Abstract

With improvements in life expectancy and as more and more people have access to modern medicine, ooncommunicable diseases are emerging as a health problem in both urban and nval communities in Myanmar. O f all non-communicable diseases, cardiovascular diseases (CVD) are known to be the major health problem. Since many studies that have been conducted in bothdeveloped and developing countries have shown a difference between rural and urban communities with regard to cardiovascular diseases, our study had the objective of finding out the prevalena? of ischemic heart disease, hypertensive heart disease and rheumatic heart disease in a rural and urban community. The risk of obesity and smoking in the occurrence of CVD was also studied. A cross-sectional s w e y was conducted in three urban townships of Yangon City (Sanchaung, Latha and Pabedan) and one rural township of Hmawbi. The results showed that CVDwerea healthprobleminboth the urban and rural communities. Coronary heart disease was seen to be more prevalent in the urban townships than in the rural Hmawbi Township, but hypertension (HT) and rheumatic heart diseases (RHD) were more prevalent in the ruraltownshipof Hmawbi. Obesity which has been blamed as the major risk factor for C H D and HT in the developed countries w a s not found to be a risk factor in the study townships, but smoking was. Asia Pac J P u b l i c IIcalth 1992/1993;6(4): 188-94. Keywords: Cardiovascular diseases, coronary heart disease, hypertension, Myanmar, obesity, rheumatic heart diseases, smoking.

Address for reprints: Dr Aung, Professor and Consultant Cardiologist, Cardiovascular Diwasc Project Manager, Yangon General Hospital.

Prevalence of Cardiovascular Diseases in Rural Area of Hmawbi and Urban Yangon City Aung*, MBBS, FRCP

Myo Thct Htoon**, M R R S , MPH Thcin Ngwet, hlRBS, M P H Nyan Tun*, MBBS, MPI-I May Mon K y a d , MRBS

* Yangon General Hospital ** Health ServicesResearch, Department of Health +Preventiveand Social Medicine Department, Institute of Medicine I, Yangon Preventive and Social Medicine Department, Institute of Medicine, Mandalay *CVDControl Project, Department of Health

*

Introduction Health issues in Myanmar have always centered on communicable diseases but, during the past decade, with improvements in life expectancy, and as more and more people have access to modern medicine, noncommunicable diseases have come to be seen as an emerging health problem in both urban and rural communities in Myanmar. Cardiovascular diseases (CVD) are a leading cause of mohality and morbidity in industrial countries and they are also emerging as a public health problem in the developing countries'. Of all the noncommunicable diseases, cardiovascular diseases have been known to be the major health problem. The spectrum of cardiovascular diseases is very wide, ranging from rheumatic fever occurring in children to ischemic heart disease and hypertension occurring in the much older age groups. Apart from the lack ofeasily available preventive measures, information on the magnitude of CVD has also been incomplete. Most of the available data on CVD are hospital based and therefore naturally do not represent the true picture in the country. Future plans for drawing up cardiovascular disease prevention and control programs, along with the allocation of scant resources, depends on

the reliable base line data. Manystudies that wereconducted in both developed and developing countries have shown a difference between rural and urban c o m m u n i t i e ~with ~ * ~ regard to cardiovascular diseases. This study was conducted with the objective of findingout the prevalenceofischemic heart disease, hypertensive heart disease and rheumatic heart disease in niral and urban communities. The risk of obesity and smoking in the occurrence of CVD was also studied.

Met hods A cross-sectional survey was con-

ducted in three urban townships of Yangon City and one rural township of Hmawbi. The three urban townships, namely Sanchaung, Latha and Pabedan, were chosen as the study area because these townships were assumed to be representativeofthe popu1ationofYangonCity.The totalpopulation in Sanchaung, Latha and Pabedan was 89,000, 120,000 and 110,000 respectively. In each of the selected townships, three wards were randomly selected. In each of these selected wards, every tenth household was visited and all household members over the age of 15 years were selected as study subjects. Hmawbi Township was selected as the study area for the rural population because

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Asia-Pacific Journal ofPublic Health 1992/1993 Vol. 6 No. 4

it isa typical ruralcommunity. It hasa total population of 105,000. For rural Hmawbi Township, three villages were randomly selected and all the household members over the age of 15 years living in these selected villages were included as subjects in the study. A total of 1,195 individuals were examined in the three urban communities out of a total of 1,758 eligible subjects. In the three rural villages, a total of 1,4 I6 were examined out of a total eligible population of 1,875. In both the rural and urban surveys there were no subjects who refused to participate in the study and those that were not included in the studywere thosewho were away from home at the time of the survey. Interviewers used in the study were physicians who had been trained especially for this survey by the principal investigator. All subjects were first screened for cardiovascular diseases by a senior physician trained in cardiology. The diagnosis was then re-confirmed by the Professor of cardiology from the Yangon General Hospital. Pre-test of the survey interview schedule was conducted in Lamadnw township. The end points for coronary heart disease were determined by standard epidemiological methods4*' and consisted ofangina pectorisgrade I and grade I1 according to Rose Criteria, possible myocardial infarction (major Q wave), or history of myocardial infarction or severe chest pain for more than halfan hour, and ischemic resting electrocardiographic abnormalities. Blood pressure was measured using a standard mercury sphygmoma-

nometer after the participant had been seated for at least five minutes. Blood pressure was taken in a sitting position with a single reading6. The cut-off point for hypertension was 160/95 mm Hg'. Rheumatic heart disease diagnosis was based on the modified Jones Criteria' and the type of valvular lesion and characteristic clinical findings supported by other investigations including echo~ardiography'*'~.The cut-off point for normality of body mass index was taken as 20 as recommended by the WHO study group on diet, nutrition a n d prevention of chronic diseases'

'.

Findings Asshown inTable 1 , theprevalenceof coronary heart disease (CHD) was 13.38 per 1000 population (950/0 CI 6.88 to 19.89) in the urban areas, and in the rural areas it was found to be 8.47 per 1000population (95%CI 3.7 to 13.24).CHDwasseentobeslightly higher in the urban areas with the standardized prevalence rate of 12.03 per 1000. The prevalenceofhypertension (HT) was 57.9 1 per 1000 popula-

tion (95% CI 45.75 to 70.07) and the corresponding figure for the urban area was 42.68 per 1000 population (95% CI 31.22 to 54.14). The standardized prevalence rate for the urban areas was 4 9 per 1000 population which is observed to be much lower than that for the rural areas. Rheumatic heart disease (RHD) was also observed to be much higher in the rural areas. In the urban areas, the prevalence of RHD was seen to be 5.86 per 1000 population (95% CI 1.59 to 10.19) compared to 19.07 per 1000 population (95% CI 11.99 to 26.19) in the rural areas. In both theurbanand ruralareas, the prevalence ofCHD was seen to be high in males compared to females in all age groups (Tables 2 and 3). The highest prevalence of CHD was seen in the45 to 54 yearsage group for both sexes combined in the urban area, whereas for the rural area the peak prevalence was observed in the 6 5 years and above age group. The age-standardized prevalence rate of CHD for the urban population was 12.03 per 1000 population which was higher than that of the rural prevalence.

Table 1. Prcvalencc of coronary heart disease, hypertcnsion and rheumatic hcart discasc in rural and urban populations (per 1000 pop.) of agc 15 ycars and above

Disease Coronary heart disease Hypertension Rheumatic heart disease

Urban

Rural

13.38 (95%CI 6.88 to 19.89) 42.68 (95%CI 31.22 to54.14) 5.86 (95%CI 1.59to 10.19)

8.47 (95%CI 3.7 to 13.24) 57.9 1 (95%CI45.75 to70.07) 19.07 (95%CI 11.99to26.19)

Tablc 2. Age and scs distribution of the prevalenceof coronary hcart disease in urban (per 1000 population)

PREVALENCE Age (yrs) 15-24 25-34 35-44 45-54 55-64 65 &above ~~

TOTAL

Male

CHD Female

-

-

-

111

-

1

2 4 2 2

Total

TOTAL POP EXAMINED Male Female Total

Male

URBAN Female

Total

-

-

2

3 6 3 4

289 247 196 165 146 152

-

106 84 64 59 71

178 141 112 101 87 81

23.8 62.5 33.9 28.2

8.9 19.8 11.5 24.7

15.3 36.4 20.5 26.3

6

16

495

700

1195

20.2

8.6

13.4

2 1

-

~

10

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Table 3. Age and ses distribution of thc prcvalencc of coronary hcart disease in rural (pcr 1000 population) PREVALENCE

CHD Female

Male

TOTAL POP EXAMINED Male Female Total

Total

Male

KURAL Female

Total

Age ( Y ~ s ) ~~

15-24 25-34 35-44 45-54 55-64 65 &above Total

-

~

~

~

-

-

I 1

I I

2 3

2

2 2 3 5

7

5

12

1

Of the 16 cases of CHD diagnosed in the urban area, 14 were havinganginapectorisand two werecases of myocardial infarct. In the rural area, out of 12 cases of CHD, 10 were suffering from angina pectoris and two from myocardial infarct. Table 4 shows the standardized morbidity ratio of the effect of smokingon CHD, controlling for sex in the urban community. The standardized morbidityratiowas 8.08 (95YoC14.27 to 15.3) and that for the rural community was 2.95 (95% CI 0.63 to 13.73). The attributable fraction of smoking on C H D in the urban communitywas 77%whereas that ofthe rural community was 55%.

-

l 36

-

93 54 58 69 51 46 1

253 217 164 125 86

18.5 17.2 28.9 58.8

955

1416

15.2

110

Among the urban study population, 74% of the males were smokers, whereas only 46% of the females were smokers. In the rural study population, 68%ofthe males and 55%ofthe females were smokers. The overall prevalence of smoking in the urban area was %%and that in the rural area was 59%. As seen in Table 5 , in the urban areas the present smokers are 6.63 times more likely to have CHD than non-smokers, whereas the ex-smokers are 2.5 times more likely to have CHD. This was not observed in the rural data where present smokers were three times more likely to have C H D than non-smokers, the ex-

Tablc 4. Smoking and prevalcncc of coronary heart discasc controlling for scs in urban and rural population. Area

Non-smokers CHD Total Prev*

Sex

CHD

Smokers Total Prev*

SMR**

~

URBAN

RURAL

Male Female TOTAL

0

2 2

118 323 443

0.0 6.2 4.6

4 14

335 280 613

29.85 14.29 22.84

6 4

313 520

19.17 7.69

10

833

12.0

Male Female

1

147 431

6.8 3.32

Total

2

578

3.46

I

10

.

8.08

2.95

*per 1000population **SMR = standardized morbidity ratio Table 5. Prevalence ratio of coronary hcart disease amongsrnokcrs in rural and urban population Smoking status Present smoker Ex-smoker Never smoked

URBAN Prev Ratio 95% CI 6.63 2.55 1.o

( I .48-29.72)

(0.43-15.16)

KURAL 95%CI Prev Ratio 3.09 4.09 1.o

-

389 3 10 218 I68 I94 I37

(0.63-1 5.24) (0.75- 16.45)

-

6.1 9.1 8.0 23.3 5.28

-

-

9.2 1 1.9 15.5

36.5 8.5

smokers were seen to be slightly more likely to have CHD (prev ratio 4.09). The standardized morbidity ratio of the effect of obesity (body mass index 21 and above) on the prevalence of CHD, controlling for agein theurbancommunity,was 1.81 (95% CI 0.52 to 6.31) and that seen in the rural community was 0.49 (95% CI 0.14 to 1.68). The attributable fraction of obesity on C H D among the urban population was 27.9% (Table 6 ) . As seen in Table 7, the proportion of the population with a body mass index over 26 is greater in the urban population (10.71%) as compared to the rural population where only 4.16% are above this cut-off point. This shows that the urban population is more obese than the rural population (p < 0.0005). T h e age-standardized prevalence rate for HT in urban areas was 49 per 1000 population which was observed to be much lower than that the 57.9 per 1000 population of the rural area (Tables 8 and 9). With the exception of the 55-64 years age group, in all the remainingagecategories, the prevalence of HT was seen to be higher in the rural population. The prevalence ratio of H T among males and females was 1.36 and 1.79 respectively in the urban and rural areas which shows that males are more likely to have HT than females. Table 10shows the standardized mortality ratio for the effect ofsmoking on the prevalence of HT, controlling for age in the urban population. The standardized mortality ratio was 1.18 (95% CI 0.61 to 2.28) in the urban area and that for the rural

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Asia-Pacific Journal of Public Health 199211993 Vol. 6 No. 4

'Table 6. Prevalence of coronary heart disease among obese individuals in urban and rural populations, controlling for age

URBAN Obesity (Body Mass Index) 20&> 21 & >

A s (yrs)

CHD Non-Ds Prev* 15-44 45-54 55-64 65&>

TOTAL

RURAL Obesity (Body Mass Index) 20&> 21 & >

CHD Non-Ds Prev*

CHD Non-Ds Prev*

I 2

409 66 56 74

4.89 15.38 17.54 27.03

5 2 2

65 100 89 78

15.15 50.0 22.47 25.64

2 2 3 3

638 109 136 106

3.13 18.35 22.06 28.3

6

605

9.92

10

338

17.21

10

989

11.0

2 1

1

CIlD Non-Ds Prev*

2

279 59 58 31

0.0 0.0 0.0 64.52

2

427

4.68

0 0 0

*per 1000 population 'l'ablc 7. Body RIass Index distribution in rural and urban populations

Body Mass lndex

Urban 125 480 462

10-15 16-20 21-25 26-30 31 & >

Rural

%

( 1 0.46)

202 787 354 47 26

(14.27) (55.5 7) (25.0 ) ( 3.32) ( 1.84)

(40.17) (38.66) ( 8.37) ( 2.34)

100

28

Total

%

1195

1416

Table 8. Age and sex distributionofthe prevalenceof hypertension in disease inurban population (per 1000 population)

HYPERTENSION

Age(yrs)

TOTAL POP. URBAN PKEVALENCE EXAMINED Male Female Total Male Female Total Male Female Total

15-24 25-34 35-44 45-54 55-64 65&above

3 3 9 10

TOTAL

25

-

-

-

4 10 17 20

111 106 84 64 59 71

178 141 112

51

495

700

-

-

1

7 8 10 26

101

87 81

289 247 196 35.7 165 46.9 146 152.5 152 140.8 1195 50.5

-

-

-

-

8.9 69.3 92.0 123.5

20.4 60.6 116.4 131.6

37.1

42.7

Table 9. Age and sex distribution of the prevalence of hypertension in rural population (per 1000 population)

HYPERTENSION

Age(yrs) ~

TOTAL POP. RURAL PREVALENCE EXAMINED Male Fernale Total Male Female Total Male Female Total

~~~~~

15-24 25-34 35-44 45-54 55-64 65&above

TOTAL

-

-

6 10 10 12

11

38

-

~

253 217 164

12 12 9

17 22 22 21

136 93 54 58 69 51

44

82

461

955

-

110

125 86

389 310 218 1 1 1 . 1 168 17.2 194 144.9 137 235.3 1416

82.4

-

-

-

-

67.1 109.1 96.0 104.7

77.9 131.0 113.4 153.3

46.1

57.9

population was 7.36 (95% CI 4.94 to 10.96). I t was observed that in the urban areas 41.56% of the respondents were non-smokers whereas in the rural areas non-smokers made up only 3 1.3 1 %. The prevalence of HT was observed to be higher in the present and ex-smoker groups in both the urban and rural populations, but the prevalence ratio was very high in the rural community (Table 1 1). As seen in Table 12, the internally standardized morbidity ratio controlling for age in urban area was 1.03 (95% CI .6 to 1.77) and that for theruralareait was 1.76(95%CIO.97 to 3.19). This shows that obesity was not a major factor in the cause of H T in both the urban and rural areas where this study was conducted. The prevalence of rheumatic heart disease was seen to be higher in the rural areas( 19.07 per 1000 pop) as compared to theurban areas(5.86per 1000 pop). It was also seen that in both the urban and rural areas, the prevalenceofrheumatic heart disease was higher in females (Table 13).

Discussion Prevalence of coronary heart disease was found to be 13.38 per 1000 popu-

lation over 15 years of age in Yangon City and 8.47 per 1000 population over 15 years in the rural area of Taiklqyi Township. This shows that CHD is a problem in both the urban and rural comrnunitiesofourcountry though the prevalence is higher in the urban areas even when age is standardized (urban 12.03/1000 to rural 8.47/1000 for those over 15 years).

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Table 10. Effectofsmokingonprevalenceofh~ptrtensioncuntrollingforageinurban and rural populations (per 1000 pop)

Area URBAN

KURAL

age

HT

15-44 45-54 55-64 65&> TOTAL

3 3 4

Non-smokers Total Prev*

1

11

325 36 43 34 438

3.08 83.33 69.77 117.65 25.11

-

15-44 45-54 55-64 65&>

0 2 0’ 0

313 25 26 17

80.0

Total

2

381

HT 3 7

Smokers Total Rev*

11

320 106 90

12 33

616

100

SMR**

9.38 66.04 122.22 120.0 56.6

462 124 150

-

16 20 20 17

100

34.63 161.29 133.33 170.0

5.25

73

836

95.67

-

1.18

7.36

*prev = prevalence per 1000 pop. SMR**= standardized morbidity ratio Table 11. Prevalence ratio of hypertension among smokers in rural and urban populations

Smoking status

URBAN 95% CI

PR Present smoker Ex-smoker Never smoked

I . 19 to 4.94 0.42 to 7.03

2.43 1.72

RURAL 95% CI

PR

7.6 to 70.55 3.77 to 66.68

17.27 15.85 I .o

1.o

The peak prevalence of CHD was also seen in the 45 to 54 years age group. Since premature atherosclerosis is due to exposure to multiple risk factors’ the difference in the prevalence is very likely due to differing lifestyles between the two communities. Smoking emerged as the major risk factor in this study. The sexstandardized prevalence ratio of the effect of smoking on CHD was 8.08 (95% CI 4.27 to 15.3) in the urban population. This high association with smokingwas not observed in the rural population. In looking into the different categories of smokers (present and ex-smokers), the urban present smoker group had a very high prevalence ratio of 6.63. T h e attributable fraction of smoking on CHD in the urban area was 77% whereas for the rural area it was only 55%. Although the smokinghabit wasalmost the same in these two communities, the type of smoke may account for the difference. In Kyaw Tint et al’s14 study, urbanites were seen to be smoking more

Table 12. Prevalence of hypertensionamong obese individuals among urban and rural populations, controlling for age

URBAN Obesity (Body Mass Index) 20&> 21 & >

Age ( Y 4

RURAL Obesity (Body Mass Index) 20&> 21 & >

HT

Total

Prev

HT

Total

Prev

HT

Total

Prev

HT

Total

Prev

15-44 45-54 55-64 65&>

2 4 9 7

430 69 57 78

4.7 58.0 157.9 98.6

2 6 8 13

302 96 89 81

6.62 62.5 89.89 160.49

10 I1 12 17

640 109 136 106

15.6 100.9 88.24 160.37

7 I1 10 4

277 49 52 27

25.3 224.49 192.31 148.15

Total

22

634

34.7

29

568

51.06

50

991

50.45

32

405

79.01

Tablc 13. Age and ses distribution of rheumatic heart disease in urban areas

Age(yrs)

Male

KHD Female

Total

-

-

-

2

2

TOTAL POP. EXAMINED Male Female Total

~

.

Under 25 26-35 36-45 46-55 56&>

-

-

2

-

-

1

1

2

4

I18 106 80 92 104

5

7

500

188 139 I12 137 112

306 245 I92 229 216

688

1188

URBAN PREVALENCE Male Female Total

-

-

-

14.18

8.1

18.87

7.25 17.54

4.35 18.18

3.98

7.22

5.86

-

-

-

-

~~

Total

2

I92

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Asia-Pacific Journal of Public Health 199211993 Vol. 6 No. 4 Table 14. Age and sex distribution of rheumatic heart disease in rural areas Age(yrs)

Male

RHD Female

Total

TOTAL POP. EXAMINED Male Female Total

RURAL PREVALENCE

Male

Female

Total 9.7 1 40.4 15.79 7.69 23.35 19.07

~~~

Under 25 26- 35 36-45 46-55

1 1

3 11

-

56&>

Total

2

3 2 4

4 12 3 2 6

88 47 85 115

264 197 140 173 136

408 285 187 258 25 1

17.09

11.24 52.88 20.98 11.43 28.57

4

23

27

479

910

1389

8.28

24.65

-

cigarettes and cigarette smoking was found to be linked to CHD more than other forms of nicotine intake”. The prevalence of hypertension was 42.68 and 57.91 per 1000 population over 15 years of age in urban and rural areasrespectively. Theprevalence observed in this study was much lower than that seen in the H T survey conducted in the five divisions of M y a n m d g where the prevalence was 167.1 and 124.6 per 1000 population over 30 years. This higher prevalence observed could be due to the much lower cut-off point taken for H T (140/90), the examination of the over-30s population, and the fact that in the rural areas individuals attending hospital OPDs were used as the study subjects. HT was found to be more prevalent in the rural than urban areas20-22and although this pattern was seen within other populations, in most instances the reverse held true. In Japan more hypertensives were found in the rural than in the urban areas whereas in Korea the reverse pattern was seen23.The prevalenceof HTwas found to be higher in the rural areas even when age standardized (urban 49/1000 pop over 15 years). This could be due to the rural people eating a diet which is high in salt content such as dried fish and fish paste. Per capita consumption of salt in Myanmar is high (8 gm)2Jas it is in most ruralcommunities in Asiawhere the fish paste containing a high salt content forms the main source ofprotein. A recent large-scale multinational study” showed the independent effects of high body mass index, high alcohol intake, and a weaker but nevertheless significant effect of salt on blood pressure. The prevalence of hypertension

144

was seen to be high in males in both the urban and rural communities. This male preponderance was also observed in other studies3. Though the overall prevalence of H T was seen to be high in males, in the 45 to 54 years age group, females were found to be suffering from HT more than males. This pattern was observed in both urban and rural areas. Standardized mortality ratio of the effect of smoking on the prevalence of HT, controlling for age was 7.36 (95% CI 4.94 to 10.96) in the rural population. In the rural area, smoking was also seen to be highly associated with HT among smokers (prev. ratio 17.27) and ex-smokers (prev. ratio 15.85). This association was weakly observed in the urban population of present smokers only (prevalence ratio 2.43). In this study, smokingwasshown to have a positive effect on the blood pressure and although smoking does cause a short-term rise of the blood pressure2’, hypertension was found to be less among smokers because of the weight loss associated with chronic smoking2’. In both the urban and rural populations, obesity (body mass index over 21 and above) was observed to have no effect on the prevalence of CHD as well as HT. This could mean that obesity does not playa major role in theetiologyofthese two diseases in our country. The distribution ofbody mass index was seen to be statistically different in the urban and rural populations. The urban population was observed to be more obcse compared to the rural population. This could be attributed to the sedentary lifestyles and differences in the dietary intake ofthe urban population.

6.89 11.24

-

Rheumatic heart disease prevalence was observed to be high among the females in both urban and rural populations. The prevalence of RHD was also much higher in rural areas ( 1 9.07 per 1000 population over age 15 years) compared to the urban area (5.86per 1000populationoverage 15 years). Since KHD is associated with over-crowding, poverty and lack of proper medical care, the lower prevalence rate in urban areas may be due to better accessibility to medicalcare. A similar difference was noted in Aye et al’s26 study in Myanmar and in India2’ where the prevalence of rheumatic heart disease was observed to be higher in the rural areas. Conclusion It appears that cardiovascular diseases are a health problem in both the urban and rural communities of Sanchaung, Latha, Pabedanand Hmawbi Townships. Coronary heart disease was seen to be more prevalent in the urban townships than in the rural Hmawbi Township, but it was seen that hypertension and rheumatic heart diseases were more prevalent in the rural township of Hmawbi. Obesity, which has been blamed as the major risk factor for CHD and H T in the developed countries, was seen to be not a risk factor in the study townships though smoking was seen to be a major risk factor. Acknowledgments The authors would like to express their gratitude to all thosewho helped in the conduct ofthis study, in particular to the staff nurses from the cardiac wardoftheYangonGenera1 Hospital, the basic health workers from

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the three urban townships of Latha, Pabedan and Sanchaung and that of rural I-Imawbi Township. Finally, the authors would like to thank the community mcmbcrs from the study townships who willingly participated in this study.

2.

3. 4.

5.

6.

7.

8.

10. 11.

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