and rural areas in the overall prevalence of definite CAD (3.4 vs. 3.6 %) (p = 0.72).
Table 3

Age-adjusted prevalence of CAD by gender, age, and area

 

Gender

=/<45 years

>45 years

Difference (%)

95 % CI

p value

n

P (%)

SE

n

P (%)

SE

Any CAD

Men

728

5.12

0.82

1344

15.05

1.04

−9.92

(−12.42,−7.43)

<0.001

 

Women

1239

9.48

0.92

1856

21.08

1.10

−11.60

(−14.07,−9.13)

<0.001

 

All

1967

7.78

0.64

3200

18.68

0.78

−10.90

(−12.69,−9.10)

<0.001

Definite CAD

Men

728

1.82

0.43

1344

8.43

0.80

−6.61

(−8.39,−4.84)

<0.001

 

Women

1239

0.36

0.15

1856

5.61

0.58

−5.25

(−6.35,−4.15)

<0.001

 

All

1967

0.89

0.18

3200

6.80

0.47

−5.91

(−6.88,−4.95)

<0.001

  

Urban

Rural

   

Any CAD

Men

971

10.82

1.06

1101

8.94

0.81

1.88

(−0.70,4.46)

0.151

 

Women

1277

11.66

0.88

1818

15.63

0.94

−3.97

(−6.40,−1.55)

0.002

 

All

2248

11.31

0.68

2919

13.23

0.66

−1.92

(−3.72,−0.12)

0.038

Definite CAD

Men

971

4.92

0.57

1101

4.69

0.54

0.23

(−1.62,2.08)

0.806

 

Women

1277

2.24

0.29

1818

2.84

0.33

−0.60

(−1.72,0.51)

0.299

 

All

2248

3.38

0.29

2919

3.57

0.28

−0.18

(−1.19,0.82)

0.722

CAD coronary artery disease, P prevalence, SE standard error

Table 4 shows the age-adjusted prevalence of various criteria for diagnosis of CAD. ST code, T code, and RAQ angina were significantly higher in women; all other criteria were higher in men (p < 0.01). Table 5 represents the age-adjusted prevalence of various criteria for diagnosis of CAD among participants with any CAD. Again, most of the definite criteria for CAD were higher in men. Except ST code, T code, and RAQ angina, there was higher prevalence of various coronary artery criteria among men as compared to women (p < 0.001); ST code was higher in women, while T code and RAQ angina showed no significant difference. Among participants diagnosed to have any CAD, the prevalence of known CAD was 7.8 and 2.7 % in men and women respectively. Symptomatic CAD (sum of those with known CAD and RAQ angina) was prevalent in 54 % with any CAD.
Table 4

Age-adjusted prevalence of various CAD parameters among the total participant population

 

Total

Men

Women

Difference (%)

95 % CI

p value

n = 5167

n = 2072

n = 3095

P (%)

SE

P (%)

SE

P (%)

SE

Q codes

0.87

0.11

1.65

0.24

0.32

0.08

1.33

(0.74,1.91)

<0.001

ST Code

1.87

0.19

1.00

0.18

2.46

0.29

−1.47

(−2.16,−0.77)

<0.001

T code

5.46

0.35

3.86

0.46

6.44

0.49

−2.59

(−3.79,−1.39)

<0.001

Documented ACS

1.59

0.14

2.70

0.30

0.84

0.13

1.86

(1.09,2.63)

<0.001

Documented treatment for CAD

2.26

0.16

3.55

0.34

1.39

0.16

2.17

(1.27,3.07)

<0.001

Angioplasty/CABG or Fibrinolysis

0.44

0.07

0.96

0.17

0.05

0.03

0.91

(0.48,1.34)

<0.001

Angiographic Coronary stenosis

0.63

0.09

1.15

0.19

0.27

0.07

0.88

(0.39,1.37)

<0.001

Imaging evidence of RWMA

0.06

0.09

1.34

0.20

0.10

0.05

1.24

(0.73,1.74)

<0.001

RAQ angina

6.38

0.35

4.71

0.44

7.47

0.51

−2.76

(−4.06,−1.46)

<0.001

Positive treadmill ECG

0.54

0.08

0.98

0.17

0.22

0.07

0.76

(0.30,1.21)

<0.001

Table 5

Age-adjusted prevalence of various CAD parameters among any CAD

 

Total

Men

Women

Difference (%)

95 % CI

p value

n = 855

n = 302

n = 553

P (%)

SE

P (%)

SE

P (%)

SE

Q codes

4.88

0.79

12.22

2.48

1.49

0.40

10.74

(6.91,14.57)

<0.001

ST Code

12.94

2.16

7.08

1.51

15.14

2.74

−8.07

(−12.23,−3.91)

<0.001

T code

43.06

3.44

45.84

6.35

42.61

3.92

3.23

(−3.74,10.20)

0.3625

Documented ACS

8.68

0.98

20.36

2.85

3.80

0.71

16.56

(11.75,21.37)

<0.001

Documented treatment for CAD

11.88

1.05

26.56

2.95

5.98

0.79

20.59

(15.23,25.94)

<0.001

Angioplasty/CABG or Fibrinolysis

2.18

0.41

6.63

1.44

0.19

0.11

6.43

(3.60,9.26)

<0.001

Angiographic Coronary stenosis

3.21

0.55

8.07

1.81

1.10

0.31

6.98

(3.78,10.17)

<0.001

Imaging evidence of RWMA

3.03

0.46

8.75

1.56

0.40

0.19

8.34

(5.11,11.57)

<0.001

RAQ angina

49.69

3.44

43.98

6.43

51.60

3.96

−7.62

(−14.60,−0.64)

0.033

Positive treadmill ECG

2.74

0.52

6.26

1.33

1.12

0.51

5.14

(2.27,8.01)

<0.001

Q code-any of the Minnesota Q code 1-1-1 to 1-1-7 or 1-2-1 to 1-2-5 or 1-2-7; ST code-any of the Minnesota ST code 4-1-1,4-1-2 or 4–2; T code -any of the Minnesota T code 5-1 or 5-2; ACS acute coronary syndrome, CABG coronary artery bypass graft surgery, RWMA regional wall motion abnormality, ECG electrocardiogram, P prevalence, SE standard error

Coronary risk factors

Age-adjusted prevalence of major risk factors of CAD by gender and area is presented in Table 6. Conventional risk factors like diabetes mellitus, hypertension, high serum cholesterol, low serum HDL cholesterol, smoking, physical inactivity, and family history of CAD were highly prevalent in the state. Except low HDL cholesterol (23.9 % in urban men vs. 27.6 % in rural men), all other major risk factors were higher in urban men as compared to rural men. This pattern was also observed in urban women as compared to rural women except high serum cholesterol (49.2 vs. 52.4 %; p = 0.089) and low HDL cholesterol (43.4 vs. 48.7 %; p =0.004).
Table 6

Age adjusted prevalence of major risk factors of CAD by gender and area

Risk factor

All

Men

Women

p value**

  

Urban

Rural

p value*

Urban

Rural

p value*

 
 

n

%

SE

n

%

SE

n

%

SE

 

n

%

SE

n

%

SE

  

Diabetes

5135

15.23

0.50

962

19.14

1.40

1097

16.23

1.16

0.0831

1272

15.40

0.95

1804

12.47

0.73

0.020

<0.001

Hypertension

5153

28.44

0.63

967

39.99

2.04

1095

26.24

1.33

<0.001

1275

30.15

1.29

1816

23.42

0.85

<0.001

<0.001

High cholesterol

5121

52.31

0.88

960

56.54

2.22

1092

53.36

1.85

0.1487

1264

49.23

1.76

1805

52.35

1.35

0.089

0.023

Low HDL

5120

38.55

0.88

959

23.92

1.94

1092

27.56

1.69

0.0603

1264

43.41

2.02

1805

48.73

1.44

0.004

<0.001

Smoking

2072

28.05

1.19

971

30.45

2.00

1101

26.88

1.48

0.0721

-

-

-

-

-

-

-

-

Physical inactivity

5167

17.45

0.64

971

30.72

2.06

1101

28.77

1.64

0.3315

1277

11.19

1.19

1818

9.38

0.64

0.101

<0.001

Family history

5167

18.35

0.64

971

18.97

1.47

1101

17.37

1.39

0.3467

1277

20.37

1.39

1818

16.92

1.02

0.015

0.939

P prevalence, SE standard error, *p value between urban and rural; **p value between men and women

Risk factor analysis of any and definite CAD is presented in Table 7. The age adjusted prevalence of risk factors such as hypertension, low HDL and family history were significantly higher in any CAD group (p value <0.01). However, higher cholesterol and smoking were higher in no CAD group. In definite CAD, all risk factors except low HDL were statistically significant (p value <0.01). In addition, excluding higher cholesterol all age adjusted prevalence of these conventional risk factors was higher in definite CAD as compared to no CAD.
Table 7

Risk factors analysis of any and definite CAD

Risk factor

Any CAD

Definite CAD

 

Yes

No

Difference (%)

95 % CI

p value

Yes

No

Difference (%)

95 % CI

p value

 

n

%

SE

n

%

SE

   

n

%

SE

n

%

SE

   

Diabetes

851

17.07

1.97

4284

14.89

0.52

2.18

(−0.56,4.93)

0.106

296

33.30

5.24

4839

14.73

0.50

18.57

(13.11,24.03)

<0.001

Hypertension

852

32.19

2.04

4301

27.67

0.67

4.51

(1.10,7.92)

0.008

295

51.32

5.34

4858

28.04

0.64

23.29

(17.44,29.13)

<0.001

High cholesterol

849

47.63

3.24

4272

52.82

0.92

−5.19

(−8.86,−1.51)

0.006

293

41.01

5.68

4828

53.01

0.88

−12.00

(−17.81,−6.20)

<0.001

Low HDL

849

43.62

3.53

4271

37.59

0.92

6.04

(2.40,9.68)

0.001

293

42.76

5.90

4827

38.33

0.89

4.44

(−1.39,10.26)

0.13

Smoking

855

6.91

1.02

4312

11.80

0.56

−4.89

(−6.85,−2.94)

<0.001

297

15.69

4.42

4870

11.22

0.53

4.46

(0.23,8.69)

0.019

Physical inactivity

855

15.55

2.17

4312

17.49

0.68

−1.94

(−4.62,0.74)

0.170

297

31.02

5.32

4870

17.13

0.65

13.89

(8.52,19.25)

<0.001

Family history

855

27.06

3.09

4312

17.37

0.66

9.70

(6.51,12.88)

<0.001

297

25.29

4.06

4870

18.03

0.65

7.27

(2.21,12.33)

0.002

Discussion

Prevalence of coronary artery disease

Coronary artery disease has been gaining importance as a major public health problem in India. In 2003, the prevalence of CAD was estimated to be 3–4 % in rural areas and 8–10 % in urban areas according to a population-based cross sectional survey [23]. Our study also showed high prevalence of CAD in Kerala. The age-adjusted overall prevalence of definite CAD was 3.5 % and any CAD was 12.5 %. We chose criteria for any CAD to detect all possible cases of CAD; for definite CAD we have avoided less specific criteria like RAQ angina, positive treadmill electrocardiogram or minor electrocardiographic changes in isolation and used combined criteria when these less specific components were incorporated.

Age-adjusted prevalence of definite CAD was higher in men. However, any CAD prevalence in women was significantly higher than in men. It is well known that women commonly have ECG with nonspecific ST –T changes and angina with normal coronary arteries; this may have resulted in overestimation of any CAD prevalence in women. In our study the prevalence of RAQ angina and ST-T changes were significantly higher among women whose proportion in rural area (62 %) was higher than that of urban area (57 %). Earlier population studies also consistently recorded much higher prevalence of CAD in women using RAQ angina and ST-T criteria for diagnosis of CAD [2427]. It has also been noted that RAQ angina is less reliable in women [28] and non-white population [29]. Moreover, Patel et al. in a study from migrant South Asians observed that the value of ST-T changes alone as indicator of CAD was questionable, especially in women [30].

This study showed no difference in the prevalence of definite CAD between urban and rural population of Kerala while any CAD was slightly more in the rural population. Previous studies from other parts of India have highlighted the marked urban preponderance of CAD [25, 31, 32]. Some of the risk factors such as general obesity and abdominal obesity were higher in urban areas, whereas smoking was higher in rural area. There was no difference in physical inactivity in rural and urban areas. In most other Indian states there are huge differences between urban and rural areas. However, in Kerala these differences are either minimal or some risk factors are higher in urban while others are higher in rural as noted above. This could be the reason for not having significant difference of definite CAD prevalence in urban and rural areas of Kerala.

The overall age-adjusted prevalence of any CAD in subjects at or below the age of 45 years was 7.8 %. Our study showed a higher prevalence of CAD among young subjects compared to a previous study [7]; in this 1993 study, there were no subjects with definite CAD below the age of 45 years where as we found definite CAD in 0.9 %. It is well known that coronary artery disease occurs in Indians 5–10 years earlier [33, 34]. The average age of first myocardial infarction in Asians is 53 years; among the three Asian populations, Chinese, Malay, and Indian, the highest age-adjusted incidence of coronary events in both sexes was in Indians [6]. The age-adjusted prevalence of CAD in young subjects in our study was similar to the US data on prevalence of CAD in the young (1.2 %).

Comparisons with previous Indian studies on CAD prevalence may be problematic due to heterogeneity in period of study, sample characteristics, and criteria for diagnosis of CAD. We did a systematic search for articles in PubMed and EMBASE published during the period from 1990 to 2014 in English language on the prevalence of CAD in India by community-based surveys. We chose only studies that had a minimum sample size of 1000, and that based the diagnosis on documented history of CAD and ECG criteria. We could collect 11original articles, one systematic review [4] and one meta-analysis [35]. The studies were heterogeneous in terms of sampling methods, subject groups, and criteria for diagnosis. Most of the studies were from northern India. Only one study mentioned the period of field survey [25]. Only one study analyzed the data for definite CAD and probable CAD separately [7]. Most studies were on either rural or urban population; only four covered both the groups [25, 31, 32, 36]. Sample size calculations were reported in three studies [7, 25, 31]. In a study from Delhi during the period from 1984 to 1987, Chadda et al. reported unadjusted prevalence of 9.7 % in urban and 2.7 % in rural inhabitants [25]. The sample consisted of men and women aged 24–64 years; they used clinical history of CAD and electrocardiographic criteria for diagnosis of CAD. Gupta et al. published an epidemiological survey of urban inhabitants over 20 years of age in Rajasthan, India [27]. The prevalence of CAD was 7.6 % (6 % in men and 10.4 % in women). The age distribution of the sample was consistent with that of the population. Singh et al. in 1997 surveyed an urban and rural sample of 3575 subjects between the ages 25 and 64 years from North India and reported CAD prevalence of 9 and 3.3 % respectively [31]. Mohan and colleagues reported 9 % age-adjusted prevalence of CAD in an urban sample of Chennai, South India [10]. More recently, another study from India noted 12.6 % crude CAD prevalence in an urban population [37]. All these studies had used less specific criteria for diagnosis of CAD; definite CAD as we had analyzed had not been computed in these studies. A study from Pakistan showed a crude prevalence of definite CAD in 6.1 men and 4 % women; they found ischemic ECG changes much more prevalent in women [38].

The US statistics reported 6 % age-adjusted CAD prevalence in respondents above 18 years by survey based on self-reported CAD by telephonic interview [39]. The prevalence between ages 18–44 years was 1.2 %. The update on heart disease and stroke in the US reported CAD prevalence of 6.4%in adults ≥ 20 years of age. The prevalence of CAD was 7.9 for men and 5.1 % for women [40]. The higher figure in the US data may be due to differences in age, sample, survey methods, and criteria for diagnosis. The reported prevalence of CAD in the United Kingdom was 3.5 % [41]; this figure was similar to our data on definite CAD.

As to the figures for definite CAD, only one study [7] reported the prevalence (1.4 %); they found no participant below the age of 45 years with definite CAD. However, it should be noted that the age range in this study was 25–64 years and the population was rural only. Compared to this, our data show an increase in the prevalence of definite CAD (0.9 %). Any CAD prevalence of 11.3 % in urban and 13.2 % in rural area respectively in our study was higher compared to some previous studies in the same age group and similar definition for CAD (8.1–9 % for urban and 3.5–5 % for rural) [10, 27, 42, 43]. These data indicate an increase in the prevalence of any CAD over the past two decades. The increase in prevalence of any CAD may partially be due to improvement of treatment of CAD thus allowing better survival.

The urban prevalence data in this study may be comparable to other cities of India; however, the rural figures for prevalence may not be comparable to most rural areas in rest of India since rural Kerala is different from rest of rural India in social and economic development.

Prevalence of coronary risk factors

We found high prevalence of major conventional risk factors for CAD in our survey. The prevalence of various risk factors in our study like diabetes (15.2 %), hypertension (28.4 %), high cholesterol (52.3 %) and smoking in men (28.1 %) was comparable to the figures in a recent large study from Kerala, by Thankappan et al. [5]. The figures were also similar in the US adult population [44]. Physical activity in our study seems to be an overestimate due to the problems of self reports as has been reported by a recent study from Kerala [45].

Limitations of the study

Our study was the largest and most comprehensive contemporary community-based survey on the prevalence of CAD and its risk factors from India. The geographic spread of the survey enabled us to derive meaningful inferences of prevalence from the state. We could capture all the necessary data from participants with very little missing variables. One of the limitations for our study was the sub-optimal response rate, which could reach only ~ 80 %; the response rate was lower in rural men. We could not capture the reasons for the poor response in men although we surmise that, being manual laborers many of them would be working on Sundays. As a result the sample consisted of higher proportion of women than in the general population. Sex disaggregated data will partly take care of this problem. There was significantly higher proportion of older individuals compared to the population of Kerala although age-adjustment in analysis would have removed this bias.

Conclusion

Our study revealed a high age-adjusted prevalence of CAD and coronary risk factors in Kerala, South India. Our study did not show any difference in the CAD prevalence in urban and rural population. Our data on prevalence of CAD are comparable to the figures from the US and the United Kingdom. Compared to previous Indian studies and the 1993 study of Kerala, this study showed higher prevalence of CAD in Kerala. The prevalence of definite CAD in Kerala increased nearly three times since 1993 without any difference in urban and rural areas. Most risk factors of CAD were highly prevalent in the state. Both population and individual level approaches are warranted to address the high level of CAD risk factors to reduce the increasing prevalence of CAD in this population.

Abbreviations

ACS: 

acute coronary syndrome

CHOD-PAP: 

cholesterol oxidase phenol 4-aminoantipyrine peroxidase

CABG: 

coronary artery bypass grafting

CAD: 

coronary artery disease

ECG: 

electrocardiogram

GOD-PAP: 

glucose oxidase/ peroxidase-phenol-4-amenophenazone method

HDL: 

high density lipoprotein

LDL): 

low-density lipoprotein

RAQ: 

rose angina questionnaire

Declarations

Acknowledgements

We thankfully acknowledge the Cardiological Society of India Kerala Chapter for the generous and exclusive funding of the study. We also appreciate the important intellectual input provided by Dr. Mark Huffman.

Dedication

For the Cardiological Society of India Kerala Chapter Coronary Artery Disease and Risk Factors Prevalence (CSI Kerala-CRP) Study Investigators.

Funding

The study was funded exclusively by the Cardiological Society of India, Kerala Chapter; this is the professional organization of cardiologists in this region. The funding source had no role in the design, data collection, analysis or interpretation or writing up of the article.

Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Authors’ Affiliations

(1)
Govt. Medical College
(2)
Mother Hospital
(3)
Pushpagiri Hospital
(4)
Westfort High-tech Hospital
(5)
Sree Chitra Tirunal Institute for Medical Sciences and Technology
(6)
Department of Biostatistics, Christian Medical College
(7)
Achutha Menon Centre for Health Science Studies, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum Medical College

References

  1. Gupta R, Guptha S, Sharma KK, Gupta A, Deedwania P. Regional variations in cardiovascular risk factors in India: India Heart Watch. World J Cardiol. 2012;4:112–20.PubMedPubMed CentralView ArticleGoogle Scholar
  2. Gupta R, Joshi P, Mohan V, Reddy KS, Yusuf S. Epidemiology and causation of coronary heart disease and stroke in India. Heart. 2008;94:16–26.PubMedView ArticleGoogle Scholar
  3. Enas EA, Garg A, Davidson MA, Nair VM, Huet BA, Yusuf S. Coronary heart disease and its risk factors in first-generation immigrant Asian Indians to the United States of America. Indian Heart J. 1996;48:343–53.PubMedGoogle Scholar
  4. Ahmed N, Bhopal R. Is coronary heart disease rising in India? A systematic review based on ECG defined coronary heart disease. Heart. 2005;91:719–25.View ArticleGoogle Scholar
  5. Thankappan KR, Shah B, Mathur P, Sarma PS, Srinivas G, Mini GK, et al. Risk factor profile for chronic non-communicable diseases: results of a community-based study in Kerala, India. Indian J Med Res. 2010;131:53–63.PubMedGoogle Scholar
  6. Yusuf S, Hawken S, Ounpuu S, Dans T, Avezum A, Lanas F, et al. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study. Lancet. 2004;364:937–52.PubMedView ArticleGoogle Scholar
  7. Kutty VR, Balakrishnan KG, Jayasree AK, Thomas J. Prevalence of coronary heart disease in the rural population of Thiruvananthapuram district, Kerala, India. Int J Cardiol. 1993;39:59–70.PubMedView ArticleGoogle Scholar
  8. Sivasankaran S, Thankappan KR. Prevention of non-communicable diseases requires a life course approach: a case study from Kerala. Indian J Med Res. 2013;137:874–7.PubMedPubMed CentralGoogle Scholar
  9. Zachariah G, Harikrishnan S, Krishnan MN, Mohanan PP, Sanjay G, Venugopal K, et al. Prevalence of coronary artery disease and coronary risk factors in Kerala, South India: a population survey-design and methods. Indian Heart J. 2013;65:243–9.PubMedPubMed CentralView ArticleGoogle Scholar
  10. Mohan V, Deepa R, Rani SS, Premalatha G. Prevalence of coronary artery disease and its relationship to lipids in a selected population in South India: The Chennai Urban Population Study (CUPS No. 5). J Am Coll Cardiol. 2001;38:682–7.PubMedView ArticleGoogle Scholar
  11. World Health Organization. WHO STEPS Manual, WHO STEPS Surveillance, Part 2: Planning and Set Up; Section 2: Preparing the sample. 2008. p. 2-2-24–25.Google Scholar
  12. Rose GA. The diagnosis of ischemic heart pain and intermittent claudication in field surveys. Bull World Health Organ. 1962;27:645–58.PubMedPubMed CentralGoogle Scholar
  13. Rose GA, Blackburn H. Cardiovascular survey methods. Monogr Ser World Health Organ. 1968;56:1–188.PubMedGoogle Scholar
  14. World Health Organization. WHO STEPS Part 3, Training and practical Guides. Section 3: Guide to physical measurements (Step 2). 2008. p. 3-3-1–3-3-14.Google Scholar
  15. Ronald JP, Richards SC, Zhu-Ming Z. The Minnesota Code manual of electrocardiographic findings. Second edition Springer. 2010.Google Scholar
  16. Mendis S, Thygesen K, Kuulasmaa K, Giampaoli S, Mähönen M, Ngu Blackett K, et al. World Health Organization definition of myocardial infarction:2008–09 revision. Int J Epidemiol. 2011;40:139–46.PubMedView ArticleGoogle Scholar
  17. American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes Care. 2010;33(1):S62–9.PubMed CentralView ArticleGoogle Scholar
  18. Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo Jr JL, et al. The Seventh report of the Joint National Committee on prevention, detection, evaluation, and treatment of high blood pressure: The JNC 7 Report. JAMA. 2003;289:2560–72.PubMedView ArticleGoogle Scholar
  19. Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults, Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Executive Summary of The Third Report of The National Cholesterol Education Program (NCEP) Expert Panel on detection, evaluation, and treatment of high blood cholesterol in Adults (Adult Treatment Panel III). JAMA. 2001;285:2486–97.View ArticleGoogle Scholar
  20. Misra A, Chowbey P, Makkar BM, Vikram NK, Wasir JS, Chadha D, et al. Consensus Statement for diagnosis of obesity, abdominal obesity and the metabolic syndrome for Asian Indians and recommendations for physical activity, medical and surgical management. J Assoc Physicians India. 2009;57:163–70.PubMedGoogle Scholar
  21. World Health Organization. Global recommendations on physical activity for health. Geneva: World Health Organization; 2010. http://www.whqlibdoc.who.int/ publications/2010/9789241599979_eng.pdf. Accessed 5 Dec 2015.Google Scholar
  22. International Institute of Population Sciences (IIPS), ORC Macro. National family health survey (NFHS −2), India, 1998–99. Mumbai: International Institute of Population Sciences; 2000.Google Scholar
  23. Gupta R. Burden of coronary heart disease in India. Indian Heart J. 2005;57:632–8.PubMedGoogle Scholar
  24. Sarvotham SG, Berry JN. Prevalence of coronary heart disease in an urban population in northern India. Circulation. 1968;37:939–53.PubMedView ArticleGoogle Scholar
  25. Chadha SL, Radhakrishnan S, Ramachandran K, Kaul U, Gopinath N. Epidemiological study of coronary heart disease in urban population of Delhi. Indian J Med Res. 1990;92:424–30.PubMedGoogle Scholar
  26. Gupta R, Prakash H, Majumdar S, Sharma SC, Gupta VP. Prevalence of coronary heart disease and coronary risk factors in an urban population of Rajasthan. Indian Heart J. 1995;47:331–8.PubMedGoogle Scholar
  27. Gupta R, Gupta VP, Sarna M, Bhatnagar S, Thanvi J, Sharma V, et al. Prevalence of coronary heart disease and risk factors in an urban Indian population: Jaipur Heart Watch-2. Indian Heart J. 2002;54:59–66.PubMedGoogle Scholar
  28. Harris RB, Weissfeld LA. Gender differences in the reliability of reporting symptoms of angina pectoris. J Clin Epidemiol. 1991;44:1071–8.PubMedView ArticleGoogle Scholar
  29. Fischbacher CM, Bhopal R, Unwin N, White M, Alberti KG. The performance of the Rose angina questionnaire in South Asian and European origin populations: a comparative study in Newcastle. UK Int J Epidemiol. 2001;30:1009–16.PubMedView ArticleGoogle Scholar
  30. Patel DJ, Winterbotham M, Sutherland SE, Britt RG, Keil JE, Sutton GC. Comparison of methods to assess coronary heart disease prevalence in South Asians. Natl Med J India. 1997;10:210–3.PubMedGoogle Scholar
  31. Singh RB, Sharma JP, Rastogi V, Raghuvanshi RS, Moshiri M, Verma SP, et al. Prevalence of coronary artery disease and coronary risk factors in rural and urban populations of north India. Eur Heart J. 1997;18:1728–35.PubMedView ArticleGoogle Scholar
  32. Kumar R, Singh MC, Singh MC, Ahlawat SK, Thakur JS, Srivastava A, et al. Urbanization and coronary heart disease: a study of urban–rural differences in northern India. Indian Heart J. 2006;58:126–30.PubMedGoogle Scholar
  33. Hughes LO, Raval U, Raftery EB. First myocardial infarctions in Asian and white men. BMJ. 1989;298:1345–50.PubMedPubMed CentralView ArticleGoogle Scholar
  34. Enas EA, Dhawan J, Petkar S. Coronary artery disease in Asian Indians: lessons learnt and the role of lipoprotein(a). Indian Heart J. 1997;49:25–34.PubMedGoogle Scholar
  35. Gupta R, Gupta VP. Meta-analysis of coronary heart disease prevalence in India. Indian Heart J. 1996;48:241–5.PubMedGoogle Scholar
  36. Kamili M, Dar I, Ali G, Wazir H, Hussain S. Prevalence of coronary heart disease in Kashmiris. Indian Heart J. 2007;59:44–9.PubMedGoogle Scholar
  37. Latheef SA, Subramanyam G. Prevalence of coronary artery disease and coronary risk factors in an urban population of Tirupati. Indian Heart J. 2007;59:157–64.PubMedGoogle Scholar
  38. Jafar TH, Qadri Z, Chaturvedi N. Coronary artery disease epidemic in Pakistan: more electrocardiographic evidence of ischemia in women than in men. Heart. 2008;94:408–13.PubMedPubMed CentralView ArticleGoogle Scholar
  39. Centers for Disease Control and Prevention (CDC). Prevalence of coronary heart disease --United States, 2006–2010. MMWR Morb Mortal Wkly Rep. 2011;60:1377–81.Google Scholar
  40. Go AS, Mozaffarian D, Roger VL, Benjamin EJ, Berry JD, Blaha MJ, et al. Executive summary: heart disease and stroke statistics--2014 update: a report from the American Heart Association. Circulation. 2014;129:399–410.PubMedView ArticleGoogle Scholar
  41. Townsend N, Wickramasinghe K, Bhatnagar P. Coronary heart disease statistics. London: British Heart Foundation; 2012. p. 82.Google Scholar
  42. Gupta R, Gupta HP, Keswani P, Sharma S, Gupta VP, Gupta KD. Coronary heart disease and coronary risk factors in rural Rajasthan. J Assoc Physicians India. 1994;42:24–6.PubMedGoogle Scholar
  43. Gupta AK, Bharadwaj A, Ashotra S, Gupta BP. Feasibility and training of multipurpose workers in detection, prevention and control of coronary artery disease in apple-belt of Shimla hills. South Asian J Prev Cardiol. 2002;6:17–22.Google Scholar
  44. Go AS, Mozaffarian D, Roger VL, Benjamin EJ, Berry JD, Blaha MJ, et al. Heart disease and stroke statistics-2014 update: a report from the American heart association. Circulation. 2014;129:e28–292. doi:10.1161/01.cir.0000441139.02102.80.PubMedView ArticleGoogle Scholar
  45. Mathews E, Pratt M, Jissa VT, Thankappan KR. Self-reported physical activity and its correlates among adult women in the expanded part of Thiruvananthapuram City, India. Indian J Public Health. 2015;59:136–40.PubMedView ArticleGoogle Scholar

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© Krishnan et al. 2016

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