Clinical Resarch Artrcale
 

Prevalence of Coronary Heart Disease in the Urban Adult Males of
Eastern Nepal: A population-based analytical cross-sectional study

Abhinav Vaidya, paras Kumar Polkharel, s Nagesh, prahlad karki,
sanjay Kumar, shankhar Majhi
Department of Community Medicine, Kathmandu Medical College teaching Hospital, Kathmandu, Nepal
department of Community Medicine, Department of Internal Medicine, Department of Biochemistery,
B.P. Koirala Institute of Health Science, Dharan, Nepal

Abstract

Objective Despite being a rising public health problem, the burden of cardiovascular diseases (CVDs) at population level have not been studied in Nepal. The paper aims to bridge the gap and study the prevalence of coronary heart disease (CHD) and associated risk factors in adult males of urban Nepal.

Methods A population-based analytical cross-sectional study was carried out in the Dharan municipality of Nepal with one thousand males aged ≥ 35 years selected by systematic random sampling of the households. Data collection included WHO Rose angina questionnaire and electrocardiograms in all who had positive Rose Questionnaire. Those with documented CHD, positive Rose Questionnaire and positive electrocardiographic changes according to the Minnesota codes were labelled as having CHD.

Findings The prevalence of CHD in the study population was 5.7% (95% confidence interval: 4.26 – 7.13). The significant associated risk factors included tobacco use, history of hypertension, family history and age.

Conclusion This is the first population-based prevalence study of coronary heart disease in Nepal. The burden of CHD in the study population is comparable to the findings from urban studies of North India. Nepal urgently requires public health policies and programmes to address CVDs including CHD.

Keywords: prevalence, population-based, coronary heart disease, Dharan, Nepal.
INTRODUCTION

Cardiovascular disease (CVD) is the most prevalent yet one of the most preventable causes of death. Among the various types of cardiovascular diseases, coronary heart disease (CHD) is the largest cause of death, and ranks fifth in terms of disease burden.1 Whereas age-adjusted cardiovascular death rates have declined in several developed countries in past decades, rates of CVD have risen greatly in low-income and middle-income countries.2 In 1990, two-thirds of the 14 million cardiovascular fatalities worldwide occurred in the developing countries.3-5

Like other developing countries, Nepal is challenged by poverty, infectious and communicable diseases, high maternal deaths, malnutrition and lack of a competent health care system. While it has been struggling to combat the menace of communicable diseases, non-communicable diseases such as CVDs have remained largely neglected. So far Nepal far does not have a specific policy or programme regarding CVDs. Lack of proper surveillance system and appropriate policies have led to silent fostering of CVDs. To develop any kind of policy and programme, it is absolutely crucial that we first measure the burden of the problem. But very few studies have been done to deal with this rising public health problem and most of them are only hospital-based reports. Researches, if any, have been limited to certain risk factors such as hypertension or tobacco use. There is in fact not a single study reported regarding the prevalence of CHD at a community level. Hence, this research has been undertaken with the principal objective of obtaining a baseline data on prevalence of coronary heart disease and associated risk factors in urban Nepal.
DATA AND METHODS

Setting and participants
A population-based analytical cross-sectional study was undertaken in the Dharan municipality in 2005-6 with one thousand males aged ≥ 35 years. Dharan is one of the three municipalities in the Sunsari District of Koshi zone in the Eastern Nepal and can be considered a prototype of most of the towns in Nepal (fig.1). It has a total population of 116 491 according to the latest census of 2001. B.P. Koirala Institute of Health Sciences (BPKIHS) in Dharan is an important tertiary care that provides high quality health care service to the eastern region of Nepal and parts of northern India.

Fig.1: Location map of the Dharan Municipality, Nepal.
Correspondence: Dr. Abhinav Vaidya, MD,Lecturer, Department of Community Medicine, Kathmandu Medical College Teaching Hospital, Sinamangal, Kathmandu, Nepal
E mail: dr.abhinavaidya@gmail.com
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Sample size for the present study was calculated with the standard formula (4pq/L2) using a prevalence rate of 10% based on the studies from urban India. Sampling of the participants was done by systematic random sampling of the households with application of population proportionate to size technique.  The selected households were visited between June 2005 and February 2006. In case there was more than one male aged ≥ 35 years in a household, all the males aged ≥ 35 years in that household were enlisted and by lottery method, one of them was chosen as the respondent. An adjacent household was taken if there was no male aged ≥ 35 years in the household, if the eligible respondent was currently temporarily living away and was unlikely to return in the immediate future or could not be contacted even after three visits to the household or did not consent to participate in the study.

Tools of data collection
Questions were asked in Nepali language and recorded in English language by the principal investigator.  All the respondents were questioned about socio-demographic profile, dietary profile, physical activity, stress, tobacco and alcohol taking habits, etc. In addition, a section on WHO Rose angina questionnaire, which is a standardized and validated method6, 7 of measuring angina pectoris in general populations, was included to screen for angina in all except those with documented CHD. Physical examination included measurements for blood pressure, height, weight, waist and hip circumferences, and investigations included electrocardiograms in all who had positive Rose Questionnaire which was interpreted using the Minnesota Codes. The main operational definitions used in the study are presented in the table1.



Ethical approval
Ethical clearance was taken from the ethical committee of the institute (BPKIHS) and informed consent was obtained from the participants. Those with suspected coronary heart disease, any risk factor or any other disease, was appropriately advised either life-style modifications, treatment or referred to physicians or cardiologists.

Data analysis
The collected data was analysed with STATA 9.0. Chi-square test and Student’s t-test were applied to test the significance of differences among proportions and means respectively. Odds ratios with their 95% confidence intervals (95%CI) were calculated.

RESULTS
Respondents had been enquired if they had any documented history of chest pain suggestive of angina or infarction, previously diagnosed CHD including admission for a myocardial infarction or if they had undergone any coronary interventions. Twenty one of the respondents responded positively for this query, with 13 of them having history of myocardial infarction and another 8 suffering from unstable angina. Hence, the prevalence of definite CHD found in the study was 2.1% (fig.2). In the rest of the respondents who did not give a history of documented CHD (n=979), Rose questionnaire had been administered. Altogether 36 respondents responded positively to the questionnaire i.e. they had angina according to the given criteria. All of the 36 respondents with Rose angina had their resting electrocardiograms taken and interpreted, out of which ECGs of 24 respondents showed presence of electrographic changes suggestive of myocardial ischemia. These respondents with both Rose angina and ECG changes were termed ‘probable CHD’. The remainders (n=12) of the 36 respondents who had Rose angina but no suggestive ECG changes were termed ‘possible CHD’. Respondents with definite CHD, possible CHD and probable CHD were pooled together as “CHD positive” giving an overall CHD prevalence of 57/1000 (5.7%, 95%CI: 4.26 – 7.13). This combined value was used in the rest of the analysis. And the larger section of the population who had no documented history of CHD or Rose angina, were assumed to be ‘normal’ and classified as ‘CHD negative’. The association between the dependent variable (CHD) and the different independent variables was analysed and the results are presented in tables 2 & 3.

Fig.2: Flow chart illustrating the methodology of the study and the categorization of the population on the basis of CHD

 
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Prevalence of CHD in Urban Adult Males of Eastern Nepal
 

Table 1: Operational Definitions


Coronary heart disease 8

Definite CHD

 

Documented history of chest pain suggestive of angina or infarction and previously diagnosed CAD including self reported admission for a myocardial infarction, percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass surgery (CABG)

Probable CHD

Presence of both Rose angina and ECG suggestive of CHD as evidenced by the presence of electrographic changes namely Minnesota codes 1-1-1 through 1-1-7 or 1-2-1 through 1-2-7; presence of major ST-segment and major T-wave and Q-wave changes or Q-wave changes only in absence of high voltage R-wave (Minnesota codes 4-1-1 and 4-1-2 and 5-1 and 5-2).

Possible CHD

Affirmative response to Rose questionnaire after excluding any obvious cause of pain due to local factors. ECG not suggestive of CHD.

Normal

If the subject has none of the above findings.

Ethnicity 9

Major hill caste

Included Brahmins, Chhetris, Newars

Hill native

Included Rai, Limbu, Magar, Gurung

Hill occupational caste

Included Bishwokarmas, etc.

Terai caste

Included Yadavs, Musalmans, and Tharus.

Occupation

Agriculture

landlords, or into agro-related works

Ex-army

previously serving in the British or Indian army (Lahure)

Technical

Included those who do clerical works, office-goers, businessmen and shopkeepers

Labour

Included skilled and  unskilled labourers

Others

Students, politicians, priests, writers, artists, etc.

Socio-economic status

Low, middle and high

By Kutty’s scoring system10 by taking into account the educational status of the household, the land holding, the consumables owned and the type of house living in.

Physical activity11

Sedentary, light, moderate and heavy

By asking the activities during work, leisure and in household works assigning the highest score in each category that he merits. The final score to be reckoned as the highest in any category attributed to him.

Stress 11

Defined as feeling irritable or filled with anxiety: at home, work or if financial stress.

Never; sometimes;
Often; always

0 episode in a month; < 5 episodes in a month; > 5 episodes in  a month; > 5 episodes in a week

Tobacco use

Non users

If one has never smoked cigarettes, etc or chewed any form of tobacco

Current users

Currently smoking on a regular basis, one or more cigarettes, etc per day or currently using any form of tobacco.

Past users

Smoked cigarettes, etc or chewed any form of tobacco in the past but not currently. (Ex-smoker if previously smoking cigarettes.)

Passive smokers

Who do not use tobacco but are exposed to other’s smoke for a significant duration

Alcohol

Never; Occasional;
Frequent; past

Who has never taken alcohol;1-4 times a month; >once a week; those who have quit drinking completely

Hypertension

classified according to WHO/ISH 12 as:

Normotensive

Optimal: SBP of <120 and DBP of < 80; Normal:  SBP of <130 and DBP of < 85
High normal: SBP of 130-139 and DBP of 85-90

Hypertensive

Mild: SBP of 140-159 and DBP of 90-99; Moderate: SBP of 160-179 and DBP of 100-109; Severe: ≥180 and ≥ 110

BMI

categorized according to the WHO criteria: 13

Underweight;normal;
Overweight; obese

if BMI < 18.5 kg/m2 ;18.5 to 24.9 kg/m2; 25.0 to 29.9 kg/m2; ≥ 30.0 kg/m2
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Table 2: Comparison of the CHD positive and CHD negative population in terms of their socio-demographic characteristics

Characteristics

CHD positive

CHD negative

OR
(95% CI)

Adjusted OR
(95% CI)

Age (years)

 

 

 

 

35-49

9 (1.9)

466 (98.1)

Ref

Ref

50-64

20 (6.2)

305 (93.8)

3.39 ( 1.52-7.55)

1.97(0.79-  4.88)

≥ 65

28 (14.0)

172 (86.0)

8.43 (3.90-18.22)

2.73(0.98 -7.60)

Ethnicity

 

 

 

 

Terai caste

0(0.0)

23(100.0)

 

 

Major hill caste

33(6.8)

452(93.2)

Ref

Ref

Hill native caste

19(4.6)

397(95.4)

0.65 (0.36-1.17)

0.32 (0.07 - 1.37)

Hill occupational caste

5(6.6)

71(93.4)

0.96(0.36- 2.55)

0.90 (0.26 - 3.11)

Religion

 

 

 

 

Hinduism

35 (6.5)

503 (93.5)

Ref

Ref

Buddhism / Kirat

22 (5.0)

418 (95.0)

0.75(0.44- 1.31)

1.32 ( 0.33-5.20 )

Others

0 (0.0)

22 (100.0)

-

 

Marital Status

 

 

 

 

Single

3 (7.1)

39 (92.9)

Ref

Ref

Married

54 (5.6)

904 (94.4)

0.89(0.26- 3.03)

1.52 (0.38 -6.14)

Level of education

 

 

 

 

Illiterate

21 (8.8)

219 (91.3)

Ref

Ref

School education

30 (5.1)

562 (94.9)

0.55(0.31- 0.99)

0.53 (0.25 - 1.14)

Higher education

6 (3.6)

162 (96.4)

0.38(0.15- 0.97)

0.33 (0.08 - 1.34)

Current job status

 

 

 

 

Employed

21 (3.1)

650 (96.9)

Ref

Ref

Retired

36 (10.9)

293 (89.1)

3.79(2.17- 6.61)

2.37 (0.10- 5.62)

Occupation

 

 

 

 

Labour

6 (2.6)

227 (97.4)

Ref

Ref

Agriculture

18 (11.1)

144 (88.9)

4.73 (1.83- 12.19)

1.26(0.40 -4.00)

Ex-army

11 (8.3)

121 (91.7)

3.43 (1.24- 9.52)

1.08 (0.26 -4.40)

Technical

21 (5.1)

393 (94.9)

2.02 (0 .80- 5.08)

0.90 ( 0.27-3.02)

Others

1 (1.7)

58 (98.3)

0.65(0.07- 5.52)

0.25 (0.02- 2.70)

Socio-economic status

 

 

 

 

Low

20 (4.5)

428 (95.5)

Ref

Ref

Middle

34 (7.2)

436 (92.8)

1.66(0.94- 2.94)

1.71 (0.77-3.78)

High

3 (3.7)

79 (96.3)

0.81(0.23- 2.79)

1.08 (0.24-4.91)

Ref: Reference value

DISCUSSION
Prevalence of CHD

Our cross-sectional study on males aged ≥35 years in Dharan municipality for non-fatal CHD yielded a prevalence rate of 5.7% (95% CI: 4.26 – 7.13). There are no national studies to compare our results with and hence, most of the comparisons have been done with the Indian studies. In the 1990 Delhi study by Chaddha14, the prevalence of CHD by history was 3.95% in men which is very close to 3.6% in our study for Rose angina positives (table 4). Again, definite CHD prevalence at 2.1% is slightly higher than the 1.4% of the Kerala study by Kutty10; probably due to the rural set up, the inclusion of females and a lower cut-off of age at 25. The Jaipur
study by Gupta 15 included all the three criteria as our study and gave an overall prevalence of 6.0% in men which is very close to the 5.7% in our study. Hence, it can be presumed that the prevalence of CHD in our study closely compares with the prevalence rates from urban India.

The WHO (Rose) chest pain questionnaire
Unlike the CHD cases seen in the hospitals that generally present with the typical coronary symptoms, detection of CHD cases in a free-living community is a difficult task. The conventional methods include the tools such as Rose angina questionnaire, that rely on the history of chest pain, and, electrocardiography, both of which have got their own limitations. More specific techniques such as coronary angiography are invasive and hence impractical.

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Table 3: Comparison of the CHD positive and CHD negative population in terms of their life-style and anthropometric characteristics


Characteristics

CHD positive

CHD negative

OR
(95% CI)

Adjusted OR
(95% CI)

Dietary habit

 

 

 

 

Vegetarian

10 (9.4)

96 (90.6)

Ref

Ref

Non-vegetarian

47 (5.3)

847 (94.7)

0.52(0.24-  1.10)

0.61(0.24-1.51)

Physical activity

 

 

 

 

Sedentary

8 (10.3)

70 (89.7)

Ref

Ref

Light

31 (8.5)

332 (91.5)

0.82(0.36-1.85)

1.35 (0.51-3.56)

Moderate

13 (3.7)

334 (96.3)

0.34(0.13-0.85)

0.69 (0.24-2.05)

Heavy

5 (2.4)

207 (97.6)

0.21(0.06- 0.66)

0.72 (0.16-3.28)

Family history for CHD

 

 

 

 

Absent

52 (5.4)

917 (94.6)

Ref

Ref

Present

5 (16.1)

26 (83.9)

3.39 (1.25-9.19)

5.85 (1.53 -22.31)

Stress history

 

 

 

 

Never/rare

5 (2.6)

185 (97.4)

Ref

Ref

Sometimes

28 (4.8)

561 (95.2)

1.84 (0.70-4.85)

1.63 (0.59-4.53)

Often

18 (10.6)

152 (89.4)

4.38(1.59-12.07)

4.26 (1.39-13.10)

Always

6 (11.8)

45 (88.2)

4.93 (1.44-16.89)

3.46 (0.87-13.80)

Alcohol intake

 

 

 

 

Never

17 (5.8)

277 (94.2)

Ref

Ref

Occasional

3 (2.7)

110 (97.3)

0.44 (0.13-1.54)

0.77(0.19-3.06)

Frequent

16 (3.9)

391 (96.1)

0.67 (0.33-1.34)

1.17 (0.49-2.80)

Previously drinking

21 (11.3)

165 (88.7)

2.07(1.06-4.04)

1.89(0.77-4.64)

Tobacco intake

 

 

 

 

Never

16 (3.1)

494 (96.9)

Ref

Ref

Current

19 (7.3)

241(92.7)

2.43 (1.23-4.82)

1.75 (0.79-3.89)

Past

22 (9.6)

208 (90.4)

3.27 (1.68- 6.34)

2.96 (1.30-6.76)

Blood pressure

 

 

 

 

Normotensive

9 (4.6)

187 (95.4)

Ref

Ref

Pre-Hypertensive

28 (4.8)

549 (95.2)

1.06(0.49-2.29)

0.83 (0.34-1.99)

Hypertensive, stage 1

9 (6.5)

129 (93.5)

1.45(0.56-3.75)

1.15 (0.39-3.43)

Hypertensive, stage 2

11 (12.4)

78 (87.6)

2.93( 1.17-7.35)

2.00 (0.68-5.87)

Body Mass Index

 

 

 

 

Underweight

1 (4.0)

24 (96.0)

Ref

Ref

Normal

32 (5.6)

542 (94.4)

1.41( 0.18-10.8)

0.98(0.10-8.99)

Overweight

21 (6.38)

308 (93.6)

1.64 ( 0.21-12.69)

1.15 (0.12-11.00)

Obese

3 (4.17)

69 (95.83)

1.04 ( 0.10-10.52)

0.75 (0.06-9.75)

Waist Hip Ratio

 

 

 

 

Normal

25 (5.1)

463 (94.9)

Ref

Ref

High

32 (6.3)

480 (93.8)

1.23(0.72-2.11)

1.09 (0.57-2.07)

Ref: Reference value

Table 4: Comparison of the findings of this study with selected studies from India*


First author

Year

Place

Urban
/rural

Age
Group
(yrs)

Sample
size

Overall prevalence

Diagnosis by history (men)

Diagnosis by ECG (men)

Definite
CHD

Mathur 16

1960

Agra

Urban

NA

1046

1.05

 

 

 

Padmavati 17

1962

Delhi

Urban

NA

1642

1.04

 

 

 

Chaddha 14

1990

Delhi

Urban

25-64

13723

9.67

3.95

5.63

 

Kutty 10

1993

Kerala

Rural

>25

1130

7.43

 

 

1.4

Gupta 15

1995

Jaipur

Urban

>20

2212

6

 

3.5

 

This study

2004-5

Dharan,
Nepal

Urban

≥35

1000

5.7

3.6

2.4

2.1

* Adapted from Gupta et al. South Asian J preventive cardiology 1997; 1: 27-32. NA: information not available     

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Abhinav Vaidya et al
 

The Rose questionnaire is a screening tool originally designed for use in men and has consistently been shown to be predictive of major ischaemic heart disease events particularly in the middle aged men. For example, in a population-based prospective study18 on 7735 randomly selected men, who were administered questionnaire at baseline and followed-up for first major ischaemic heart disease event, the relative risks (95% CI) of a major ischaemic heart disease event were 2.03 (1.61, 2.57) for angina compared to no chest pain. Similarly, the association between Rose questionnaire angina pectoris and coronary calcification investigated in  the Rotterdam Coronary Calcification Study19 found the presence angina pectoris was strongly associated with a 12.9-fold (95% CI: 3.8-43.7) increased risk of a calcium score >1000.

Reports have shown the questionnaire to be more specific in males than in females. For example, Garber CE et al20 compared "Rose Questionnaire Angina" to exercise thallium scintigraphy and found that though the sensitivity of the Questionnaire was similar in females (41%) and males (44%), the specificity was significantly lower in females than  in males (56% vs 77%). However, the performance of the Rose angina questionnaire has been sufficiently inconsistent to warrant a more objective diagnostic method to verify it, particularly to achieve greater cross-cultural validity.

Coronary risk factors
Premature CHD, defined as CHD before the age of 55 years in men, was found to be prevalent in 2.3% of the study population who were aged 55 years or less. The mean age of CHD positive respondents in our study was 64.65±12.65 years, marginally higher compared to 62.5±9.8 years in a Moradabad study21. Likewise, in the Jaipur Heart watch-2 study15, CAD was more prevalent as the age advanced (10.25% in 40-49 years, 19% in 50-59 years and 23.45% in >60 years). The corresponding figures for our study were 9%, 11% and 37%. The prevalence of CHD in the youngest age group 20-29 years of the Jaipur study was even higher (3.3%) than that in our youngest age-group which was 35-49 years. So it is likely that the CHD is not very prevalent in the younger age group in our context in contrast to the scenario in India where more and more young adults are being affected with CHD.

Employment and CHD have been associated in many studies. In our study, the retired had CHD more than the employed (10.9% vs. 3.1%) which was highly significant statistically (p< 0.001). But the association did not remain significant (p=0.129) after adjusting for age confirming the effect of age as a confounder in the association between employment and CHD.

Physical activity was significantly associated with CHD in our study (p=0.002) with increasing prevalence of CHD seen in those who were not physically active. After age-adjustment, however, the association was no longer significant as the elder people were significantly less physically active than the youngsters. Similarly, CHD was more common in those who reported to have more stress in their lives (p=0.002) than those who did not. The odd of having CHD was 4 times more in those who reported to have rare episodes of stress in comparison to those who were always stressed. Other studies have also found up to 3-fold increased risk of CHD in men.22-24 However, reports25  also have shown that people who perceive and report their life to be most stressful also tend to over-report symptoms of CHD thus leading to a spurious exposure-outcome association. In our study also, 7.8% & 6.5% of those who were often (>5 episodes a month) or always (>5 times a week) stressed reported positively to Rose angina questionnaire in contrary to 2.0% and 1.1% in those who reported stress to be occurring sometimes (<5times a week) or rarely.

Family history was strongly and significantly associated with CHD in our study. After adjusting for age and other risk factors, the probability of having CHD was more than 5 times higher in those who had a positive family history of premature CHD in comparison to those who did not have. Our findings are similar to advanced studies which have found a relative odds of 1.93 (1.25-3) in a prospective study26 & OR of 2.18 in a case-control study.27

In our study, past users of tobacco had a greater prevalence of CHD (9.6%) than the current users (3.1%) or the non-users (7.3%). After adjusting for age and other factors, in comparison to non-users, the current users had less than two times more and the past users had almost three times more probability of having CHD. In the cross-sectional study from Jaipur, the RR for CHD of tobacco use of all forms was 1.49 for rural and 1.33 for urban men.28 Similarly, the Banglore hospital case-control study29 had given ORs of 3.2 for cigarettes alone, 4.0 for beedis alone and 5.3 for cigarettes and beedis combined. Thus, like in other studies, tobacco consumption appears to be a crucial factor in the development of CHD in this population also. Even passive smoking seems to be an important factor for having CHD as they were 6 times more likely to have CHD in comparison to those who were not exposed which is quite high than the overall RR of 1.25 obtained by a meta-analysis of 10 prospective cohort studies and 8 case-control studies.30

 
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Prevalence of CHD in Urban Adult Males of Eastern Nepal
 
CONCLUSION

This is the first population-based prevalence study of coronary heart disease in Nepal and the burden of CHD in this population seems to follow the trend of India. Among the international studies on coronary heart disease in which Nepal had participted, Interheart11 is a recent, large, international, standardized, case-control study and the most important risk factors according to the study were smoking, hypertension, diabetes, abdominal obesity, psychological factors, consumption of fruits, vegetables, and alcohol, and  physical inactivity. On the other hand, the important factors associated with CHD in our study included tobacco use, age, history of hypertension and family history. It is very likely that diabetes and dyslipidemia are also vital risk factors in this study population but as they had not been thoroughly explored, not much can be commented upon regarding their significance in the study population. Nevertheless, it is quite likely that the factors found in the Interheart study are important to this study population too. The bottomline is that Public health policies and programmes to address CVDs including CHD and the associated risk factors are urgently required in Nepal.

COMPETING INTERESTS: None.

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